diff options
Diffstat (limited to 'erts/doc/src/erlang.xml')
| -rw-r--r-- | erts/doc/src/erlang.xml | 8358 |
1 files changed, 5054 insertions, 3304 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index e02e4cbbc9..e4d5e6e77a 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -1,23 +1,24 @@ -<?xml version="1.0" encoding="latin1" ?> +<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE erlref SYSTEM "erlref.dtd"> <erlref> <header> <copyright> - <year>1996</year><year>2013</year> + <year>1996</year><year>2015</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> - The contents of this file are subject to the Erlang Public License, - Version 1.1, (the "License"); you may not use this file except in - compliance with the License. You should have received a copy of the - Erlang Public License along with this software. If not, it can be - retrieved online at http://www.erlang.org/. + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 - Software distributed under the License is distributed on an "AS IS" - basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See - the License for the specific language governing rights and limitations - under the License. + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. </legalnotice> @@ -29,36 +30,107 @@ <file>erlang.xml</file> </header> <module>erlang</module> - <modulesummary>The Erlang BIFs</modulesummary> + <modulesummary>The Erlang BIFs.</modulesummary> <description> - <p>By convention, most built-in functions (BIFs) are seen as being - in the module <c>erlang</c>. A number of the BIFs are viewed more + <p>By convention, most Built-In Functions (BIFs) are seen as being + in this module. Some of the BIFs are viewed more or less as part of the Erlang programming language and are - <em>auto-imported</em>. Thus, it is not necessary to specify - the module name and both the calls <c>atom_to_list(Erlang)</c> and - <c>erlang:atom_to_list(Erlang)</c> are identical.</p> - <p>In the text, auto-imported BIFs are listed without module prefix. + <em>auto-imported</em>. Thus, it is not necessary to specify the + module name. For example, the calls <c>atom_to_list(Erlang)</c> + and <c>erlang:atom_to_list(Erlang)</c> are identical.</p> + <p>Auto-imported BIFs are listed without module prefix. BIFs listed with module prefix are not auto-imported.</p> - <p>BIFs may fail for a variety of reasons. All BIFs fail with + <p>BIFs can fail for various reasons. All BIFs fail with reason <c>badarg</c> if they are called with arguments of an - incorrect type. The other reasons that may make BIFs fail are - described in connection with the description of each individual - BIF.</p> - <p>Some BIFs may be used in guard tests, these are marked with + incorrect type. The other reasons are described in the + description of each individual BIF.</p> + <p>Some BIFs can be used in guard tests and are marked with "Allowed in guard tests".</p> </description> <datatypes> <datatype> - <name><marker id="type-ext_binary">ext_binary()</marker></name> + <name>ext_binary()</name> <desc> + <marker id="type-ext_binary"></marker> <p>A binary data object, structured according to the Erlang external term format.</p> </desc> </datatype> + <datatype> <name name="timestamp"></name> - <desc><p>See <seealso marker="#now/0">now/0</seealso>.</p> + <desc><p>See <seealso marker="#timestamp/0">erlang:timestamp/0</seealso>.</p> + </desc> + </datatype> + <datatype> + <name name="time_unit"></name> + <desc><p><marker id="type_time_unit"/> + Supported time unit representations:</p> + <taglist> + <tag><c>PartsPerSecond :: integer() >= 1</c></tag> + <item><p>Time unit expressed in parts per second. That is, + the time unit equals <c>1/PartsPerSecond</c> second.</p></item> + + <tag><c>seconds</c></tag> + <item><p>Symbolic representation of the time unit + represented by the integer <c>1</c>.</p></item> + + <tag><c>milli_seconds</c></tag> + <item><p>Symbolic representation of the time unit + represented by the integer <c>1000</c>.</p></item> + + <tag><c>micro_seconds</c></tag> + <item><p>Symbolic representation of the time unit + represented by the integer <c>1000000</c>.</p></item> + + <tag><c>nano_seconds</c></tag> + <item><p>Symbolic representation of the time unit + represented by the integer <c>1000000000</c>.</p></item> + + <tag><c>native</c></tag> + <item><p>Symbolic representation of the native time unit + used by the Erlang runtime system.</p> + + <p>The <c>native</c> time unit is determined at + runtime system start, and remains the same until + the runtime system terminates. If a runtime system + is stopped and then started again (even on the same + machine), the <c>native</c> time unit of the new + runtime system instance can differ from the + <c>native</c> time unit of the old runtime system + instance.</p> + + <p>One can get an approximation of the <c>native</c> + time unit by calling <c>erlang:convert_time_unit(1, + seconds, native)</c>. The result equals the number + of whole <c>native</c> time units per second. In case + the number of <c>native</c> time units per second does + not add up to a whole number, the result is rounded downwards.</p> + + <note> + <p>The value of the <c>native</c> time unit gives + you more or less no information at all about the + quality of time values. It sets a limit for + the + <seealso marker="time_correction#Time_Resolution">resolution</seealso> + as well as for the + <seealso marker="time_correction#Time_Precision">precision</seealso> + of time values, + but it gives absolutely no information at all about the + <seealso marker="time_correction#Time_Accuracy">accuracy</seealso> + of time values. The resolution of the <c>native</c> time + unit and the resolution of time values can differ + significantly.</p> + </note> + </item> + + </taglist> + + <p>The <c>time_unit/0</c> type may be extended. Use + <seealso marker="#convert_time_unit/3"><c>erlang:convert_time_unit/3</c></seealso> + in order to convert time values between time units.</p> + </desc> </datatype> </datatypes> @@ -67,12 +139,15 @@ <func> <name name="abs" arity="1" clause_i="1"/> <name name="abs" arity="1" clause_i="2"/> - <type variable="Float" name_i="1"/> - <type variable="Int" name_i="2"/> - <fsummary>Arithmetical absolute value</fsummary> - <desc> - <p>Returns an integer or float which is the arithmetical - absolute value of <c><anno>Float</anno></c> or <c><anno>Int</anno></c>.</p> + <fsummary>Arithmetical absolute value.</fsummary> + <type> + <v>Float = float()</v> + <v>Int = integer()</v> + </type> + <desc> + <p>Returns an integer or float that is the arithmetical + absolute value of <c><anno>Float</anno></c> or + <c><anno>Int</anno></c>, for example:</p> <pre> > <input>abs(-3.33).</input> 3.33 @@ -81,206 +156,214 @@ <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="adler32" arity="1"/> - <fsummary>Compute adler32 checksum</fsummary> + <fsummary>Computes adler32 checksum.</fsummary> <desc> - <p>Computes and returns the adler32 checksum for <c><anno>Data</anno></c>.</p> + <p>Computes and returns the adler32 checksum for + <c><anno>Data</anno></c>.</p> </desc> </func> + <func> <name name="adler32" arity="2"/> - <fsummary>Compute adler32 checksum</fsummary> + <fsummary>Computes adler32 checksum.</fsummary> <desc> - <p>Continue computing the adler32 checksum by combining - the previous checksum, <c><anno>OldAdler</anno></c>, with the checksum of - <c><anno>Data</anno></c>.</p> - <p>The following code:</p> - <code> - X = erlang:adler32(Data1), - Y = erlang:adler32(X,Data2). - </code> - <p>- would assign the same value to <c>Y</c> as this would:</p> - <code> - Y = erlang:adler32([Data1,Data2]). - </code> + <p>Continues computing the adler32 checksum by combining + the previous checksum, <c><anno>OldAdler</anno></c>, with + the checksum of <c><anno>Data</anno></c>.</p> + <p>The following code:</p> + <code> + X = erlang:adler32(Data1), + Y = erlang:adler32(X,Data2).</code> + <p>assigns the same value to <c>Y</c> as this:</p> + <code> + Y = erlang:adler32([Data1,Data2]).</code> </desc> </func> + <func> <name name="adler32_combine" arity="3"/> - <fsummary>Combine two adler32 checksums</fsummary> - <desc> - <p>Combines two previously computed adler32 checksums. - This computation requires the size of the data object for - the second checksum to be known.</p> - <p>The following code:</p> - <code> - Y = erlang:adler32(Data1), - Z = erlang:adler32(Y,Data2). - </code> - <p>- would assign the same value to <c>Z</c> as this would:</p> - <code> - X = erlang:adler32(Data1), - Y = erlang:adler32(Data2), - Z = erlang:adler32_combine(X,Y,iolist_size(Data2)). - </code> + <fsummary>Combines two adler32 checksums.</fsummary> + <desc> + <p>Combines two previously computed adler32 checksums. + This computation requires the size of the data object for + the second checksum to be known.</p> + <p>The following code:</p> + <code> + Y = erlang:adler32(Data1), + Z = erlang:adler32(Y,Data2).</code> + <p>assigns the same value to <c>Z</c> as this:</p> + <code> + X = erlang:adler32(Data1), + Y = erlang:adler32(Data2), + Z = erlang:adler32_combine(X,Y,iolist_size(Data2)).</code> </desc> </func> + <func> <name name="append_element" arity="2"/> - <fsummary>Append an extra element to a tuple</fsummary> - <desc> - <p>Returns a new tuple which has one element more than - <c><anno>Tuple1</anno></c>, and contains the elements in <c><anno>Tuple1</anno></c> - followed by <c><anno>Term</anno></c> as the last element. Semantically - equivalent to - <c>list_to_tuple(tuple_to_list(<anno>Tuple1</anno>) ++ [<anno>Term</anno>])</c>, but much - faster.</p> + <fsummary>Appends an extra element to a tuple.</fsummary> + <desc> + <p>Returns a new tuple that has one element more than + <c><anno>Tuple1</anno></c>, and contains the elements in + <c><anno>Tuple1</anno></c> + followed by <c><anno>Term</anno></c> as the last element. + Semantically equivalent to + <c>list_to_tuple(tuple_to_list(<anno>Tuple1</anno>) ++ + [<anno>Term</anno>])</c>, but much faster.</p> + <p>Example:</p> <pre> > <input>erlang:append_element({one, two}, three).</input> {one,two,three}</pre> </desc> </func> + <func> <name name="apply" arity="2"/> - <fsummary>Apply a function to an argument list</fsummary> + <fsummary>Applies a function to an argument list.</fsummary> <desc> - <p>Call a fun, passing the elements in <c><anno>Args</anno></c> as - arguments.</p> - <p>Note: If the number of elements in the arguments are known at - compile-time, the call is better written as + <p>Calls a fun, passing the elements in <c><anno>Args</anno></c> + as arguments.</p> + <p>If the number of elements in the arguments are known at + compile time, the call is better written as <c><anno>Fun</anno>(Arg1, Arg2, ... ArgN)</c>.</p> <warning> <p>Earlier, <c><anno>Fun</anno></c> could also be given as <c>{Module, Function}</c>, equivalent to - <c>apply(Module, Function, Args)</c>. This usage is - deprecated and will stop working in a future release of - Erlang/OTP.</p> + <c>apply(Module, Function, Args)</c>. This use is + deprecated and will stop working in a future release.</p> </warning> </desc> </func> + <func> <name name="apply" arity="3"/> - <fsummary>Apply a function to an argument list</fsummary> + <fsummary>Applies a function to an argument list.</fsummary> <desc> <p>Returns the result of applying <c>Function</c> in - <c><anno>Module</anno></c> to <c><anno>Args</anno></c>. The applied function must + <c><anno>Module</anno></c> to <c><anno>Args</anno></c>. + The applied function must be exported from <c>Module</c>. The arity of the function is the length of <c>Args</c>.</p> + <p>Example:</p> <pre> > <input>apply(lists, reverse, [[a, b, c]]).</input> -[c,b,a]</pre> - <p><c>apply</c> can be used to evaluate BIFs by using - the module name <c>erlang</c>.</p> - <pre> +[c,b,a] > <input>apply(erlang, atom_to_list, ['Erlang']).</input> "Erlang"</pre> - <p>Note: If the number of arguments are known at compile-time, + <p>If the number of arguments are known at compile time, the call is better written as <c><anno>Module</anno>:<anno>Function</anno>(Arg1, Arg2, ..., ArgN)</c>.</p> <p>Failure: <c>error_handler:undefined_function/3</c> is called if the applied function is not exported. The error handler can be redefined (see <seealso marker="#process_flag/2">process_flag/2</seealso>). - If the <c>error_handler</c> is undefined, or if the user has + If <c>error_handler</c> is undefined, or if the user has redefined the default <c>error_handler</c> so the replacement module is undefined, an error with the reason <c>undef</c> is generated.</p> </desc> </func> + <func> <name name="atom_to_binary" arity="2"/> - <fsummary>Return the binary representation of an atom</fsummary> - <desc> - <p>Returns a binary which corresponds to the text - representation of <c><anno>Atom</anno></c>. If <c><anno>Encoding</anno></c> - is <c>latin1</c>, there will be one byte for each character - in the text representation. If <c><anno>Encoding</anno></c> is - <c>utf8</c> or - <c>unicode</c>, the characters will be encoded using UTF-8 - (meaning that characters from 16#80 up to 0xFF will be - encoded in two bytes).</p> - - <note><p>Currently, <c>atom_to_binary(<anno>Atom</anno>, latin1)</c> can - never fail because the text representation of an atom can only contain - characters from 0 to 16#FF. In a future release, the text representation - of atoms might be allowed to contain any Unicode character - and <c>atom_to_binary(<anno>Atom</anno>, latin1)</c> will fail if the - text representation for the <c><anno>Atom</anno></c> contains a Unicode - character greater than 16#FF.</p></note> - + <fsummary>Returns the binary representation of an atom.</fsummary> + <desc> + <p>Returns a binary corresponding to the text + representation of <c><anno>Atom</anno></c>. + If <c><anno>Encoding</anno></c> + is <c>latin1</c>, there is one byte for each character + in the text representation. If <c><anno>Encoding</anno></c> is + <c>utf8</c> or + <c>unicode</c>, the characters are encoded using UTF-8 + (that is, characters from 128 through 255 are + encoded in two bytes).</p> + <note><p><c>atom_to_binary(<anno>Atom</anno>, latin1)</c> never + fails because the text representation of an atom can only + contain characters from 0 through 255. In a future release, + the text representation + of atoms can be allowed to contain any Unicode character and + <c>atom_to_binary(<anno>Atom</anno>, latin1)</c> will then fail if the + text representation for <c><anno>Atom</anno></c> contains a Unicode + character greater than 255.</p></note> + <p>Example:</p> <pre> > <input>atom_to_binary('Erlang', latin1).</input> <<"Erlang">></pre> </desc> </func> + <func> <name name="atom_to_list" arity="1"/> - <fsummary>Text representation of an atom</fsummary> + <fsummary>Text representation of an atom.</fsummary> <desc> - <p>Returns a string which corresponds to the text - representation of <c><anno>Atom</anno></c>.</p> + <p>Returns a string corresponding to the text + representation of <c><anno>Atom</anno></c>, for example:</p> <pre> > <input>atom_to_list('Erlang').</input> "Erlang"</pre> </desc> </func> + <func> <name name="binary_part" arity="2"/> - <fsummary>Extracts a part of a binary</fsummary> + <fsummary>Extracts a part of a binary.</fsummary> <desc> - <p>Extracts the part of the binary described by <c><anno>PosLen</anno></c>.</p> - - <p>Negative length can be used to extract bytes at the end of a binary:</p> - + <p>Extracts the part of the binary described by + <c><anno>PosLen</anno></c>.</p> + <p>Negative length can be used to extract bytes at the end + of a binary, for example:</p> <code> 1> Bin = <<1,2,3,4,5,6,7,8,9,10>>. 2> binary_part(Bin,{byte_size(Bin), -5}). -<<6,7,8,9,10>> -</code> - - <p>If <c><anno>PosLen</anno></c> in any way references outside the binary, a <c>badarg</c> exception is raised.</p> - - <p><c><anno>Start</anno></c> is zero-based, i.e.:</p> +<<6,7,8,9,10>></code> + <p>Failure: <c>badarg</c> if <c><anno>PosLen</anno></c> in any way + references outside the binary.</p> + <p><c><anno>Start</anno></c> is zero-based, that is:</p> <code> 1> Bin = <<1,2,3>> 2> binary_part(Bin,{0,2}). -<<1,2>> -</code> - - <p>See the STDLIB module <c>binary</c> for details about the <c><anno>PosLen</anno></c> semantics.</p> - +<<1,2>></code> + <p>For details about the <c><anno>PosLen</anno></c> semantics, see the + <seealso marker="stdlib:binary">binary</seealso> + manual page in <c>STDLIB</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="binary_part" arity="3"/> - <fsummary>Extracts a part of a binary</fsummary> + <fsummary>Extracts a part of a binary.</fsummary> <desc> - <p>The same as <c>binary_part(<anno>Subject</anno>, {<anno>Start</anno>, <anno>Length</anno>})</c>.</p> - + <p>The same as <c>binary_part(<anno>Subject</anno>, + {<anno>Start</anno>, <anno>Length</anno>})</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="binary_to_atom" arity="2"/> - <fsummary>Convert from text representation to an atom</fsummary> + <fsummary>Converts from text representation to an atom.</fsummary> <desc> <p>Returns the atom whose text representation is - <c><anno>Binary</anno></c>. If <c><anno>Encoding</anno></c> is <c>latin1</c>, no - translation of bytes in the binary is done. If <c><anno>Encoding</anno></c> - is <c>utf8</c> or <c>unicode</c>, the binary must contain - valid UTF-8 sequences; furthermore, only Unicode characters up - to 0xFF are allowed.</p> - - <note><p><c>binary_to_atom(<anno>Binary</anno>, utf8)</c> will fail if - the binary contains Unicode characters greater than 16#FF. - In a future release, such Unicode characters might be allowed - and <c>binary_to_atom(<anno>Binary</anno>, utf8)</c> - will not fail in that case. For more information on Unicode support in atoms - see <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8 encoded atoms</seealso> - in the chapter about the external term format in the ERTS User's Guide.</p></note> - + <c><anno>Binary</anno></c>. + If <c><anno>Encoding</anno></c> is <c>latin1</c>, no + translation of bytes in the binary is done. + If <c><anno>Encoding</anno></c> + is <c>utf8</c> or <c>unicode</c>, the binary must contain + valid UTF-8 sequences. Only Unicode characters up + to 255 are allowed.</p> + <note><p><c>binary_to_atom(<anno>Binary</anno>, utf8)</c> fails if + the binary contains Unicode characters greater than 255. + In a future release, such Unicode characters can be allowed + and <c>binary_to_atom(<anno>Binary</anno>, utf8)</c> does then not fail. + For more information on Unicode support in atoms, see the + <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8 + encoded atoms</seealso> + in Section "External Term Format" in the User's Guide.</p></note> + <p>Examples:</p> <pre> > <input>binary_to_atom(<<"Erlang">>, latin1).</input> 'Erlang' @@ -290,20 +373,24 @@ called as binary_to_atom(<<208,128>>,utf8)</pre> </desc> </func> + <func> <name name="binary_to_existing_atom" arity="2"/> - <fsummary>Convert from text representation to an atom</fsummary> + <fsummary>Converts from text representation to an atom.</fsummary> <desc> - <p>Works like <seealso marker="#binary_to_atom/2">binary_to_atom/2</seealso>, - but the atom must already exist.</p> - <p>Failure: <c>badarg</c> if the atom does not already exist.</p> + <p>As + <seealso marker="#binary_to_atom/2">binary_to_atom/2</seealso>, + but the atom must exist.</p> + <p>Failure: <c>badarg</c> if the atom does not exist.</p> </desc> </func> + <func> <name name="binary_to_float" arity="1"/> - <fsummary>Convert from text representation to a float</fsummary> + <fsummary>Converts from text representation to a float.</fsummary> <desc> - <p>Returns the float whose text representation is <c><anno>Binary</anno></c>.</p> + <p>Returns the float whose text representation is + <c><anno>Binary</anno></c>, for example:</p> <pre> > <input>binary_to_float(<<"2.2017764e+0">>).</input> 2.2017764</pre> @@ -311,12 +398,13 @@ representation of a float.</p> </desc> </func> + <func> <name name="binary_to_integer" arity="1"/> - <fsummary>Convert from text representation to an integer</fsummary> + <fsummary>Converts from text representation to an integer.</fsummary> <desc> <p>Returns an integer whose text representation is - <c><anno>Binary</anno></c>.</p> + <c><anno>Binary</anno></c>, for example:</p> <pre> > <input>binary_to_integer(<<"123">>).</input> 123</pre> @@ -324,12 +412,13 @@ representation of an integer.</p> </desc> </func> + <func> <name name="binary_to_integer" arity="2"/> - <fsummary>Convert from text representation to an integer</fsummary> + <fsummary>Converts from text representation to an integer.</fsummary> <desc> <p>Returns an integer whose text representation in base - <c><anno>Base</anno></c> is <c><anno>Binary</anno></c>.</p> + <c><anno>Base</anno></c> is <c><anno>Binary</anno></c>, for example:</p> <pre> > <input>binary_to_integer(<<"3FF">>, 16).</input> 1023</pre> @@ -337,93 +426,101 @@ representation of an integer.</p> </desc> </func> + <func> <name name="binary_to_list" arity="1"/> - <fsummary>Convert a binary to a list</fsummary> + <fsummary>Converts a binary to a list.</fsummary> <desc> - <p>Returns a list of integers which correspond to the bytes of + <p>Returns a list of integers corresponding to the bytes of <c><anno>Binary</anno></c>.</p> </desc> </func> + <func> <name name="binary_to_list" arity="3"/> - <fsummary>Convert part of a binary to a list</fsummary> - <type_desc variable="Start">1..byte_size(<anno>Binary</anno>)</type_desc> + <fsummary>Converts part of a binary to a list.</fsummary> + <type_desc variable="Start">1..byte_size(<c><anno>Binary</anno></c>)</type_desc> <desc> <p>As <c>binary_to_list/1</c>, but returns a list of integers corresponding to the bytes from position <c><anno>Start</anno></c> to - position <c><anno>Stop</anno></c> in <c><anno>Binary</anno></c>. Positions in the + position <c><anno>Stop</anno></c> in <c><anno>Binary</anno></c>. + The positions in the binary are numbered starting from 1.</p> - - <note><p>This function's indexing style of using one-based indices for - binaries is deprecated. New code should use the functions in - the STDLIB module <c>binary</c> instead. They consequently - use the same (zero-based) style of indexing.</p></note> + <note><p>The one-based indexing for binaries used by + this function is deprecated. New code is to use + <seealso marker="stdlib:binary#bin_to_list/3">binary:bin_to_list/3</seealso> + in <c>STDLIB</c> instead. All functions in module + <c>binary</c> consistently use zero-based indexing.</p></note> </desc> </func> + <func> <name name="bitstring_to_list" arity="1"/> - <fsummary>Convert a bitstring to a list</fsummary> + <fsummary>Converts a bitstring to a list.</fsummary> <desc> - <p>Returns a list of integers which correspond to the bytes of - <c><anno>Bitstring</anno></c>. If the number of bits in the binary is not - divisible by 8, the last element of the list will be a bitstring - containing the remaining bits (1 up to 7 bits).</p> + <p>Returns a list of integers corresponding to the bytes of + <c><anno>Bitstring</anno></c>. If the number of bits in the binary + is not divisible by 8, the last element of the list is a bitstring + containing the remaining 1-7 bits.</p> </desc> </func> + <func> <name name="binary_to_term" arity="1"/> - <fsummary>Decode an Erlang external term format binary</fsummary> + <fsummary>Decodes an Erlang external term format binary.</fsummary> <desc> - <p>Returns an Erlang term which is the result of decoding - the binary object <c><anno>Binary</anno></c>, which must be encoded + <p>Returns an Erlang term that is the result of decoding + binary object <c><anno>Binary</anno></c>, which must be encoded according to the Erlang external term format.</p> - <warning> - <p>When decoding binaries from untrusted sources, consider using - <c>binary_to_term/2</c> to prevent denial of service attacks.</p> - </warning> - <p>See also - <seealso marker="#term_to_binary/1">term_to_binary/1</seealso> - and - <seealso marker="#binary_to_term/2">binary_to_term/2</seealso>.</p> + <warning><p>When decoding binaries from untrusted sources, + consider using <c>binary_to_term/2</c> to prevent Denial + of Service attacks.</p></warning> + <p>See also + <seealso marker="#term_to_binary/1">term_to_binary/1</seealso> + and + <seealso marker="#binary_to_term/2">binary_to_term/2</seealso>.</p> </desc> </func> + <func> <name name="binary_to_term" arity="2"/> - <fsummary>Decode an Erlang external term format binary</fsummary> + <fsummary>Decodes an Erlang external term format binary.</fsummary> <desc> <p>As <c>binary_to_term/1</c>, but takes options that affect decoding of the binary.</p> <taglist> <tag><c>safe</c></tag> <item> - <p>Use this option when receiving binaries from an untrusted + <p>Use this option when receiving binaries from an untrusted source.</p> - <p>When enabled, it prevents decoding data that may be used to - attack the Erlang system. In the event of receiving unsafe - data, decoding fails with a badarg error.</p> - <p>Currently, this prevents creation of new atoms directly, - creation of new atoms indirectly (as they are embedded in - certain structures like pids, refs, funs, etc.), and creation of - new external function references. None of those resources are - currently garbage collected, so unchecked creation of them can - exhaust available memory.</p> + <p>When enabled, it prevents decoding data that can be used to + attack the Erlang system. In the event of receiving unsafe + data, decoding fails with a <c>badarg</c> error.</p> + <p>This prevents creation of new atoms directly, + creation of new atoms indirectly (as they are embedded in + certain structures, such as process identifiers, + refs, and funs), and + creation of new external function references. + None of those resources are garbage collected, so unchecked + creation of them can exhaust available memory.</p> </item> </taglist> - <p>Failure: <c>badarg</c> if <c>safe</c> is specified and unsafe data - is decoded.</p> + <p>Failure: <c>badarg</c> if <c>safe</c> is specified and unsafe + data is decoded.</p> <p>See also <seealso marker="#term_to_binary/1">term_to_binary/1</seealso>, <seealso marker="#binary_to_term/1">binary_to_term/1</seealso>, - and <seealso marker="#list_to_existing_atom/1"> - list_to_existing_atom/1</seealso>.</p> + and + <seealso marker="#list_to_existing_atom/1">list_to_existing_atom/1</seealso>.</p> </desc> </func> + <func> <name name="bit_size" arity="1"/> - <fsummary>Return the size of a bitstring</fsummary> + <fsummary>Returns the size of a bitstring.</fsummary> <desc> - <p>Returns an integer which is the size in bits of <c><anno>Bitstring</anno></c>.</p> + <p>Returns an integer that is the size in bits of + <c><anno>Bitstring</anno></c>, for example:</p> <pre> > <input>bit_size(<<433:16,3:3>>).</input> 19 @@ -432,30 +529,34 @@ <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="bump_reductions" arity="1"/> - <fsummary>Increment the reduction counter</fsummary> + <fsummary>Increments the reduction counter.</fsummary> <desc> <p>This implementation-dependent function increments the reduction counter for the calling process. In the Beam emulator, the reduction counter is normally incremented by - one for each function and BIF call, and a context switch is - forced when the counter reaches the maximum number of reductions - for a process (2000 reductions in R12B).</p> + one for each function and BIF call. A context switch is + forced when the counter reaches the maximum number of + reductions for a process (2000 reductions in OTP R12B).</p> <warning> - <p>This BIF might be removed in a future version of the Beam + <p>This BIF can be removed in a future version of the Beam machine without prior warning. It is unlikely to be implemented in other Erlang implementations.</p> </warning> </desc> </func> + <func> <name name="byte_size" arity="1"/> - <fsummary>Return the size of a bitstring (or binary)</fsummary> + <fsummary>Returns the size of a bitstring (or binary).</fsummary> <desc> - <p>Returns an integer which is the number of bytes needed to contain - <c><anno>Bitstring</anno></c>. (That is, if the number of bits in <c><anno>Bitstring</anno></c> is not - divisible by 8, the resulting number of bytes will be rounded <em>up</em>.)</p> + <p>Returns an integer that is the number of bytes needed to + contain <c><anno>Bitstring</anno></c>. That is, if the number of bits + in <c><anno>Bitstring</anno></c> is not divisible by 8, the resulting + number of bytes is rounded <em>up</em>.</p> + <p>Examples:</p> <pre> > <input>byte_size(<<433:16,3:3>>).</input> 3 @@ -464,151 +565,319 @@ <p>Allowed in guard tests.</p> </desc> </func> + <func> - <name name="cancel_timer" arity="1"/> - <fsummary>Cancel a timer</fsummary> - <desc> - <p>Cancels a timer, where <c><anno>TimerRef</anno></c> was returned by - either - <seealso marker="#send_after/3">erlang:send_after/3</seealso> - or - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>. - If the timer is there to be removed, the function returns - the time in milliseconds left until the timer would have expired, - otherwise <c>false</c> (which means that <c><anno>TimerRef</anno></c> was - never a timer, that it has already been cancelled, or that it - has already delivered its message).</p> + <name name="cancel_timer" arity="2"/> + <fsummary>Cancels a timer.</fsummary> + <desc> + <p> + Cancels a timer that has been created by + <seealso marker="#start_timer/4"><c>erlang:start_timer()</c></seealso>, + or <seealso marker="#send_after/4"><c>erlang:send_after()</c></seealso>. + <c><anno>TimerRef</anno></c> identifies the timer, and + was returned by the BIF that created the timer. + </p> + <p>Available <c><anno>Option</anno></c>s:</p> + <taglist> + <tag><c>{async, Async}</c></tag> + <item> + <p> + Asynchronous request for cancellation. <c>Async</c> + defaults to <c>false</c> which will cause the + cancellation to be performed synchronously. When + <c>Async</c> is set to <c>true</c>, the cancel + operation is performed asynchronously. That is, + <c>erlang:cancel_timer()</c> will send an asynchronous + request for cancellation to the timer service that + manages the timer, and then return <c>ok</c>. + </p> + </item> + <tag><c>{info, Info}</c></tag> + <item> + <p> + Request information about the <c><anno>Result</anno></c> + of the cancellation. <c>Info</c> defaults to <c>true</c> + which means the <c><anno>Result</anno></c> is + given. When <c>Info</c> is set to <c>false</c>, no + information about the result of the cancellation + is given. When the operation is performed</p> + <taglist> + <tag>synchronously</tag> + <item> + <p> + If <c>Info</c> is <c>true</c>, the <c>Result</c> is + returned by <c>erlang:cancel_timer()</c>; otherwise, + <c>ok</c> is returned. + </p> + </item> + <tag>asynchronously</tag> + <item> + <p> + If <c>Info</c> is <c>true</c>, a message on the form + <c>{cancel_timer, <anno>TimerRef</anno>, + <anno>Result</anno>}</c> is sent to the + caller of <c>erlang:cancel_timer()</c> when the + cancellation operation has been performed; otherwise, + no message is sent. + </p> + </item> + </taglist> + </item> + </taglist> + <p> + More <c><anno>Option</anno></c>s may be added in the future. + </p> + <p>If <c><anno>Result</anno></c> is an integer, it represents + the time in milli-seconds left until the canceled timer would + have expired.</p> + <p> + If <c><anno>Result</anno></c> is <c>false</c>, a + timer corresponding to <c><anno>TimerRef</anno></c> could not + be found. This can be either because the timer had expired, + already had been canceled, or because <c><anno>TimerRef</anno></c> + never corresponded to a timer. Even if the timer had expired, + it does not tell you whether or not the timeout message has + arrived at its destination yet. + </p> + <note> + <p> + The timer service that manages the timer may be co-located + with another scheduler than the scheduler that the calling + process is executing on. If this is the case, communication + with the timer service takes much longer time than if it + is located locally. If the calling process is in critical + path, and can do other things while waiting for the result + of this operation, or is not interested in the result of + the operation, you want to use option <c>{async, true}</c>. + If using option <c>{async, false}</c>, the calling + process blocks until the operation has been performed. + </p> + </note> <p>See also - <seealso marker="#send_after/3">erlang:send_after/3</seealso>, - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>, + <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>, + <seealso marker="#start_timer/4"><c>erlang:start_timer/4</c></seealso>, and - <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p> - <p>Note: Cancelling a timer does not guarantee that the message - has not already been delivered to the message queue.</p> + <seealso marker="#read_timer/2"><c>erlang:read_timer/2</c></seealso>.</p> + </desc> + </func> + <func> + <name name="cancel_timer" arity="1"/> + <fsummary>Cancels a timer.</fsummary> + <desc> + <p>Cancels a timer. The same as calling + <seealso marker="#cancel_timer/2"><c>erlang:cancel_timer(TimerRef, + [])</c></seealso>.</p> </desc> </func> - <func> <name name="check_old_code" arity="1"/> - <fsummary>Check if a module has old code</fsummary> + <fsummary>Checks if a module has old code.</fsummary> <desc> - <p>Returns <c>true</c> if the <c><anno>Module</anno></c> has old code, - and <c>false</c> otherwise.</p> + <p>Returns <c>true</c> if <c><anno>Module</anno></c> has old code, + otherwise <c>false</c>.</p> <p>See also <seealso marker="kernel:code">code(3)</seealso>.</p> </desc> </func> + <func> <name name="check_process_code" arity="2"/> - <fsummary>Check if a process is executing old code for a module</fsummary> - <desc> - <p>Returns <c>true</c> if the process <c><anno>Pid</anno></c> is executing - old code for <c><anno>Module</anno></c>. That is, if the current call of - the process executes old code for this module, or if the - process has references to old code for this module, or if the - process contains funs that references old code for this - module. Otherwise, it returns <c>false</c>.</p> - <pre> -> <input>check_process_code(Pid, lists).</input> -false</pre> + <fsummary>Checks if a process executes old code for a module.</fsummary> + <desc> + <p>The same as + <seealso marker="#check_process_code/3"><c>erlang:check_process_code(<anno>Pid</anno>, <anno>Module</anno>, [])</c></seealso>.</p> + </desc> + </func> + + <func> + <name name="check_process_code" arity="3"/> + <fsummary>Checks if a process executes old code for a module.</fsummary> + <desc> + <p>Checks if the node local process identified by <c><anno>Pid</anno></c> + executes old code for <c><anno>Module</anno></c>.</p> + <p>The available <c><anno>Option</anno></c>s are as follows:</p> + <taglist> + <tag><c>{allow_gc, boolean()}</c></tag> + <item> + <p>Determines if garbage collection is allowed when performing + the operation. If <c>{allow_gc, false}</c> is passed, and + a garbage collection is needed to determine the + result of the operation, the operation is aborted (see + information on <c><anno>CheckResult</anno></c> in the following). + The default is to allow garbage collection, that is, + <c>{allow_gc, true}</c>.</p> + </item> + <tag><c>{async, RequestId}</c></tag> + <item> + <p>The function <c>check_process_code/3</c> returns + the value <c>async</c> immediately after the request + has been sent. When the request has been processed, the + process that called this function is passed a + message on the form + <c>{check_process_code, <anno>RequestId</anno>, <anno>CheckResult</anno>}</c>.</p> + </item> + </taglist> + <p>If <c><anno>Pid</anno></c> equals <c>self()</c>, and + no <c>async</c> option has been passed, the operation + is performed at once. Otherwise a request for + the operation is sent to the process identified by + <c><anno>Pid</anno></c>, and is handled when + appropriate. If no <c>async</c> option has been passed, + the caller blocks until <c><anno>CheckResult</anno></c> + is available and can be returned.</p> + <p><c><anno>CheckResult</anno></c> informs about the result of + the request as follows:</p> + <taglist> + <tag><c>true</c></tag> + <item> + <p>The process identified by <c><anno>Pid</anno></c> + executes old code for <c><anno>Module</anno></c>. + That is, the current call of the process executes old + code for this module, or the process has references + to old code for this module, or the process contains + funs that references old code for this module.</p> + </item> + <tag><c>false</c></tag> + <item> + <p>The process identified by <c><anno>Pid</anno></c> does + not execute old code for <c><anno>Module</anno></c>.</p> + </item> + <tag><c>aborted</c></tag> + <item> + <p>The operation was aborted, as the process needed to + be garbage collected to determine the operation result, + and the operation was requested + by passing option <c>{allow_gc, false}</c>.</p></item> + </taglist> <p>See also <seealso marker="kernel:code">code(3)</seealso>.</p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item>If <c><anno>Pid</anno></c> is not a node local process identifier. + </item> + <tag><c>badarg</c></tag> + <item>If <c><anno>Module</anno></c> is not an atom. + </item> + <tag><c>badarg</c></tag> + <item>If <c><anno>OptionList</anno></c> is an invalid list of options. + </item> + </taglist> + </desc> + </func> + + <func> + <name name="convert_time_unit" arity="3"/> + <fsummary>Converts time unit of a time value.</fsummary> + <desc> + <p>Converts the <c><anno>Time</anno></c> value of time unit + <c><anno>FromUnit</anno></c> to the corresponding + <c><anno>ConvertedTime</anno></c> value of time unit + <c><anno>ToUnit</anno></c>. The result is rounded + using the floor function.</p> + + <warning><p>You may lose accuracy and precision when converting + between time units. In order to minimize such loss, collect all + data at <c>native</c> time unit and do the conversion on the end + result.</p></warning> </desc> </func> <func> <name name="crc32" arity="1"/> - <fsummary>Compute crc32 (IEEE 802.3) checksum</fsummary> + <fsummary>Computes crc32 (IEEE 802.3) checksum.</fsummary> <desc> - <p>Computes and returns the crc32 (IEEE 802.3 style) checksum for <c><anno>Data</anno></c>.</p> + <p>Computes and returns the crc32 (IEEE 802.3 style) checksum + for <c><anno>Data</anno></c>.</p> </desc> </func> + <func> <name name="crc32" arity="2"/> - <fsummary>Compute crc32 (IEEE 802.3) checksum</fsummary> + <fsummary>Computes crc32 (IEEE 802.3) checksum.</fsummary> <desc> - <p>Continue computing the crc32 checksum by combining - the previous checksum, <c><anno>OldCrc</anno></c>, with the checksum of - <c><anno>Data</anno></c>.</p> - <p>The following code:</p> - <code> - X = erlang:crc32(Data1), - Y = erlang:crc32(X,Data2). - </code> - <p>- would assign the same value to <c>Y</c> as this would:</p> - <code> - Y = erlang:crc32([Data1,Data2]). - </code> + <p>Continues computing the crc32 checksum by combining + the previous checksum, <c><anno>OldCrc</anno></c>, with the checksum of + <c><anno>Data</anno></c>.</p> + <p>The following code:</p> + <code> + X = erlang:crc32(Data1), + Y = erlang:crc32(X,Data2).</code> + <p>assigns the same value to <c>Y</c> as this:</p> + <code> + Y = erlang:crc32([Data1,Data2]).</code> </desc> </func> + <func> <name name="crc32_combine" arity="3"/> - <fsummary>Combine two crc32 (IEEE 802.3) checksums</fsummary> - <desc> - <p>Combines two previously computed crc32 checksums. - This computation requires the size of the data object for - the second checksum to be known.</p> - <p>The following code:</p> + <fsummary>Combines two crc32 (IEEE 802.3) checksums.</fsummary> + <desc> + <p>Combines two previously computed crc32 checksums. + This computation requires the size of the data object for + the second checksum to be known.</p> + <p>The following code:</p> + <code> + Y = erlang:crc32(Data1), + Z = erlang:crc32(Y,Data2).</code> + <p>assigns the same value to <c>Z</c> as this:</p> <code> - Y = erlang:crc32(Data1), - Z = erlang:crc32(Y,Data2). - </code> - <p>- would assign the same value to <c>Z</c> as this would:</p> - <code> - X = erlang:crc32(Data1), - Y = erlang:crc32(Data2), - Z = erlang:crc32_combine(X,Y,iolist_size(Data2)). - </code> + X = erlang:crc32(Data1), + Y = erlang:crc32(Data2), + Z = erlang:crc32_combine(X,Y,iolist_size(Data2)).</code> </desc> </func> + <func> <name name="date" arity="0"/> - <fsummary>Current date</fsummary> + <fsummary>Current date.</fsummary> <desc> <p>Returns the current date as <c>{Year, Month, Day}</c>.</p> - <p>The time zone and daylight saving time correction depend on + <p>The time zone and Daylight Saving Time correction depend on the underlying OS.</p> + <p>Example:</p> <pre> > <input>date().</input> {1995,2,19}</pre> </desc> </func> + <func> <name name="decode_packet" arity="3"/> - <fsummary>Extracts a protocol packet from a binary</fsummary> + <fsummary>Extracts a protocol packet from a binary.</fsummary> <desc> - <p>Decodes the binary <c><anno>Bin</anno></c> according to the packet - protocol specified by <c><anno>Type</anno></c>. Very similar to the packet - handling done by sockets with the option {packet,<anno>Type</anno>}.</p> - <p>If an entire packet is contained in <c><anno>Bin</anno></c> it is + protocol specified by <c><anno>Type</anno></c>. Similar to the packet + handling done by sockets with option {packet,<anno>Type</anno>}.</p> + <p>If an entire packet is contained in <c><anno>Bin</anno></c>, it is returned together with the remainder of the binary as <c>{ok,<anno>Packet</anno>,<anno>Rest</anno>}</c>.</p> <p>If <c><anno>Bin</anno></c> does not contain the entire packet, - <c>{more,<anno>Length</anno>}</c> is returned. <c><anno>Length</anno></c> is either the - expected <em>total size</em> of the packet or <c>undefined</c> - if the expected packet size is not known. <c>decode_packet</c> + <c>{more,<anno>Length</anno>}</c> is returned. + <c><anno>Length</anno></c> is either the + expected <em>total size</em> of the packet, or <c>undefined</c> + if the expected packet size is unknown. <c>decode_packet</c> can then be called again with more data added.</p> - <p>If the packet does not conform to the protocol format + <p>If the packet does not conform to the protocol format, <c>{error,<anno>Reason</anno>}</c> is returned.</p> - <p>The following values of <c><anno>Type</anno></c> are valid:</p> + <p>The following <c>Type</c>s are valid:</p> <taglist> <tag><c>raw | 0</c></tag> <item> - <p>No packet handling is done. Entire binary is + <p>No packet handling is done. The entire binary is returned unless it is empty.</p> </item> <tag><c>1 | 2 | 4</c></tag> <item> <p>Packets consist of a header specifying the number of bytes in the packet, followed by that number of bytes. - The length of header can be one, two, or four bytes; + The length of the header can be one, two, or four bytes; the order of the bytes is big-endian. The header - will be stripped off when the packet is returned.</p> + is stripped off when the packet is returned.</p> </item> <tag><c>line</c></tag> <item> - <p>A packet is a line terminated with newline. The - newline character is included in the returned packet - unless the line was truncated according to the option - <c>line_length</c>.</p> + <p>A packet is a line terminated by a delimiter byte, + default is the latin1 newline character. The delimiter + byte is included in the returned packet unless the line + was truncated according to option <c>line_length</c>.</p> </item> <tag><c>asn1 | cdr | sunrm | fcgi | tpkt</c></tag> <item> @@ -626,41 +895,50 @@ false</pre> <item> <p>The Hypertext Transfer Protocol. The packets are returned with the format according to - <c><anno>HttpPacket</anno></c> described above. A packet is either a - request, a response, a header or an end of header - mark. Invalid lines are returned as <c><anno>HttpError</anno></c>.</p> - <p>Recognized request methods and header fields are returned as atoms. - Others are returned as strings. Strings of unrecognized header fields - are formatted with only capital letters first and after hyphen characters - (like <c>"Sec-Websocket-Key"</c>).</p> - <p>The protocol type <c>http</c> should only be used for - the first line when a <c><anno>HttpRequest</anno></c> or a - <c><anno>HttpResponse</anno></c> is expected. The following calls - should use <c>httph</c> to get <c><anno>HttpHeader</anno></c>'s until - <c>http_eoh</c> is returned that marks the end of the + <c><anno>HttpPacket</anno></c> described earlier. + A packet is either a + request, a response, a header, or an end of header + mark. Invalid lines are returned as + <c><anno>HttpError</anno></c>.</p> + <p>Recognized request methods and header fields are returned + as atoms. Others are returned as strings. Strings of + unrecognized header fields are formatted with only + capital letters first and after hyphen characters, for + example, <c>"Sec-Websocket-Key"</c>.</p> + <p>The protocol type <c>http</c> is only to be used for + the first line when an <c><anno>HttpRequest</anno></c> or an + <c><anno>HttpResponse</anno></c> is expected. + The following calls are to use <c>httph</c> to get + <c><anno>HttpHeader</anno></c>s until + <c>http_eoh</c> is returned, which marks the end of the headers and the beginning of any following message body.</p> - <p>The variants <c>http_bin</c> and <c>httph_bin</c> will return + <p>The variants <c>http_bin</c> and <c>httph_bin</c> return strings (<c>HttpString</c>) as binaries instead of lists.</p> </item> </taglist> <p>The following options are available:</p> <taglist> <tag><c>{packet_size, integer() >= 0}</c></tag> - <item><p>Sets the max allowed size of the packet body. If - the packet header indicates that the length of the - packet is longer than the max allowed length, the packet - is considered invalid. Default is 0 which means no - size limit.</p> + <item><p>Sets the maximum allowed size of the packet body. + If the packet header indicates that the length of the + packet is longer than the maximum allowed length, the + packet is considered invalid. Default is 0, which means + no size limit.</p> </item> <tag><c>{line_length, integer() >= 0}</c></tag> - <item><p>For packet type <c>line</c>, truncate lines longer - than the indicated length.</p> - <p>Option <c>line_length</c> also applies to <c>http*</c> - packet types as an alias for option <c>packet_size</c> in the - case when <c>packet_size</c> itself is not set. This usage is - only intended for backward compatibility.</p> + <item><p>For packet type <c>line</c>, lines longer than + the indicated length are truncated.</p> + <p>Option <c>line_length</c> also applies to <c>http*</c> + packet types as an alias for option <c>packet_size</c> + if <c>packet_size</c> itself is not set. This use is + only intended for backward compatibility.</p> + </item> + <tag><c>{line_delimiter, 0 =< byte() =< 255}</c></tag> + <item><p>For packet type <c>line</c>, sets the delimiting byte. + Default is the latin1 character <c>$\n</c>.</p> </item> </taglist> + <p>Examples:</p> <pre> > <input>erlang:decode_packet(1,<<3,"abcd">>,[]).</input> {ok,<<"abc">>,<<"d">>} @@ -671,13 +949,11 @@ false</pre> <func> <name name="delete_element" arity="2"/> - <fsummary>Delete element at index in a tuple</fsummary> + <fsummary>Deletes element at index in a tuple.</fsummary> <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno>)</type_desc> <desc> - <p> - Returns a new tuple with element at <c><anno>Index</anno></c> removed from - tuple <c><anno>Tuple1</anno></c>. - </p> + <p>Returns a new tuple with element at <c><anno>Index</anno></c> + removed from tuple <c><anno>Tuple1</anno></c>, for example:</p> <pre> > <input>erlang:delete_element(2, {one, two, three}).</input> {one,three}</pre> @@ -686,45 +962,49 @@ false</pre> <func> <name name="delete_module" arity="1"/> - <fsummary>Make the current code for a module old</fsummary> + <fsummary>Makes the current code for a module old.</fsummary> <desc> - <p>Makes the current code for <c><anno>Module</anno></c> become old code, and - deletes all references for this module from the export table. + <p>Makes the current code for <c><anno>Module</anno></c> become old code, + and deletes all references for this module from the export table. Returns <c>undefined</c> if the module does not exist, otherwise <c>true</c>.</p> <warning> <p>This BIF is intended for the code server (see - <seealso marker="kernel:code">code(3)</seealso>) and should not be - used elsewhere.</p> + <seealso marker="kernel:code">code(3)</seealso>) and is not + to be used elsewhere.</p> </warning> - <p>Failure: <c>badarg</c> if there is already an old version of + <p>Failure: <c>badarg</c> if there already is an old version of <c>Module</c>.</p> </desc> </func> + <func> <name name="demonitor" arity="1"/> - <fsummary>Stop monitoring</fsummary> + <fsummary>Stops monitoring.</fsummary> <desc> - <p>If <c><anno>MonitorRef</anno></c> is a reference which the calling process - obtained by calling + <p>If <c><anno>MonitorRef</anno></c> is a reference that the + calling process obtained by calling <seealso marker="#monitor/2">monitor/2</seealso>, this monitoring is turned off. If the monitoring is already turned off, nothing happens.</p> - <p>Once <c>demonitor(<anno>MonitorRef</anno>)</c> has returned it is - guaranteed that no <c>{'DOWN', <anno>MonitorRef</anno>, _, _, _}</c> message - due to the monitor will be placed in the caller's message queue - in the future. A <c>{'DOWN', <anno>MonitorRef</anno>, _, _, _}</c> message - might have been placed in the caller's message queue prior to - the call, though. Therefore, in most cases, it is advisable + <p>Once <c>demonitor(<anno>MonitorRef</anno>)</c> has returned, it is + guaranteed that no <c>{'DOWN', + <anno>MonitorRef</anno>, _, _, _}</c> message, + because of the monitor, will be placed in the caller message queue + in the future. A <c>{'DOWN', + <anno>MonitorRef</anno>, _, _, _}</c> message + can have been placed in the caller message queue before + the call, though. It is therefore usually advisable to remove such a <c>'DOWN'</c> message from the message queue - after monitoring has been stopped. - <seealso marker="#demonitor/2">demonitor(<anno>MonitorRef</anno>, [flush])</seealso> can be used instead of + after monitoring has been stopped. + <seealso marker="#demonitor/2"><c>demonitor(<anno>MonitorRef</anno>, [flush])</c></seealso> + can be used instead of <c>demonitor(<anno>MonitorRef</anno>)</c> if this cleanup is wanted.</p> <note> - <p>Prior to OTP release R11B (erts version 5.5) <c>demonitor/1</c> - behaved completely asynchronous, i.e., the monitor was active + <p>Prior to OTP release R11B (ERTS version 5.5) <c>demonitor/1</c> + behaved completely asynchronously, i.e., the monitor was active until the "demonitor signal" reached the monitored entity. This - had one undesirable effect, though. You could never know when + had one undesirable effect. You could never know when you were guaranteed <em>not</em> to receive a <c>DOWN</c> message due to the monitor.</p> <p>Current behavior can be viewed as two combined operations: @@ -733,31 +1013,31 @@ false</pre> </note> <p>Failure: It is an error if <c><anno>MonitorRef</anno></c> refers to a monitoring started by another process. Not all such cases are - cheap to check; if checking is cheap, the call fails with - <c>badarg</c> (for example if <c><anno>MonitorRef</anno></c> is a remote - reference).</p> + cheap to check. If checking is cheap, the call fails with + <c>badarg</c> for example, if <c><anno>MonitorRef</anno></c> is a + remote reference.</p> </desc> </func> + <func> <name name="demonitor" arity="2"/> - <fsummary>Stop monitoring</fsummary> + <fsummary>Stops monitoring.</fsummary> <desc> <p>The returned value is <c>true</c> unless <c>info</c> is part - of <c><anno>OptionList</anno></c>. - </p> + of <c><anno>OptionList</anno></c>.</p> <p><c>demonitor(<anno>MonitorRef</anno>, [])</c> is equivalent to - <seealso marker="#demonitor/1">demonitor(<anno>MonitorRef</anno>)</seealso>.</p> - <p>Currently the following <c><anno>Option</anno></c>s are valid:</p> + <seealso marker="#demonitor/1"><c>demonitor(<anno>MonitorRef</anno>)</c></seealso>.</p> + <p>The available <c><anno>Option</anno></c>s are as follows:</p> <taglist> <tag><c>flush</c></tag> <item> - <p>Remove (one) <c>{_, <anno>MonitorRef</anno>, _, _, _}</c> message, - if there is one, from the caller's message queue after + <p>Removes (one) <c>{_, + <anno>MonitorRef</anno>, _, _, _}</c> message, + if there is one, from the caller message queue after monitoring has been stopped.</p> <p>Calling <c>demonitor(<anno>MonitorRef</anno>, [flush])</c> is equivalent to the following, but more efficient:</p> <code type="none"> - demonitor(MonitorRef), receive {_, MonitorRef, _, _, _} -> @@ -768,78 +1048,90 @@ false</pre> </item> <tag><c>info</c></tag> <item> - <p>The returned value is one of the following:</p> - <taglist> - <tag><c>true</c></tag> - <item><p>The monitor was found and removed. In this case - no <c>'DOWN'</c> message due to this monitor have - been nor will be placed in the message queue - of the caller. - </p> - </item> - <tag><c>false</c></tag> - <item><p>The monitor was not found and could not be removed. - This probably because someone already has placed a - <c>'DOWN'</c> message corresponding to this monitor - in the caller's message queue. - </p> - </item> - </taglist> - <p>If the <c>info</c> option is combined with the <c>flush</c> - option, <c>false</c> will be returned if a flush was needed; - otherwise, <c>true</c>. - </p> + <p>The returned value is one of the following:</p> + <taglist> + <tag><c>true</c></tag> + <item>The monitor was found and removed. In this case, + no <c>'DOWN'</c> message corresponding to this + monitor has been delivered and will not be delivered. + </item> + <tag><c>false</c></tag> + <item>The monitor was not found and could not be removed. + This probably because someone already has placed a + <c>'DOWN'</c> message corresponding to this monitor + in the caller message queue. + </item> + </taglist> + <p>If option <c>info</c> is combined with option <c>flush</c>, + <c>false</c> is returned if a flush was needed, + otherwise <c>true</c>.</p> </item> </taglist> <note> - <p>More options may be added in the future.</p> + <p>More options can be added in a future release.</p> </note> - <p>Failure: <c>badarg</c> if <c><anno>OptionList</anno></c> is not a list, or - if <c><anno>Option</anno></c> is not a valid option, or the same failure as for - <seealso marker="#demonitor/1">demonitor/1</seealso></p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item>If <c><anno>OptionList</anno></c> is not a list. + </item> + <tag><c>badarg</c></tag> + <item>If <c><anno>Option</anno></c> is an invalid option. + </item> + <tag><c>badarg</c></tag> + <item>The same failure as for + <seealso marker="#demonitor/1">demonitor/1</seealso>. + </item> + </taglist> </desc> </func> + <func> <name name="disconnect_node" arity="1"/> - <fsummary>Force the disconnection of a node</fsummary> + <fsummary>Forces the disconnection of a node.</fsummary> <desc> - <p>Forces the disconnection of a node. This will appear to - the node <c><anno>Node</anno></c> as if the local node has crashed. This - BIF is mainly used in the Erlang network authentication - protocols. Returns <c>true</c> if disconnection succeeds, + <p>Forces the disconnection of a node. This appears to + the node <c><anno>Node</anno></c> as if the local node has crashed. + This BIF is mainly used in the Erlang network authentication + protocols.</p> + <p>Returns <c>true</c> if disconnection succeeds, otherwise <c>false</c>. If the local node is not alive, - the function returns <c>ignored</c>.</p> + <c>ignored</c> is returned.</p> </desc> </func> + <func> <name name="display" arity="1"/> - <fsummary>Print a term on standard output</fsummary> + <fsummary>Prints a term on standard output.</fsummary> <desc> - <p>Prints a text representation of <c><anno>Term</anno></c> on the standard - output.</p> + <p>Prints a text representation of <c><anno>Term</anno></c> on the + standard output. On OSE, the term is printed to the ramlog.</p> <warning> <p>This BIF is intended for debugging only.</p> </warning> </desc> </func> + <func> <name name="element" arity="2"/> + <fsummary>Returns the Nth element of a tuple.</fsummary> <type_desc variable="N">1..tuple_size(<anno>Tuple</anno>)</type_desc> - <fsummary>Get Nth element of a tuple</fsummary> <desc> <p>Returns the <c><anno>N</anno></c>th element (numbering from 1) of - <c><anno>Tuple</anno></c>.</p> + <c><anno>Tuple</anno></c>, for example:</p> <pre> > <input>element(2, {a, b, c}).</input> b</pre> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="erase" arity="0"/> - <fsummary>Return and delete the process dictionary</fsummary> + <fsummary>Returns and deletes the process dictionary.</fsummary> <desc> - <p>Returns the process dictionary and deletes it.</p> + <p>Returns the process dictionary and deletes it, for + example:</p> <pre> > <input>put(key1, {1, 2, 3}),</input> <input>put(key2, [a, b, c]),</input> @@ -847,13 +1139,16 @@ b</pre> [{key1,{1,2,3}},{key2,[a,b,c]}]</pre> </desc> </func> + <func> <name name="erase" arity="1"/> - <fsummary>Return and delete a value from the process dictionary</fsummary> + <fsummary>Returns and deletes a value from the process dictionary.</fsummary> <desc> - <p>Returns the value <c><anno>Val</anno></c> associated with <c><anno>Key</anno></c> and - deletes it from the process dictionary. Returns - <c>undefined</c> if no value is associated with <c><anno>Key</anno></c>.</p> + <p>Returns the value <c><anno>Val</anno></c> associated with + <c><anno>Key</anno></c> and deletes it from the process dictionary. + Returns <c>undefined</c> if no value is associated with + <c><anno>Key</anno></c>.</p> + <p>Example:</p> <pre> > <input>put(key1, {merry, lambs, are, playing}),</input> <input>X = erase(key1),</input> @@ -861,16 +1156,19 @@ b</pre> {{merry,lambs,are,playing},undefined}</pre> </desc> </func> + <func> <name name="error" arity="1"/> - <fsummary>Stop execution with a given reason</fsummary> + <fsummary>Stops execution with a given reason.</fsummary> <desc> <p>Stops the execution of the calling process with the reason - <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> is any term. The actual - exit reason will be <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c> + <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> + is any term. The exit reason is + <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c> is a list of the functions most recently called (the current function first). Since evaluating this function causes the process to terminate, it has no return value.</p> + <p>Example:</p> <pre> > <input>catch error(foobar).</input> {'EXIT',{foobar,[{erl_eval,do_apply,5}, @@ -880,29 +1178,34 @@ b</pre> {shell,eval_loop,3}]}}</pre> </desc> </func> + <func> <name name="error" arity="2"/> - <fsummary>Stop execution with a given reason</fsummary> + <fsummary>Stops execution with a given reason.</fsummary> <desc> <p>Stops the execution of the calling process with the reason - <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> is any term. The actual - exit reason will be <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c> + <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> + is any term. The exit reason is + <c>{<anno>Reason</anno>, Where}</c>, where <c>Where</c> is a list of the functions most recently called (the current - function first). <c><anno>Args</anno></c> is expected to be the list of - arguments for the current function; in Beam it will be used - to provide the actual arguments for the current function in - the <c>Where</c> term. Since evaluating this function causes + function first). <c><anno>Args</anno></c> is expected to be the + list of arguments for the current function; in Beam it is used + to provide the arguments for the current function in + the term <c>Where</c>. Since evaluating this function causes the process to terminate, it has no return value.</p> </desc> </func> + <func> <name name="exit" arity="1"/> - <fsummary>Stop execution with a given reason</fsummary> + <fsummary>Stops execution with a given reason.</fsummary> <desc> - <p>Stops the execution of the calling process with the exit - reason <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> is any term. Since + <p>Stops the execution of the calling process with exit reason + <c><anno>Reason</anno></c>, where <c><anno>Reason</anno></c> + is any term. Since evaluating this function causes the process to terminate, it has no return value.</p> + <p>Example:</p> <pre> > <input>exit(foobar).</input> ** exception exit: foobar @@ -910,110 +1213,117 @@ b</pre> {'EXIT',foobar}</pre> </desc> </func> + <func> <name name="exit" arity="2"/> - <fsummary>Send an exit signal to a process or a port</fsummary> + <fsummary>Sends an exit signal to a process or a port.</fsummary> <desc> <p>Sends an exit signal with exit reason <c><anno>Reason</anno></c> to the process or port identified by <c><anno>Pid</anno></c>.</p> - <p>The following behavior apply if <c><anno>Reason</anno></c> is any term - except <c>normal</c> or <c>kill</c>:</p> - <p>If <c><anno>Pid</anno></c> is not trapping exits, <c><anno>Pid</anno></c> itself will - exit with exit reason <c><anno>Reason</anno></c>. If <c><anno>Pid</anno></c> is trapping - exits, the exit signal is transformed into a message - <c>{'EXIT', From, <anno>Reason</anno>}</c> and delivered to the message - queue of <c><anno>Pid</anno></c>. <c>From</c> is the pid of the process - which sent the exit signal. See also - <seealso marker="#process_flag/2">process_flag/2</seealso>.</p> - <p>If <c><anno>Reason</anno></c> is the atom <c>normal</c>, <c><anno>Pid</anno></c> will - not exit. If it is trapping exits, the exit signal is - transformed into a message <c>{'EXIT', From, normal}</c> - and delivered to its message queue.</p> - <p>If <c><anno>Reason</anno></c> is the atom <c>kill</c>, that is if - <c>exit(<anno>Pid</anno>, kill)</c> is called, an untrappable exit signal - is sent to <c><anno>Pid</anno></c> which will unconditionally exit with - exit reason <c>killed</c>.</p> + <p>The following behavior applies if <c><anno>Reason</anno></c> + is any term, except <c>normal</c> or <c>kill</c>:</p> + <list type="bulleted"> + <item>If <c><anno>Pid</anno></c> is not trapping exits, + <c><anno>Pid</anno></c> + itself exits with exit reason <c><anno>Reason</anno></c>. + </item> + <item>If <c><anno>Pid</anno></c> is trapping exits, the exit + signal is transformed into a message + <c>{'EXIT', From, <anno>Reason</anno>}</c> + and delivered to the message queue of <c><anno>Pid</anno></c>. + </item> + <item><c>From</c> is the process identifier of the process + that sent the exit signal. See also + <seealso marker="#process_flag/2">process_flag/2</seealso>. + </item> + </list> + <p>If <c><anno>Reason</anno></c> is the atom <c>normal</c>, + <c><anno>Pid</anno></c> + does not exit. If it is trapping exits, the exit signal is + transformed into a message <c>{'EXIT', From, normal}</c> + and delivered to its message queue.</p> + <p>If <c><anno>Reason</anno></c> is the atom <c>kill</c>, + that is, if <c>exit(<anno>Pid</anno>, kill)</c> is called, + an untrappable exit signal is sent to <c><anno>Pid</anno></c>, + which unconditionally exits with exit reason <c>killed</c>. + </p> </desc> </func> + <func> <name name="external_size" arity="1"/> - <fsummary>Calculate the maximum size for a term encoded in the Erlang - external term format</fsummary> + <fsummary>Calculates the maximum size for a term encoded in the Erlang external term format.</fsummary> <desc> <p>Calculates, without doing the encoding, the maximum byte size for a term encoded in the Erlang external term format. The following condition applies always:</p> - <p> <pre> > <input>Size1 = byte_size(term_to_binary(<anno>Term</anno>)),</input> > <input>Size2 = erlang:external_size(<anno>Term</anno>),</input> > <input>true = Size1 =< Size2.</input> -true - </pre> - </p> - <p>This is equivalent to a call to: <code>erlang:external_size(<anno>Term</anno>, []) - </code></p> +true</pre> + <p>This is equivalent to a call to:</p> +<code>erlang:external_size(<anno>Term</anno>, [])</code> </desc> </func> + <func> <name name="external_size" arity="2"/> - <fsummary>Calculate the maximum size for a term encoded in the Erlang - external term format</fsummary> + <fsummary>Calculates the maximum size for a term encoded in the Erlang external term format.</fsummary> <desc> <p>Calculates, without doing the encoding, the maximum byte size for a term encoded in the Erlang external term format. The following condition applies always:</p> - <p> <pre> > <input>Size1 = byte_size(term_to_binary(<anno>Term</anno>, <anno>Options</anno>)),</input> > <input>Size2 = erlang:external_size(<anno>Term</anno>, <anno>Options</anno>),</input> > <input>true = Size1 =< Size2.</input> -true - </pre> - </p> - <p>The option <c>{minor_version, <anno>Version</anno>}</c> specifies how floats - are encoded. See - <seealso marker="#term_to_binary/2">term_to_binary/2</seealso> for - a more detailed description. - </p> +true</pre> + <p>Option <c>{minor_version, <anno>Version</anno>}</c> specifies how + floats are encoded. For a detailed description, see + <seealso marker="#term_to_binary/2">term_to_binary/2</seealso>.</p> </desc> </func> + <func> <name name="float" arity="1"/> - <fsummary>Convert a number to a float</fsummary> + <fsummary>Converts a number to a float.</fsummary> <desc> - <p>Returns a float by converting <c><anno>Number</anno></c> to a float.</p> + <p>Returns a float by converting <c><anno>Number</anno></c> to a float, + for example:</p> <pre> > <input>float(55).</input> 55.0</pre> <p>Allowed in guard tests.</p> <note> - <p>Note that if used on the top-level in a guard, it will - test whether the argument is a floating point number; for - clarity, use + <p>If used on the top level in a guard, it tests whether the + argument is a floating point number; for clarity, use <seealso marker="#is_float/1">is_float/1</seealso> instead.</p> <p>When <c>float/1</c> is used in an expression in a guard, such as '<c>float(A) == 4.0</c>', it converts a number as - described above.</p> + described earlier.</p> </note> </desc> </func> + <func> <name name="float_to_binary" arity="1"/> - <fsummary>Text representation of a float</fsummary> + <fsummary>Text representation of a float.</fsummary> <desc> - <p>The same as <c>float_to_binary(<anno>Float</anno>,[{scientific,20}])</c>.</p> + <p>The same as + <c>float_to_binary(<anno>Float</anno>,[{scientific,20}])</c>.</p> </desc> </func> + <func> <name name="float_to_binary" arity="2"/> - <fsummary>Text representation of a float formatted using given options</fsummary> + <fsummary>Text representation of a float formatted using given options.</fsummary> <desc> - <p>Returns a binary which corresponds to the text + <p>Returns a binary corresponding to the text representation of <c><anno>Float</anno></c> using fixed decimal - point formatting. The <c><anno>Options</anno></c> behave in the same - way as <seealso marker="#float_to_list/2">float_to_list/2</seealso>. - </p> + point formatting. <c><anno>Options</anno></c> behaves in the same + way as <seealso marker="#float_to_list/2">float_to_list/2</seealso>.</p> + <p>Examples:</p> <pre> > <input>float_to_binary(7.12, [{decimals, 4}]).</input> <<"7.1200">> @@ -1021,31 +1331,42 @@ true <<"7.12">></pre> </desc> </func> + <func> <name name="float_to_list" arity="1"/> - <fsummary>Text representation of a float</fsummary> + <fsummary>Text representation of a float.</fsummary> <desc> - <p>The same as <c>float_to_list(<anno>Float</anno>,[{scientific,20}])</c>.</p> + <p>The same as + <c>float_to_list(<anno>Float</anno>,[{scientific,20}])</c>.</p> </desc> </func> + <func> <name name="float_to_list" arity="2"/> - <fsummary>Text representation of a float formatted using given options</fsummary> - <desc> - <p>Returns a string which corresponds to the text - representation of <c>Float</c> using fixed decimal point formatting. - When <c>decimals</c> option is specified - the returned value will contain at most <c>Decimals</c> number of - digits past the decimal point. If the number doesn't fit in the - internal static buffer of 256 bytes, the function throws <c>badarg</c>. - When <c>compact</c> option is provided - the trailing zeros at the end of the list are truncated (this option is - only meaningful together with the <c>decimals</c> option). When - <c>scientific</c> option is provided, the float will be formatted using - scientific notation with <c>Decimals</c> digits of precision. If - <c>Options</c> is <c>[]</c> the function behaves like - <c><seealso marker="#float_to_list/1">float_to_list/1</seealso></c>. - </p> + <fsummary>Text representation of a float formatted using given options.</fsummary> + <desc> + <p>Returns a string corresponding to the text representation + of <c>Float</c> using fixed decimal point formatting. The + options are as follows:</p> + <list type="bulleted"> + <item>If option <c>decimals</c> is specified, the returned value + contains at most <c>Decimals</c> number of digits past the + decimal point. If the number does not fit in the internal + static buffer of 256 bytes, the function throws <c>badarg</c>. + </item> + <item>If option <c>compact</c> is provided, the trailing zeros + at the end of the list are truncated. This option is only + meaningful together with option <c>decimals</c>. + </item> + <item>If option <c>scientific</c> is provided, the float is + formatted using scientific notation with <c>Decimals</c> + digits of precision. + </item> + <item>If <c>Options</c> is <c>[]</c>, the function behaves as + <seealso marker="#float_to_list/1">float_to_list/1</seealso>. + </item> + </list> + <p>Examples:</p> <pre> > <input>float_to_list(7.12, [{decimals, 4}]).</input> "7.1200" @@ -1053,36 +1374,40 @@ true "7.12"</pre> </desc> </func> + <func> <name name="fun_info" arity="1"/> - <fsummary>Information about a fun</fsummary> + <fsummary>Information about a fun.</fsummary> <desc> - <p>Returns a list containing information about the fun - <c><anno>Fun</anno></c>. Each element of the list is a tuple. The order of - the tuples is not defined, and more tuples may be added in a + <p>Returns a list with information about the fun + <c><anno>Fun</anno></c>. Each list element is a tuple. The order + of the tuples is undefined, and more tuples can be added in a future release.</p> <warning> <p>This BIF is mainly intended for debugging, but it can - occasionally be useful in library functions that might need - to verify, for instance, the arity of a fun.</p> + sometimes be useful in library functions that need + to verify, for example, the arity of a fun.</p> </warning> - <p>There are two types of funs with slightly different - semantics:</p> - <p>A fun created by <c>fun M:F/A</c> is called an - <em>external</em> fun. Calling it will always call the - function <c>F</c> with arity <c>A</c> in the latest code for - module <c>M</c>. Note that module <c>M</c> does not even need - to be loaded when the fun <c>fun M:F/A</c> is created.</p> - <p>All other funs are called <em>local</em>. When a local fun - is called, the same version of the code that created the fun - will be called (even if newer version of the module has been - loaded).</p> - <p>The following elements will always be present in the list + <p>Two types of funs have slightly different semantics:</p> + <list type="bulleted"> + <item>A fun created by <c>fun M:F/A</c> is called an + <em>external</em> fun. Calling it will always call the + function <c>F</c> with arity <c>A</c> in the latest code for + module <c>M</c>. Notice that module <c>M</c> does not even + need to be loaded when the fun <c>fun M:F/A</c> is created. + </item> + <item>All other funs are called <em>local</em>. When a local fun + is called, the same version of the code that created the fun + is called (even if a newer version of the module has been + loaded). + </item> + </list> + <p>The following elements are always present in the list for both local and external funs:</p> <taglist> <tag><c>{type, Type}</c></tag> <item> - <p><c>Type</c> is either <c>local</c> or <c>external</c>.</p> + <p><c>Type</c> is <c>local</c> or <c>external</c>.</p> </item> <tag><c>{module, Module}</c></tag> <item> @@ -1097,128 +1422,189 @@ true <p><c>Name</c> (an atom) is a function name.</p> <p>If <c>Fun</c> is a local fun, <c>Name</c> is the name of the local function that implements the fun. - (This name was generated by the compiler, and is generally + (This name was generated by the compiler, and is only of informational use. As it is a local function, it - is not possible to call it directly.) + cannot be called directly.) If no code is currently loaded for the fun, <c>[]</c> - will be returned instead of an atom.</p> + is returned instead of an atom.</p> <p>If <c>Fun</c> is an external fun, <c>Name</c> is the name of the exported function that the fun refers to.</p> </item> <tag><c>{arity, Arity}</c></tag> <item> <p><c>Arity</c> is the number of arguments that the fun - should be called with.</p> + is to be called with.</p> </item> <tag><c>{env, Env}</c></tag> <item> <p><c>Env</c> (a list) is the environment or free variables - for the fun. (For external funs, the returned list is - always empty.)</p> + for the fun. For external funs, the returned list is + always empty.</p> </item> </taglist> - <p>The following elements will only be present in the list if + <p>The following elements are only present in the list if <c>Fun</c> is local:</p> <taglist> <tag><c>{pid, Pid}</c></tag> <item> - <p><c>Pid</c> is the pid of the process that originally - created the fun.</p> + <p><c>Pid</c> is the process identifier of the process + that originally created the fun.</p> </item> <tag><c>{index, Index}</c></tag> <item> - <p><c>Index</c> (an integer) is an index into the module's + <p><c>Index</c> (an integer) is an index into the module fun table.</p> </item> <tag><c>{new_index, Index}</c></tag> <item> - <p><c>Index</c> (an integer) is an index into the module's + <p><c>Index</c> (an integer) is an index into the module fun table.</p> </item> <tag><c>{new_uniq, Uniq}</c></tag> <item> - <p><c>Uniq</c> (a binary) is a unique value for this fun. - It is calculated from the compiled code for the entire module.</p> + <p><c>Uniq</c> (a binary) is a unique value for this fun. It + is calculated from the compiled code for the entire module.</p> </item> <tag><c>{uniq, Uniq}</c></tag> <item> <p><c>Uniq</c> (an integer) is a unique value for this fun. - Starting in the R15 release, this integer is calculated from - the compiled code for the entire module. Before R15, this - integer was based on only the body of the fun. - </p> + As from OTP R15, this integer is calculated from the + compiled code for the entire module. Before OTP R15, this + integer was based on only the body of the fun.</p> </item> </taglist> </desc> </func> + <func> <name name="fun_info" arity="2"/> + <fsummary>Information about a fun.</fsummary> <type name="fun_info_item"/> - <fsummary>Information about a fun</fsummary> <desc> <p>Returns information about <c><anno>Fun</anno></c> as specified by - <c><anno>Item</anno></c>, in the form <c>{<anno>Item</anno>,<anno>Info</anno>}</c>.</p> + <c><anno>Item</anno></c>, in the form + <c>{<anno>Item</anno>,<anno>Info</anno>}</c>.</p> <p>For any fun, <c><anno>Item</anno></c> can be any of the atoms - <c>module</c>, <c>name</c>, <c>arity</c>, <c>env</c>, or <c>type</c>.</p> - <p>For a local fun, <c><anno>Item</anno></c> can also be any of the atoms - <c>index</c>, <c>new_index</c>, <c>new_uniq</c>, + <c>module</c>, <c>name</c>, <c>arity</c>, <c>env</c>, or + <c>type</c>.</p> + <p>For a local fun, <c><anno>Item</anno></c> can also be any of the + atoms <c>index</c>, <c>new_index</c>, <c>new_uniq</c>, <c>uniq</c>, and <c>pid</c>. For an external fun, the value of any of these items is always the atom <c>undefined</c>.</p> <p>See <seealso marker="#fun_info/1">erlang:fun_info/1</seealso>.</p> </desc> </func> + <func> <name name="fun_to_list" arity="1"/> - <fsummary>Text representation of a fun</fsummary> + <fsummary>Text representation of a fun.</fsummary> <desc> - <p>Returns a string which corresponds to the text + <p>Returns a string corresponding to the text representation of <c><anno>Fun</anno></c>.</p> </desc> </func> + <func> <name name="function_exported" arity="3"/> - <fsummary>Check if a function is exported and loaded</fsummary> + <fsummary>Checks if a function is exported and loaded.</fsummary> <desc> <p>Returns <c>true</c> if the module <c><anno>Module</anno></c> is loaded - and contains an exported function <c><anno>Function</anno>/<anno>Arity</anno></c>; - otherwise <c>false</c>.</p> - <p>Returns <c>false</c> for any BIF (functions implemented in C - rather than in Erlang).</p> + and contains an exported function <c><anno>Function</anno>/<anno>Arity</anno></c>, + or if there is a BIF (a built-in function implemented in C) + with the given name, otherwise returns <c>false</c>.</p> + <note><p>This function used to return false for built-in + functions before the 18.0 release.</p></note> </desc> </func> + <func> <name name="garbage_collect" arity="0"/> - <fsummary>Force an immediate garbage collection of the calling process</fsummary> + <fsummary>Forces an immediate garbage collection of the calling process.</fsummary> <desc> - <p>Forces an immediate garbage collection of the currently - executing process. The function should not be used, unless - it has been noticed -- or there are good reasons to suspect -- + <p>Forces an immediate garbage collection of the + executing process. The function is not to be used unless + it has been noticed (or there are good reasons to suspect) that the spontaneous garbage collection will occur too late - or not at all. Improper use may seriously degrade system - performance.</p> - <p>Compatibility note: In versions of OTP prior to R7, - the garbage collection took place at the next context switch, - not immediately. To force a context switch after a call to - <c>erlang:garbage_collect()</c>, it was sufficient to make - any function call.</p> + or not at all.</p> + <warning> + <p>Improper use can seriously degrade system performance.</p> + </warning> </desc> </func> + <func> <name name="garbage_collect" arity="1"/> - <fsummary>Force an immediate garbage collection of a process</fsummary> + <fsummary>Garbage collects a process.</fsummary> <desc> - <p>Works like <c>erlang:garbage_collect()</c> but on any - process. The same caveats apply. Returns <c>false</c> if - <c><anno>Pid</anno></c> refers to a dead process; <c>true</c> otherwise.</p> + <p>The same as + <seealso marker="#garbage_collect/2"><c>garbage_collect(<anno>Pid</anno>, [])</c></seealso>.</p> </desc> </func> + + <func> + <name name="garbage_collect" arity="2"/> + <fsummary>Garbage collects a process.</fsummary> + <desc> + <p>Garbage collects the node local process identified by + <c><anno>Pid</anno></c>.</p> + <p>The available <c><anno>Option</anno></c>s are as follows:</p> + <taglist> + <tag><c>{async, RequestId}</c></tag> + <item>The function <c>garbage_collect/2</c> returns + the value <c>async</c> immediately after the request + has been sent. When the request has been processed, the + process that called this function is passed a message on + the form <c>{garbage_collect, + <anno>RequestId</anno>, <anno>GCResult</anno>}</c>. + </item> + </taglist> + <p>If <c><anno>Pid</anno></c> equals <c>self()</c>, and + no <c>async</c> option has been passed, the garbage + collection is performed at once, that is, the same as calling + <seealso marker="#garbage_collect/0">garbage_collect/0</seealso>. + Otherwise a request for garbage collection + is sent to the process identified by <c><anno>Pid</anno></c>, + and will be handled when appropriate. If no <c>async</c> + option has been passed, the caller blocks until + <c><anno>GCResult</anno></c> is available and can be returned.</p> + <p><c><anno>GCResult</anno></c> informs about the result of + the garbage collection request as follows:</p> + <taglist> + <tag><c>true</c></tag> + <item> + The process identified by <c><anno>Pid</anno></c> has + been garbage collected. + </item> + <tag><c>false</c></tag> + <item> + No garbage collection was performed, as + the process identified by <c><anno>Pid</anno></c> + terminated before the request could be satisfied. + </item> + </taglist> + <p>Notice that the same caveats apply as for + <seealso marker="#garbage_collect/0">garbage_collect/0</seealso>.</p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item> + If <c><anno>Pid</anno></c> is not a node local process identifier. + </item> + <tag><c>badarg</c></tag> + <item> + If <c><anno>OptionList</anno></c> is an invalid list of options. + </item> + </taglist> + </desc> + </func> + <func> <name name="get" arity="0"/> - <fsummary>Return the process dictionary</fsummary> + <fsummary>Returns the process dictionary.</fsummary> <desc> <p>Returns the process dictionary as a list of - <c>{<anno>Key</anno>, <anno>Val</anno>}</c> tuples.</p> + <c>{<anno>Key</anno>, <anno>Val</anno>}</c> tuples, for example:</p> <pre> > <input>put(key1, merry),</input> <input>put(key2, lambs),</input> @@ -1227,13 +1613,15 @@ true [{key1,merry},{key2,lambs},{key3,{are,playing}}]</pre> </desc> </func> + <func> <name name="get" arity="1"/> - <fsummary>Return a value from the process dictionary</fsummary> + <fsummary>Returns a value from the process dictionary.</fsummary> <desc> - <p>Returns the value <c><anno>Val</anno></c>associated with <c><anno>Key</anno></c> in + <p>Returns the value <c><anno>Val</anno></c> associated with <c><anno>Key</anno></c> in the process dictionary, or <c>undefined</c> if <c><anno>Key</anno></c> does not exist.</p> + <p>Example:</p> <pre> > <input>put(key1, merry),</input> <input>put(key2, lambs),</input> @@ -1242,20 +1630,35 @@ true {are,playing}</pre> </desc> </func> + <func> <name name="get_cookie" arity="0"/> - <fsummary>Get the magic cookie of the local node</fsummary> + <fsummary>Gets the magic cookie of the local node.</fsummary> <desc> - <p>Returns the magic cookie of the local node, if the node is - alive; otherwise the atom <c>nocookie</c>.</p> + <p>Returns the magic cookie of the local node if the node is + alive, otherwise the atom <c>nocookie</c>.</p> + </desc> + </func> + + <func> + <name name="get_keys" arity="0"/> + <fsummary>Return a list of all keys from the process dictionary</fsummary> + <desc> + <p>Returns a list of keys all keys present in the process dictionary.</p> + <pre> +> <input>put(dog, {animal,1}),</input> +<input>put(cow, {animal,2}),</input> +<input>put(lamb, {animal,3}),</input> +<input>get_keys().</input> +[dog,cow,lamb]</pre> </desc> </func> <func> <name name="get_keys" arity="1"/> - <fsummary>Return a list of keys from the process dictionary</fsummary> + <fsummary>Returns a list of keys from the process dictionary.</fsummary> <desc> - <p>Returns a list of keys which are associated with the value - <c><anno>Val</anno></c> in the process dictionary.</p> + <p>Returns a list of keys that are associated with the value + <c><anno>Val</anno></c> in the process dictionary, for example:</p> <pre> > <input>put(mary, {1, 2}),</input> <input>put(had, {1, 2}),</input> @@ -1267,40 +1670,40 @@ true [mary,had,a,little,lamb]</pre> </desc> </func> + <func> <name name="get_stacktrace" arity="0"/> - <fsummary>Get the call stack back-trace of the last exception</fsummary> + <fsummary>Gets the call stack back-trace of the last exception.</fsummary> <type name="stack_item"/> <desc> - <p>Get the call stack back-trace (<em>stacktrace</em>) of the last - exception in the calling process as a list of + <p>Gets the call stack back-trace (<em>stacktrace</em>) of the + last exception in the calling process as a list of <c>{<anno>Module</anno>,<anno>Function</anno>,<anno>Arity</anno>,<anno>Location</anno>}</c> tuples. - The <c><anno>Arity</anno></c> field in the first tuple may be the argument - list of that function call instead of an arity integer, + Field <c><anno>Arity</anno></c> in the first tuple can be the + argument list of that function call instead of an arity integer, depending on the exception.</p> <p>If there has not been any exceptions in a process, the stacktrace is <c>[]</c>. After a code change for the process, - the stacktrace may also be reset to [].</p> + the stacktrace can also be reset to <c>[]</c>.</p> <p>The stacktrace is the same data as the <c>catch</c> operator returns, for example:</p> <p><c>{'EXIT',{badarg,Stacktrace}} = catch abs(x)</c></p> - <p><c><anno>Location</anno></c> is a (possibly empty) list of two-tuples that - may indicate the location in the source code of the function. - The first element is an atom that describes the type of - information in the second element. Currently the following - items may occur:</p> + <p><c><anno>Location</anno></c> is a (possibly empty) list + of two-tuples that + can indicate the location in the source code of the function. + The first element is an atom describing the type of + information in the second element. The following + items can occur:</p> <taglist> <tag><c>file</c></tag> - <item> - <p>The second element of the tuple is a string (list of - characters) representing the filename of the source file - of the function.</p> + <item>The second element of the tuple is a string (list of + characters) representing the file name of the source file + of the function. </item> <tag><c>line</c></tag> - <item> - <p>The second element of the tuple is the line number + <item>The second element of the tuple is the line number (an integer greater than zero) in the source file - where the exception occurred or the function was called.</p> + where the exception occurred or the function was called. </item> </taglist> <p>See also @@ -1308,49 +1711,56 @@ true <seealso marker="#error/2">erlang:error/2</seealso>.</p> </desc> </func> + <func> <name name="group_leader" arity="0"/> - <fsummary>Get the group leader for the calling process</fsummary> + <fsummary>Gets the group leader for the calling process.</fsummary> <desc> - <p>Returns the pid of the group leader for the process which - evaluates the function.</p> + <p>Returns the process identifier of the group leader for the + process evaluating the function.</p> <p>Every process is a member of some process group and all - groups have a <em>group leader</em>. All IO from the group + groups have a <em>group leader</em>. All I/O from the group is channeled to the group leader. When a new process is spawned, it gets the same group leader as the spawning process. Initially, at system start-up, <c>init</c> is both its own group leader and the group leader of all processes.</p> </desc> </func> + <func> <name name="group_leader" arity="2"/> - <fsummary>Set the group leader for a process</fsummary> + <fsummary>Sets the group leader for a process.</fsummary> <desc> - <p>Sets the group leader of <c><anno>Pid</anno></c> to <c><anno>GroupLeader</anno></c>. - Typically, this is used when a processes started from a - certain shell should have another group leader than + <p>Sets the group leader of <c><anno>Pid</anno></c> + to <c><anno>GroupLeader</anno></c>. + Typically, this is used when a process started from a + certain shell is to have another group leader than <c>init</c>.</p> <p>See also <seealso marker="#group_leader/0">group_leader/0</seealso>.</p> </desc> </func> + <func> <name name="halt" arity="0"/> - <fsummary>Halt the Erlang runtime system and indicate normal exit to the calling environment</fsummary> + <fsummary>Halts the Erlang runtime system and indicates normal exit to the calling environment.</fsummary> <desc> <p>The same as <seealso marker="#halt/2"><c>halt(0, [])</c></seealso>.</p> + <p>Example:</p> <pre> > <input>halt().</input> os_prompt% </pre> </desc> </func> + <func> <name name="halt" arity="1"/> - <fsummary>Halt the Erlang runtime system</fsummary> + <fsummary>Halts the Erlang runtime system.</fsummary> <desc> <p>The same as <seealso marker="#halt/2"><c>halt(<anno>Status</anno>, [])</c></seealso>.</p> + <p>Example:</p> <pre> > <input>halt(17).</input> os_prompt% <input>echo $?</input> @@ -1358,178 +1768,188 @@ os_prompt% <input>echo $?</input> os_prompt% </pre> </desc> </func> + <func> <name name="halt" arity="2"/> - <fsummary>Halt the Erlang runtime system</fsummary> + <fsummary>Halts the Erlang runtime system.</fsummary> <desc> <p><c><anno>Status</anno></c> must be a non-negative integer, a string, or the atom <c>abort</c>. Halts the Erlang runtime system. Has no return value. - Depending on <c><anno>Status</anno></c>: - </p> + Depending on <c><anno>Status</anno></c>, the following occurs:</p> <taglist> <tag>integer()</tag> - <item>The runtime system exits with the integer value <c><anno>Status</anno></c> - as status code to the calling environment (operating system). + <item>The runtime system exits with integer value + <c><anno>Status</anno></c> + as status code to the calling environment (OS). </item> <tag>string()</tag> - <item>An erlang crash dump is produced with <c><anno>Status</anno></c> as slogan, - and then the runtime system exits with status code <c>1</c>. + <item>An Erlang crash dump is produced with <c><anno>Status</anno></c> + as slogan. Then the runtime system exits with status code <c>1</c>. </item> <tag><c>abort</c></tag> <item> The runtime system aborts producing a core dump, if that is - enabled in the operating system. + enabled in the OS. </item> </taglist> - <p>Note that on many platforms, only the status codes 0-255 are - supported by the operating system. - </p> - <p>For integer <c><anno>Status</anno></c> the Erlang runtime system closes all ports - and allows async threads to finish their operations before exiting. - To exit without such flushing use - <c><anno>Option</anno></c> as <c>{flush,false}</c>. - </p> - <p>For statuses <c>string()</c> and <c>abort</c> the <c>flush</c> - option is ignored and flushing is <em>not</em> done. - </p> + <note><p>On many platforms, the OS supports only status + codes 0-255.</p></note> + <p>For integer <c><anno>Status</anno></c>, the Erlang runtime system + closes all ports and allows async threads to finish their + operations before exiting. To exit without such flushing, use + <c><anno>Option</anno></c> as <c>{flush,false}</c>.</p> + <p>For statuses <c>string()</c> and <c>abort</c>, option + <c>flush</c> is ignored and flushing is <em>not</em> done.</p> </desc> </func> + <func> <name name="hash" arity="2"/> - <fsummary>Hash function (deprecated)</fsummary> + <fsummary>Hash function (deprecated).</fsummary> <desc> <p>Returns a hash value for <c><anno>Term</anno></c> within the range - <c>1..<anno>Range</anno></c>. The allowed range is 1..2^27-1.</p> + <c>1..<anno>Range</anno></c>. The maximum range is 1..2^27-1.</p> <warning> - <p>This BIF is deprecated as the hash value may differ on - different architectures. Also the hash values for integer - terms larger than 2^27 as well as large binaries are very + <p>This BIF is deprecated, as the hash value can differ on + different architectures. The hash values for integer + terms higher than 2^27 and large binaries are poor. The BIF is retained for backward compatibility - reasons (it may have been used to hash records into a file), - but all new code should use one of the BIFs + reasons (it can have been used to hash records into a file), + but all new code is to use one of the BIFs <c>erlang:phash/2</c> or <c>erlang:phash2/1,2</c> instead.</p> </warning> </desc> </func> + <func> <name name="hd" arity="1"/> - <fsummary>Head of a list</fsummary> + <fsummary>Head of a list.</fsummary> <desc> - <p>Returns the head of <c><anno>List</anno></c>, that is, the first element.</p> + <p>Returns the head of <c><anno>List</anno></c>, that is, + the first element, for example:</p> <pre> > <input>hd([1,2,3,4,5]).</input> 1</pre> <p>Allowed in guard tests.</p> - <p>Failure: <c>badarg</c> if <c><anno>List</anno></c> is the empty list [].</p> + <p>Failure: <c>badarg</c> if <c><anno>List</anno></c> is the empty + list <c>[]</c>.</p> </desc> </func> + <func> <name name="hibernate" arity="3"/> - <fsummary>Hibernate a process until a message is sent to it</fsummary> + <fsummary>Hibernates a process until a message is sent to it.</fsummary> <desc> <p>Puts the calling process into a wait state where its memory - allocation has been reduced as much as possible, which is + allocation has been reduced as much as possible. This is useful if the process does not expect to receive any messages - in the near future.</p> - <p>The process will be awaken when a message is sent to it, and - control will resume in <c><anno>Module</anno>:<anno>Function</anno></c> with - the arguments given by <c><anno>Args</anno></c> with the call stack - emptied, meaning that the process will terminate when that - function returns. Thus <c>erlang:hibernate/3</c> will never - return to its caller.</p> + soon.</p> + <p>The process is awaken when a message is sent to it, and control + resumes in <c><anno>Module</anno>:<anno>Function</anno></c> with + the arguments given by <c><anno>Args</anno></c> with the call + stack emptied, meaning that the process terminates when that + function returns. Thus <c>erlang:hibernate/3</c> never + returns to its caller.</p> <p>If the process has any message in its message queue, - the process will be awaken immediately in the same way as - described above.</p> + the process is awakened immediately in the same way as + described earlier.</p> <p>In more technical terms, what <c>erlang:hibernate/3</c> does - is the following. It discards the call stack for the process. - Then it garbage collects the process. After the garbage - collection, all live data is in one continuous heap. The heap + is the following. It discards the call stack for the process, + and then garbage collects the process. After this, + all live data is in one continuous heap. The heap is then shrunken to the exact same size as the live data - which it holds (even if that size is less than the minimum + that it holds (even if that size is less than the minimum heap size for the process).</p> <p>If the size of the live data in the process is less than the minimum heap size, the first garbage collection occurring - after the process has been awaken will ensure that the heap + after the process is awakened ensures that the heap size is changed to a size not smaller than the minimum heap size.</p> - <p>Note that emptying the call stack means that any surrounding - <c>catch</c> is removed and has to be re-inserted after + <p>Notice that emptying the call stack means that any surrounding + <c>catch</c> is removed and must be reinserted after hibernation. One effect of this is that processes started using <c>proc_lib</c> (also indirectly, such as - <c>gen_server</c> processes), should use + <c>gen_server</c> processes), are to use <seealso marker="stdlib:proc_lib#hibernate/3">proc_lib:hibernate/3</seealso> - instead to ensure that the exception handler continues to work + instead, to ensure that the exception handler continues to work when the process wakes up.</p> </desc> </func> <func> <name name="insert_element" arity="3"/> - <fsummary>Insert an element at index in a tuple</fsummary> + <fsummary>Inserts an element at index in a tuple.</fsummary> <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno>) + 1</type_desc> <desc> - <p> - Returns a new tuple with element <c><anno>Term</anno></c> insert at position - <c><anno>Index</anno></c> in tuple <c><anno>Tuple1</anno></c>. - All elements from position <c><anno>Index</anno></c> and upwards are subsequently - pushed one step higher in the new tuple <c><anno>Tuple2</anno></c>. - </p> + <p>Returns a new tuple with element <c><anno>Term</anno></c> + inserted at position + <c><anno>Index</anno></c> in tuple <c><anno>Tuple1</anno></c>. + All elements from position <c><anno>Index</anno></c> and upwards are + pushed one step higher in the new tuple <c><anno>Tuple2</anno></c>.</p> + <p>Example:</p> <pre> > <input>erlang:insert_element(2, {one, two, three}, new).</input> {one,new,two,three}</pre> </desc> </func> + <func> <name name="integer_to_binary" arity="1"/> - <fsummary>Text representation of an integer</fsummary> + <fsummary>Text representation of an integer.</fsummary> <desc> - <p>Returns a binary which corresponds to the text - representation of <c><anno>Integer</anno></c>.</p> + <p>Returns a binary corresponding to the text + representation of <c><anno>Integer</anno></c>, for example:</p> <pre> > <input>integer_to_binary(77).</input> <<"77">></pre> </desc> </func> + <func> <name name="integer_to_binary" arity="2"/> - <fsummary>Text representation of an integer</fsummary> + <fsummary>Text representation of an integer.</fsummary> <desc> - <p>Returns a binary which corresponds to the text - representation of <c><anno>Integer</anno></c> in base <c><anno>Base</anno></c>.</p> + <p>Returns a binary corresponding to the text + representation of <c><anno>Integer</anno></c> in base + <c><anno>Base</anno></c>, for example:</p> <pre> > <input>integer_to_binary(1023, 16).</input> <<"3FF">></pre> </desc> </func> + <func> <name name="integer_to_list" arity="1"/> - <fsummary>Text representation of an integer</fsummary> + <fsummary>Text representation of an integer.</fsummary> <desc> - <p>Returns a string which corresponds to the text - representation of <c><anno>Integer</anno></c>.</p> + <p>Returns a string corresponding to the text + representation of <c><anno>Integer</anno></c>, for example:</p> <pre> > <input>integer_to_list(77).</input> "77"</pre> </desc> </func> + <func> <name name="integer_to_list" arity="2"/> - <fsummary>Text representation of an integer</fsummary> + <fsummary>Text representation of an integer.</fsummary> <desc> - <p>Returns a string which corresponds to the text - representation of <c><anno>Integer</anno></c> in base <c><anno>Base</anno></c>.</p> + <p>Returns a string corresponding to the text + representation of <c><anno>Integer</anno></c> in base + <c><anno>Base</anno></c>, for example:</p> <pre> > <input>integer_to_list(1023, 16).</input> "3FF"</pre> </desc> </func> + <func> <name name="iolist_to_binary" arity="1"/> - <fsummary>Convert an iolist to a binary</fsummary> + <fsummary>Converts an iolist to a binary.</fsummary> <desc> - <p>Returns a binary which is made from the integers and - binaries in <c><anno>IoListOrBinary</anno></c>.</p> + <p>Returns a binary that is made from the integers and + binaries in <c><anno>IoListOrBinary</anno></c>, for example:</p> <pre> > <input>Bin1 = <<1,2,3>>.</input> <<1,2,3>> @@ -1541,269 +1961,311 @@ os_prompt% </pre> <<1,2,3,1,2,3,4,5,4,6>></pre> </desc> </func> + <func> <name name="iolist_size" arity="1"/> - <fsummary>Size of an iolist</fsummary> + <fsummary>Size of an iolist.</fsummary> <desc> - <p>Returns an integer which is the size in bytes - of the binary that would be the result of - <c>iolist_to_binary(<anno>Item</anno>)</c>.</p> + <p>Returns an integer that is the size in bytes + of the binary that would be the result of + <c>iolist_to_binary(<anno>Item</anno>)</c>, for example:</p> <pre> > <input>iolist_size([1,2|<<3,4>>]).</input> 4</pre> </desc> </func> + <func> <name name="is_alive" arity="0"/> - <fsummary>Check whether the local node is alive</fsummary> + <fsummary>Checks whether the local node is alive.</fsummary> <desc> - <p>Returns <c>true</c> if the local node is alive; that is, if - the node can be part of a distributed system. Otherwise, it - returns <c>false</c>.</p> + <p>Returns <c>true</c> if the local node is alive (that is, if + the node can be part of a distributed system), otherwise + <c>false</c>.</p> </desc> </func> + <func> <name name="is_atom" arity="1"/> - <fsummary>Check whether a term is an atom</fsummary> + <fsummary>Checks whether a term is an atom.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an atom; - otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an atom, + otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_binary" arity="1"/> - <fsummary>Check whether a term is a binary</fsummary> + <fsummary>Checks whether a term is a binary.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a binary; - otherwise returns <c>false</c>.</p> - + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a binary, + otherwise <c>false</c>.</p> <p>A binary always contains a complete number of bytes.</p> - <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_bitstring" arity="1"/> - <fsummary>Check whether a term is a bitstring</fsummary> + <fsummary>Checks whether a term is a bitstring.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a bitstring (including a binary); - otherwise returns <c>false</c>.</p> - + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a + bitstring (including a binary), otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_boolean" arity="1"/> - <fsummary>Check whether a term is a boolean</fsummary> + <fsummary>Checks whether a term is a boolean.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is - either the atom <c>true</c> or the atom <c>false</c> - (i.e. a boolean); otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is the + atom <c>true</c> or the atom <c>false</c> (that is, a boolean). + Otherwise returns <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_builtin" arity="3"/> - <fsummary>Check if a function is a BIF implemented in C</fsummary> + <fsummary>Checks if a function is a BIF implemented in C.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Module</anno>:<anno>Function</anno>/<anno>Arity</anno></c> is - a BIF implemented in C; otherwise returns <c>false</c>. - This BIF is useful for builders of cross reference tools.</p> + <p>This BIF is useful for builders of cross-reference tools.</p> + <p>Returns <c>true</c> if + <c><anno>Module</anno>:<anno>Function</anno>/<anno>Arity</anno></c> + is a BIF implemented in C, otherwise <c>false</c>.</p> </desc> </func> + <func> <name name="is_float" arity="1"/> - <fsummary>Check whether a term is a float</fsummary> + <fsummary>Checks whether a term is a float.</fsummary> <desc> <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a floating point - number; otherwise returns <c>false</c>.</p> + number, otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_function" arity="1"/> - <fsummary>Check whether a term is a fun</fsummary> + <fsummary>Checks whether a term is a fun.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a fun; otherwise - returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a fun, otherwise + <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_function" arity="2"/> - <fsummary>Check whether a term is a fun with a given arity</fsummary> + <fsummary>Checks whether a term is a fun with a given arity.</fsummary> <desc> <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a fun that can be - applied with <c><anno>Arity</anno></c> number of arguments; otherwise - returns <c>false</c>.</p> + applied with <c><anno>Arity</anno></c> number of arguments, otherwise + <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_integer" arity="1"/> - <fsummary>Check whether a term is an integer</fsummary> + <fsummary>Checks whether a term is an integer.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an integer; - otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an integer, + otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_list" arity="1"/> - <fsummary>Check whether a term is a list</fsummary> + <fsummary>Checks whether a term is a list.</fsummary> <desc> <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a list with - zero or more elements; otherwise returns <c>false</c>.</p> + zero or more elements, otherwise <c>false</c>.</p> + <p>Allowed in guard tests.</p> + </desc> + </func> + + <func> + <name name="is_map" arity="1"/> + <fsummary>Checks whether a term is a map.</fsummary> + <desc> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a map, + otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_number" arity="1"/> - <fsummary>Check whether a term is a number</fsummary> + <fsummary>Checks whether a term is a number.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is either an integer or a - floating point number; otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is an integer or a + floating point number. Otherwise returns <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_pid" arity="1"/> - <fsummary>Check whether a term is a pid</fsummary> + <fsummary>Checks whether a term is a process identifier.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a pid (process - identifier); otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a process + identifier, otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_port" arity="1"/> - <fsummary>Check whether a term is a port</fsummary> + <fsummary>Checks whether a term is a port.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a port identifier; - otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a port identifier, + otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_process_alive" arity="1"/> - <fsummary>Check whether a process is alive</fsummary> + <fsummary>Checks whether a process is alive.</fsummary> <desc> - <p> - <c><anno>Pid</anno></c> must refer to a process at the local node. - Returns <c>true</c> if the process exists and is alive, that - is, is not exiting and has not exited. Otherwise, returns + <p><c><anno>Pid</anno></c> must refer to a process at the local node.</p> + <p>Returns <c>true</c> if the process exists and is alive, that + is, is not exiting and has not exited. Otherwise returns <c>false</c>. </p> </desc> </func> + <func> <name name="is_record" arity="2"/> - <fsummary>Check whether a term appears to be a record</fsummary> + <fsummary>Checks whether a term appears to be a record.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a tuple and its first - element is <c><anno>RecordTag</anno></c>. Otherwise, returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a tuple and its + first element is <c><anno>RecordTag</anno></c>. + Otherwise returns <c>false</c>.</p> <note> <p>Normally the compiler treats calls to <c>is_record/2</c> - specially. It emits code to verify that <c><anno>Term</anno></c> is a - tuple, that its first element is <c><anno>RecordTag</anno></c>, and that - the size is correct. However, if the <c><anno>RecordTag</anno></c> is - not a literal atom, the <c>is_record/2</c> BIF will be - called instead and the size of the tuple will not be - verified.</p> + specially. It emits code to verify that <c><anno>Term</anno></c> + is a tuple, that its first element is + <c><anno>RecordTag</anno></c>, and that the + size is correct. However, if <c><anno>RecordTag</anno></c> is + not a literal atom, the BIF <c>is_record/2</c> is called + instead and the size of the tuple is not verified.</p> </note> - <p>Allowed in guard tests, if <c><anno>RecordTag</anno></c> is a literal - atom.</p> + <p>Allowed in guard tests, if <c><anno>RecordTag</anno></c> is + a literal atom.</p> </desc> </func> + <func> <name name="is_record" arity="3"/> - <fsummary>Check whether a term appears to be a record</fsummary> - <desc> - <p><c><anno>RecordTag</anno></c> must be an atom. Returns <c>true</c> if - <c><anno>Term</anno></c> is a tuple, its first element is <c><anno>RecordTag</anno></c>, - and its size is <c><anno>Size</anno></c>. Otherwise, returns <c>false</c>.</p> - <p>Allowed in guard tests, provided that <c><anno>RecordTag</anno></c> is + <fsummary>Checks whether a term appears to be a record.</fsummary> + <desc> + <p><c><anno>RecordTag</anno></c> must be an atom.</p> + <p>Returns <c>true</c> if + <c><anno>Term</anno></c> is a tuple, + its first element is <c><anno>RecordTag</anno></c>, + and its size is <c><anno>Size</anno></c>. + Otherwise returns <c>false</c>.</p> + <p>Allowed in guard tests if <c><anno>RecordTag</anno></c> is a literal atom and <c>Size</c> is a literal integer.</p> <note> - <p>This BIF is documented for completeness. In most cases - <c>is_record/2</c> should be used.</p> + <p>This BIF is documented for completeness. Usually + <c>is_record/2</c> is to be used.</p> </note> </desc> </func> + <func> <name name="is_reference" arity="1"/> - <fsummary>Check whether a term is a reference</fsummary> + <fsummary>Checks whether a term is a reference.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a reference; - otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a reference, + otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="is_tuple" arity="1"/> - <fsummary>Check whether a term is a tuple</fsummary> + <fsummary>Checks whether a term is a tuple.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a tuple; - otherwise returns <c>false</c>.</p> + <p>Returns <c>true</c> if <c><anno>Term</anno></c> is a tuple, + otherwise <c>false</c>.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="length" arity="1"/> - <fsummary>Length of a list</fsummary> + <fsummary>Length of a list.</fsummary> <desc> - <p>Returns the length of <c><anno>List</anno></c>.</p> + <p>Returns the length of <c><anno>List</anno></c>, for example:</p> <pre> > <input>length([1,2,3,4,5,6,7,8,9]).</input> 9</pre> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="link" arity="1"/> - <fsummary>Create a link to another process (or port)</fsummary> + <fsummary>Creates a link to another process (or port).</fsummary> <desc> <p>Creates a link between the calling process and another - process (or port) <c><anno>PidOrPort</anno></c>, if there is not such a link + process (or port) <c><anno>PidOrPort</anno></c>, if there is + not such a link already. If a process attempts to create a link to itself, nothing is done. Returns <c>true</c>.</p> - <p>If <c><anno>PidOrPort</anno></c> does not exist, the behavior of the BIF depends - on if the calling process is trapping exits or not (see + <p>If <c><anno>PidOrPort</anno></c> does not exist, the behavior + of the BIF + depends on if the calling process is trapping exits or not (see <seealso marker="#process_flag/2">process_flag/2</seealso>):</p> <list type="bulleted"> <item>If the calling process is not trapping exits, and - checking <c><anno>PidOrPort</anno></c> is cheap -- that is, if <c><anno>PidOrPort</anno></c> is - local -- <c>link/1</c> fails with reason <c>noproc</c>.</item> + checking <c><anno>PidOrPort</anno></c> is cheap + (that is, if <c><anno>PidOrPort</anno></c> + is local), <c>link/1</c> fails with reason <c>noproc</c>.</item> <item>Otherwise, if the calling process is trapping exits, - and/or <c><anno>PidOrPort</anno></c> is remote, <c>link/1</c> returns - <c>true</c>, but an exit signal with reason <c>noproc</c> + and/or <c><anno>PidOrPort</anno></c> is remote, <c>link/1</c> + returns <c>true</c>, but an exit signal with reason <c>noproc</c> is sent to the calling process.</item> </list> </desc> </func> + <func> <name name="list_to_atom" arity="1"/> - <fsummary>Convert from text representation to an atom</fsummary> - <desc> - <p>Returns the atom whose text representation is <c><anno>String</anno></c>.</p> - <p><c><anno>String</anno></c> may only contain ISO-latin-1 - characters (i.e. numbers below 256) as the current - implementation does not allow unicode characters >= 256 in - atoms. For more information on Unicode support in atoms - see <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8 encoded atoms</seealso> - in the chapter about the external term format in the ERTS User's Guide.</p> + <fsummary>Converts from text representation to an atom.</fsummary> + <desc> + <p>Returns the atom whose text representation is + <c><anno>String</anno></c>.</p> + <p><c><anno>String</anno></c> can only contain ISO-latin-1 + characters (that is, + numbers less than 256) as the implementation does not + allow unicode characters equal to or above 256 in atoms. + For more information on Unicode support in atoms, see + <seealso marker="erl_ext_dist#utf8_atoms">note on UTF-8 + encoded atoms</seealso> + in Section "External Term Format" in the User's Guide.</p> + <p>Example:</p> <pre> > <input>list_to_atom("Erlang").</input> 'Erlang'</pre> </desc> </func> + <func> <name name="list_to_binary" arity="1"/> - <fsummary>Convert a list to a binary</fsummary> + <fsummary>Converts a list to a binary.</fsummary> <desc> - <p>Returns a binary which is made from the integers and - binaries in <c><anno>IoList</anno></c>.</p> + <p>Returns a binary that is made from the integers and + binaries in <c><anno>IoList</anno></c>, for example:</p> <pre> > <input>Bin1 = <<1,2,3>>.</input> <<1,2,3>> @@ -1815,40 +2277,46 @@ os_prompt% </pre> <<1,2,3,1,2,3,4,5,4,6>></pre> </desc> </func> + <func> <name name="list_to_bitstring" arity="1"/> + <fsummary>Converts a list to a bitstring.</fsummary> <type name="bitstring_list"/> - <fsummary>Convert a list to a bitstring</fsummary> <desc> - <p>Returns a bitstring which is made from the integers and - bitstrings in <c><anno>BitstringList</anno></c>. (The last tail in <c><anno>BitstringList</anno></c> - is allowed to be a bitstring.)</p> + <p>Returns a bitstring that is made from the integers and + bitstrings in <c><anno>BitstringList</anno></c>. (The last tail in + <c><anno>BitstringList</anno></c> is allowed to be a bitstring.)</p> + <p>Example:</p> <pre> > <input>Bin1 = <<1,2,3>>.</input> <<1,2,3>> > <input>Bin2 = <<4,5>>.</input> <<4,5>> -> <input>Bin3 = <<6,7:4,>>.</input> -<<6>> +> <input>Bin3 = <<6,7:4>>.</input> +<<6,7:4>> > <input>list_to_bitstring([Bin1,1,[2,3,Bin2],4|Bin3]).</input> -<<1,2,3,1,2,3,4,5,4,6,7:46>></pre> +<<1,2,3,1,2,3,4,5,4,6,7:4>></pre> </desc> </func> + <func> <name name="list_to_existing_atom" arity="1"/> - <fsummary>Convert from text representation to an atom</fsummary> + <fsummary>Converts from text representation to an atom.</fsummary> <desc> - <p>Returns the atom whose text representation is <c><anno>String</anno></c>, + <p>Returns the atom whose text representation is + <c><anno>String</anno></c>, but only if there already exists such atom.</p> <p>Failure: <c>badarg</c> if there does not already exist an atom whose text representation is <c><anno>String</anno></c>.</p> </desc> </func> + <func> <name name="list_to_float" arity="1"/> - <fsummary>Convert from text representation to a float</fsummary> + <fsummary>Converts from text representation to a float.</fsummary> <desc> - <p>Returns the float whose text representation is <c><anno>String</anno></c>.</p> + <p>Returns the float whose text representation is + <c><anno>String</anno></c>, for example:</p> <pre> > <input>list_to_float("2.2017764e+0").</input> 2.2017764</pre> @@ -1856,12 +2324,13 @@ os_prompt% </pre> representation of a float.</p> </desc> </func> + <func> <name name="list_to_integer" arity="1"/> - <fsummary>Convert from text representation to an integer</fsummary> + <fsummary>Converts from text representation to an integer.</fsummary> <desc> <p>Returns an integer whose text representation is - <c><anno>String</anno></c>.</p> + <c><anno>String</anno></c>, for example:</p> <pre> > <input>list_to_integer("123").</input> 123</pre> @@ -1869,12 +2338,14 @@ os_prompt% </pre> representation of an integer.</p> </desc> </func> + <func> <name name="list_to_integer" arity="2"/> - <fsummary>Convert from text representation to an integer</fsummary> + <fsummary>Converts from text representation to an integer.</fsummary> <desc> <p>Returns an integer whose text representation in base - <c><anno>Base</anno></c> is <c><anno>String</anno></c>.</p> + <c><anno>Base</anno></c> is <c><anno>String</anno></c>, + for example:</p> <pre> > <input>list_to_integer("3FF", 16).</input> 1023</pre> @@ -1882,47 +2353,52 @@ os_prompt% </pre> representation of an integer.</p> </desc> </func> + <func> <name name="list_to_pid" arity="1"/> - <fsummary>Convert from text representation to a pid</fsummary> + <fsummary>Converts from text representation to a pid.</fsummary> <desc> - <p>Returns a pid whose text representation is <c><anno>String</anno></c>.</p> - <warning> - <p>This BIF is intended for debugging and for use in - the Erlang operating system. It should not be used in - application programs.</p> - </warning> + <p>Returns a process identifier whose text representation is a + <c><anno>String</anno></c>, for example:</p> <pre> > <input>list_to_pid("<0.4.1>").</input> <0.4.1></pre> <p>Failure: <c>badarg</c> if <c><anno>String</anno></c> contains a bad - representation of a pid.</p> + representation of a process identifier.</p> + <warning> + <p>This BIF is intended for debugging and is not to be used + in application programs.</p> + </warning> </desc> </func> + <func> <name name="list_to_tuple" arity="1"/> - <fsummary>Convert a list to a tuple</fsummary> + <fsummary>Converts a list to a tuple.</fsummary> <desc> - <p>Returns a tuple which corresponds to <c><anno>List</anno></c>. <c><anno>List</anno></c> - can contain any Erlang terms.</p> + <p>Returns a tuple corresponding to <c><anno>List</anno></c>, + for example</p> <pre> > <input>list_to_tuple([share, ['Ericsson_B', 163]]).</input> {share, ['Ericsson_B', 163]}</pre> + <p><c><anno>List</anno></c> can contain any Erlang terms.</p> </desc> </func> + <func> <name name="load_module" arity="2"/> - <fsummary>Load object code for a module</fsummary> + <fsummary>Loads object code for a module.</fsummary> <desc> - <p>If <c><anno>Binary</anno></c> contains the object code for the module - <c><anno>Module</anno></c>, this BIF loads that object code. Also, if - the code for the module <c><anno>Module</anno></c> already exists, all + <p>If <c><anno>Binary</anno></c> contains the object code for module + <c><anno>Module</anno></c>, this BIF loads that object code. If + the code for module <c><anno>Module</anno></c> already exists, all export references are replaced so they point to the newly loaded code. The previously loaded code is kept in the system - as old code, as there may still be processes which are - executing that code. It returns either - <c>{module, <anno>Module</anno>}</c>, or <c>{error, <anno>Reason</anno>}</c> if loading - fails. <c><anno>Reason</anno></c> is one of the following:</p> + as old code, as there can still be processes executing + that code.</p> + <p>Returns either <c>{module, <anno>Module</anno>}</c>, or + <c>{error, <anno>Reason</anno>}</c> if loading fails. + <c><anno>Reason</anno></c> is any of the following:</p> <taglist> <tag><c>badfile</c></tag> <item> @@ -1932,118 +2408,122 @@ os_prompt% </pre> </item> <tag><c>not_purged</c></tag> <item> - <p><c><anno>Binary</anno></c> contains a module which cannot be loaded - because old code for this module already exists.</p> + <p><c><anno>Binary</anno></c> contains a module that cannot be + loaded because old code for this module already exists.</p> </item> </taglist> <warning> <p>This BIF is intended for the code server (see - <seealso marker="kernel:code">code(3)</seealso>) and should not be - used elsewhere.</p> + <seealso marker="kernel:code">code(3)</seealso>) + and is not to be used elsewhere.</p> </warning> </desc> </func> + <func> <name name="load_nif" arity="2"/> - <fsummary>Load NIF library</fsummary> + <fsummary>Loads NIF library.</fsummary> <desc> <note> - <p>In releases older than OTP R14B, NIFs were an - experimental feature. Versions of OTP older than R14B might + <p>Before OTP R14B, NIFs were an + experimental feature. Versions before OTP R14B can have different and possibly incompatible NIF semantics and - interfaces. For example, in R13B03 the return value on - failure was - <c>{error,Reason,Text}</c>.</p> + interfaces. For example, in OTP R13B03 the return value on + failure was <c>{error,Reason,Text}</c>.</p> </note> <p>Loads and links a dynamic library containing native - implemented functions (NIFs) for a module. <c><anno>Path</anno></c> is a - file path to the sharable object/dynamic library file minus - the OS-dependent file extension (.so for Unix and .dll for - Windows). See <seealso marker="erl_nif">erl_nif</seealso> - on how to implement a NIF library.</p> - <p><c><anno>LoadInfo</anno></c> can be any term. It will be passed on to + implemented functions (NIFs) for a module. <c><anno>Path</anno></c> + is a file path to the shareable object/dynamic library file minus + the OS-dependent file extension (<c>.so</c> for Unix and + <c>.dll</c> for Windows. For information on how to + implement a NIF library, see + <seealso marker="erl_nif">erl_nif</seealso>.</p> + <p><c><anno>LoadInfo</anno></c> can be any term. It is passed on to the library as part of the initialization. A good practice is to include a module version number to support future code upgrade scenarios.</p> <p>The call to <c>load_nif/2</c> must be made <em>directly</em> from the Erlang code of the module that the - NIF library belongs to.</p> - <p>It returns either <c>ok</c>, or <c>{error,{<anno>Reason</anno>,Text}}</c> - if loading fails. <c><anno>Reason</anno></c> is one of the atoms below, - while <c><anno>Text</anno></c> is a human readable string that may give - some more information about the failure.</p> + NIF library belongs to. It returns either <c>ok</c>, or + <c>{error,{<anno>Reason</anno>,Text}}</c> if loading fails. + <c><anno>Reason</anno></c> is one of the following atoms + while <c><anno>Text</anno></c> is a human readable string that + can give more information about the failure:</p> <taglist> <tag><c>load_failed</c></tag> - <item> - <p>The OS failed to load the NIF library.</p> + <item>The OS failed to load the NIF library. </item> <tag><c>bad_lib</c></tag> - <item> - <p>The library did not fulfil the requirements as a NIF - library of the calling module.</p> + <item>The library did not fulfill the requirements as a NIF + library of the calling module. </item> <tag><c>load | reload | upgrade</c></tag> - <item> - <p>The corresponding library callback was not successful.</p> + <item>The corresponding library callback was unsuccessful. </item> <tag><c>old_code</c></tag> - <item> - <p>The call to <c>load_nif/2</c> was made from the old - code of a module that has been upgraded. This is not - allowed.</p> + <item>The call to <c>load_nif/2</c> was made from the old + code of a module that has been upgraded; this is not + allowed. </item> </taglist> </desc> </func> + <func> <name name="loaded" arity="0"/> - <fsummary>List of all loaded modules</fsummary> + <fsummary>Lists all loaded modules.</fsummary> <desc> - <p>Returns a list of all loaded Erlang modules (current and/or + <p>Returns a list of all loaded Erlang modules (current and old code), including preloaded modules.</p> <p>See also <seealso marker="kernel:code">code(3)</seealso>.</p> </desc> </func> + <func> <name name="localtime" arity="0"/> - <fsummary>Current local date and time</fsummary> + <fsummary>Current local date and time.</fsummary> <desc> - <p>Returns the current local date and time - <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c>.</p> - <p>The time zone and daylight saving time correction depend - on the underlying OS.</p> + <p>Returns the current local date and time, + <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c>, + for example:</p> <pre> > <input>erlang:localtime().</input> {{1996,11,6},{14,45,17}}</pre> + <p>The time zone and Daylight Saving Time correction depend + on the underlying OS.</p> </desc> </func> + <func> <name name="localtime_to_universaltime" arity="1"/> - <fsummary>Convert from local to Universal Time Coordinated (UTC) date and time</fsummary> + <fsummary>Converts from local to Universal Time Coordinated (UTC) date and time.</fsummary> <desc> <p>Converts local date and time to Universal Time Coordinated - (UTC), if this is supported by the underlying OS. Otherwise, - no conversion is done and <c><anno>Localtime</anno></c> is returned.</p> + (UTC), if supported by the underlying OS. Otherwise + no conversion is done and <c><anno>Localtime</anno></c> + is returned.</p> + <p>Example:</p> <pre> > <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}).</input> {{1996,11,6},{13,45,17}}</pre> - <p>Failure: <c>badarg</c> if <c><anno>Localtime</anno></c> does not denote - a valid date and time.</p> + <p>Failure: <c>badarg</c> if <c><anno>Localtime</anno></c> denotes an + invalid date and time.</p> </desc> </func> + <func> <name name="localtime_to_universaltime" arity="2"/> - <fsummary>Convert from local to Universal Time Coordinated (UTC) date and time</fsummary> + <fsummary>Converts from local to Universal Time Coordinated (UTC) date and time.</fsummary> <desc> <p>Converts local date and time to Universal Time Coordinated - (UTC) just like <c>erlang:localtime_to_universaltime/1</c>, - but the caller decides if daylight saving time is active or - not.</p> - <p>If <c><anno>IsDst</anno> == true</c> the <c><anno>Localtime</anno></c> is during - daylight saving time, if <c><anno>IsDst</anno> == false</c> it is not, - and if <c><anno>IsDst</anno> == undefined</c> the underlying OS may + (UTC) as <c>erlang:localtime_to_universaltime/1</c>, + but the caller decides if Daylight Saving Time is active.</p> + <p>If <c><anno>IsDst</anno> == true</c>, <c><anno>Localtime</anno></c> is + during Daylight Saving Time, if <c><anno>IsDst</anno> == false</c> it is + not. If <c><anno>IsDst</anno> == undefined</c>, the underlying OS can guess, which is the same as calling <c>erlang:localtime_to_universaltime(<anno>Localtime</anno>)</c>.</p> + <p>Examples:</p> <pre> > <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, true).</input> {{1996,11,6},{12,45,17}} @@ -2051,205 +2531,227 @@ os_prompt% </pre> {{1996,11,6},{13,45,17}} > <input>erlang:localtime_to_universaltime({{1996,11,6},{14,45,17}}, undefined).</input> {{1996,11,6},{13,45,17}}</pre> - <p>Failure: <c>badarg</c> if <c><anno>Localtime</anno></c> does not denote - a valid date and time.</p> + <p>Failure: <c>badarg</c> if <c><anno>Localtime</anno></c> denotes an + invalid date and time.</p> </desc> </func> + <func> <name name="make_ref" arity="0"/> - <fsummary>Return an almost unique reference</fsummary> + <fsummary>Returns a unique reference.</fsummary> <desc> - <p>Returns an almost unique reference.</p> - <p>The returned reference will re-occur after approximately 2^82 - calls; therefore it is unique enough for practical purposes.</p> - <pre> -> <input>make_ref().</input> -#Ref<0.0.0.135></pre> + <p>Returns a <seealso marker="doc/efficiency_guide:advanced#unique_references">unique + reference</seealso>. The reference is unique among + connected nodes.</p> + <warning><p>Known issue: When a node is restarted multiple + times with the same node name, references created + on a newer node can be mistaken for a reference + created on an older node with the same node name.</p></warning> </desc> </func> + <func> <name name="make_tuple" arity="2"/> - <fsummary>Create a new tuple of a given arity</fsummary> + <fsummary>Creates a new tuple of a given arity.</fsummary> <desc> - <p>Returns a new tuple of the given <c><anno>Arity</anno></c>, where all - elements are <c><anno>InitialValue</anno></c>.</p> + <p>Creates a new tuple of the given <c><anno>Arity</anno></c>, where all + elements are <c><anno>InitialValue</anno></c>, for example:</p> <pre> > <input>erlang:make_tuple(4, []).</input> {[],[],[],[]}</pre> </desc> </func> + <func> <name name="make_tuple" arity="3"/> - <fsummary>Create a new tuple with given arity and contents</fsummary> - <desc> - <p><c>erlang:make_tuple</c> first creates a tuple of size <c><anno>Arity</anno></c> - where each element has the value <c><anno>DefaultValue</anno></c>. It then fills - in values from <c><anno>InitList</anno></c>. Each list element in <c><anno>InitList</anno></c> - must be a two-tuple where the first element is a position in the - newly created tuple and the second element is any term. If a position - occurs more than once in the list, the term corresponding to - last occurrence will be used.</p> + <fsummary>Creates a new tuple with given arity and contents.</fsummary> + <desc> + <p>Creates a tuple of size <c><anno>Arity</anno></c>, where each element + has value <c><anno>DefaultValue</anno></c>, and then fills in + values from <c><anno>InitList</anno></c>. + Each list element in <c><anno>InitList</anno></c> + must be a two-tuple, where the first element is a position in the + newly created tuple and the second element is any term. If a + position occurs more than once in the list, the term corresponding + to the last occurrence is used.</p> + <p>Example:</p> <pre> > <input>erlang:make_tuple(5, [], [{2,ignored},{5,zz},{2,aa}]).</input> {{[],aa,[],[],zz}</pre> </desc> </func> + + <func> + <name name="map_size" arity="1"/> + <fsummary>Returns the size of a map.</fsummary> + <desc> + <p>Returns an integer, which is the number of key-value pairs + in <c><anno>Map</anno></c>, for example:</p> + <pre> +> <input>map_size(#{a=>1, b=>2, c=>3}).</input> +3</pre> + <p>Allowed in guard tests.</p> + </desc> + </func> + <func> <name name="max" arity="2"/> - <fsummary>Return the largest of two term</fsummary> + <fsummary>Returns the largest of two terms.</fsummary> <desc> - <p>Return the largest of <c><anno>Term1</anno></c> and <c><anno>Term2</anno></c>; - if the terms compare equal, <c><anno>Term1</anno></c> will be returned.</p> + <p>Returns the largest of <c><anno>Term1</anno></c> and + <c><anno>Term2</anno></c>. + If the terms are equal, <c><anno>Term1</anno></c> is returned.</p> </desc> </func> + <func> <name name="md5" arity="1"/> - <fsummary>Compute an MD5 message digest</fsummary> + <fsummary>Computes an MD5 message digest.</fsummary> <desc> - <p>Computes an <c>MD5</c> message digest from <c><anno>Data</anno></c>, where - the length of the digest is 128 bits (16 bytes). <c><anno>Data</anno></c> + <p>Computes an MD5 message digest from <c><anno>Data</anno></c>, where + the length of the digest is 128 bits (16 bytes). + <c><anno>Data</anno></c> is a binary or a list of small integers and binaries.</p> - <p>See The MD5 Message Digest Algorithm (RFC 1321) for more - information about MD5.</p> - <warning><p>The MD5 Message Digest Algorithm is <em>not</em> considered - safe for code-signing or software integrity purposes.</p></warning> + <p>For more information about MD5, see RFC 1321 - The + MD5 Message-Digest Algorithm.</p> + <warning><p>The MD5 Message-Digest Algorithm is <em>not</em> considered + safe for code-signing or software-integrity purposes.</p></warning> </desc> </func> + <func> <name name="md5_final" arity="1"/> - <fsummary>Finish the update of an MD5 context and return the computed MD5 message digest</fsummary> + <fsummary>Finishes the update of an MD5 context and returns the computed MD5 message digest.</fsummary> <desc> <p>Finishes the update of an MD5 <c><anno>Context</anno></c> and returns the computed <c>MD5</c> message digest.</p> </desc> </func> + <func> <name name="md5_init" arity="0"/> - <fsummary>Create an MD5 context</fsummary> + <fsummary>Creates an MD5 context.</fsummary> <desc> <p>Creates an MD5 context, to be used in subsequent calls to <c>md5_update/2</c>.</p> </desc> </func> + <func> <name name="md5_update" arity="2"/> - <fsummary>Update an MD5 context with data, and return a new context</fsummary> + <fsummary>Updates an MD5 context with data and returns a new context.</fsummary> <desc> - <p>Updates an MD5 <c><anno>Context</anno></c> with <c><anno>Data</anno></c>, and returns - a <c><anno>NewContext</anno></c>.</p> + <p>Updates an MD5 <c><anno>Context</anno></c> with + <c><anno>Data</anno></c> and returns a + <c><anno>NewContext</anno></c>.</p> </desc> </func> + <func> <name name="memory" arity="0"/> + <fsummary>Information about dynamically allocated memory.</fsummary> <type name="memory_type"/> - <fsummary>Information about dynamically allocated memory</fsummary> - <desc> - <p>Returns a list containing information about memory - dynamically allocated by the Erlang emulator. Each element of - the list is a tuple <c>{Type, Size}</c>. The first element - <c><anno>Type</anno></c>is an atom describing memory type. The second - element <c><anno>Size</anno></c>is memory size in bytes. A description of - each memory type follows:</p> + <desc> + <p>Returns a list with information about memory + dynamically allocated by the Erlang emulator. Each list + element is a tuple <c>{Type, Size}</c>. The first element + <c><anno>Type</anno></c> is an atom describing memory type. The second + element <c><anno>Size</anno></c> is the memory size in bytes.</p> + <p>The memory types are as follows:</p> <taglist> <tag><c>total</c></tag> <item> - <p>The total amount of memory currently allocated, which is - the same as the sum of memory size for <c>processes</c> + <p>The total amount of memory currently allocated. This is + the same as the sum of the memory size for <c>processes</c> and <c>system</c>.</p> </item> <tag><c>processes</c></tag> <item> - <p>The total amount of memory currently allocated by + <p>The total amount of memory currently allocated for the Erlang processes.</p> </item> <tag><c>processes_used</c></tag> <item> <p>The total amount of memory currently used by the Erlang - processes.</p> - <p>This memory is part of the memory presented as + processes. This is part of the memory presented as <c>processes</c> memory.</p> </item> <tag><c>system</c></tag> <item> - <p>The total amount of memory currently allocated by + <p>The total amount of memory currently allocated for the emulator that is not directly related to any Erlang - process.</p> - <p>Memory presented as <c>processes</c> is not included in - this memory.</p> + process. Memory presented as <c>processes</c> is not + included in this memory.</p> </item> <tag><c>atom</c></tag> <item> - <p>The total amount of memory currently allocated for atoms.</p> - <p>This memory is part of the memory presented as + <p>The total amount of memory currently allocated for atoms. + This memory is part of the memory presented as <c>system</c> memory.</p> </item> <tag><c>atom_used</c></tag> <item> - <p>The total amount of memory currently used for atoms.</p> - <p>This memory is part of the memory presented as + <p>The total amount of memory currently used for atoms. + This memory is part of the memory presented as <c>atom</c> memory.</p> </item> <tag><c>binary</c></tag> <item> <p>The total amount of memory currently allocated for - binaries.</p> - <p>This memory is part of the memory presented as - <c>system</c> memory.</p> + binaries. This memory is part of the memory presented + as <c>system</c> memory.</p> </item> <tag><c>code</c></tag> <item> <p>The total amount of memory currently allocated for - Erlang code.</p> - <p>This memory is part of the memory presented as - <c>system</c> memory.</p> + Erlang code. This memory is part of the memory presented + as <c>system</c> memory.</p> </item> <tag><c>ets</c></tag> <item> <p>The total amount of memory currently allocated for ets - tables.</p> - <p>This memory is part of the memory presented as + tables. This memory is part of the memory presented as <c>system</c> memory.</p> </item> <tag><c>low</c></tag> <item> - <p>Only on 64-bit halfword emulator.</p> - <p>The total amount of memory allocated in low memory areas - that are restricted to less than 4 Gb even though - the system may have more physical memory.</p> - <p>May be removed in future releases of halfword emulator.</p> + <p>Only on 64-bit halfword emulator. + The total amount of memory allocated in low memory areas + that are restricted to less than 4 GB, although + the system can have more memory.</p> + <p>Can be removed in a future release of the halfword + emulator.</p> </item> <tag><c>maximum</c></tag> <item> <p>The maximum total amount of memory allocated since - the emulator was started.</p> - <p>This tuple is only present when the emulator is run with - instrumentation.</p> + the emulator was started. This tuple is only present + when the emulator is run with instrumentation.</p> <p>For information on how to run the emulator with - instrumentation see + instrumentation, see <seealso marker="tools:instrument">instrument(3)</seealso> and/or <seealso marker="erts:erl">erl(1)</seealso>.</p> </item> </taglist> <note> <p>The <c>system</c> value is not complete. Some allocated - memory that should be part of the <c>system</c> value are - not.</p> + memory that is to be part of this value is not.</p> <p>When the emulator is run with instrumentation, the <c>system</c> value is more accurate, but memory - directly allocated by <c>malloc</c> (and friends) are still + directly allocated for <c>malloc</c> (and friends) is still not part of the <c>system</c> value. Direct calls to - <c>malloc</c> are only done from OS specific runtime - libraries and perhaps from user implemented Erlang drivers + <c>malloc</c> are only done from OS-specific runtime + libraries and perhaps from user-implemented Erlang drivers that do not use the memory allocation functions in the driver interface.</p> - <p>Since the <c>total</c> value is the sum of <c>processes</c> - and <c>system</c> the error in <c>system</c> will propagate + <p>As the <c>total</c> value is the sum of <c>processes</c> + and <c>system</c>, the error in <c>system</c> propagates to the <c>total</c> value.</p> <p>The different amounts of memory that are summed are - <em>not</em> gathered atomically which also introduce + <em>not</em> gathered atomically, which introduces an error in the result.</p> </note> - <p>The different values has the following relation to each + <p>The different values have the following relation to each other. Values beginning with an uppercase letter is not part of the result.</p> <code type="none"> @@ -2257,69 +2759,62 @@ os_prompt% </pre> processes = processes_used + ProcessesNotUsed system = atom + binary + code + ets + OtherSystem atom = atom_used + AtomNotUsed - RealTotal = processes + RealSystem RealSystem = system + MissedSystem</code> - <p>More tuples in the returned list may be added in the future.</p> + <p>More tuples in the returned list can be added in a + future release.</p> <note> <p>The <c>total</c> value is supposed to be the total amount of memory dynamically allocated by the emulator. Shared libraries, the code of the emulator itself, and - the emulator stack(s) are not supposed to be included. That + the emulator stacks are not supposed to be included. That is, the <c>total</c> value is <em>not</em> supposed to be - equal to the total size of all pages mapped to the emulator. - Furthermore, due to fragmentation and pre-reservation of - memory areas, the size of the memory segments which contain - the dynamically allocated memory blocks can be substantially + equal to the total size of all pages mapped to the emulator.</p> + <p>Furthermore, because of fragmentation and prereservation of + memory areas, the size of the memory segments containing + the dynamically allocated memory blocks can be much larger than the total size of the dynamically allocated memory blocks.</p> </note> <note> - <p> - Since erts version 5.6.4 <c>erlang:memory/0</c> requires that + <p>As from <c>ERTS</c> 5.6.4, <c>erlang:memory/0</c> requires that all <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso> - allocators are enabled (default behaviour). - </p> + allocators are enabled (default behavior).</p> </note> - <p>Failure:</p> - <taglist> - <tag><c>notsup</c></tag> - <item> - If an <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso> - allocator has been disabled. - </item> - </taglist> + <p>Failure: <c>notsup</c> if an + <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso> + allocator has been disabled.</p> </desc> </func> + <func> <name name="memory" arity="1" clause_i="1"/> <name name="memory" arity="1" clause_i="2"/> + <fsummary>Information about dynamically allocated memory.</fsummary> <type name="memory_type"/> - <fsummary>Information about dynamically allocated memory</fsummary> <desc> <p>Returns the memory size in bytes allocated for memory of type <c><anno>Type</anno></c>. The argument can also be given as a list of <c>memory_type()</c> atoms, in which case a corresponding list of <c>{memory_type(), Size :: integer >= 0}</c> tuples is returned.</p> <note> - <p> - Since erts version 5.6.4 <c>erlang:memory/1</c> requires that + <p>As from <c>ERTS</c> version 5.6.4, + <c>erlang:memory/1</c> requires that all <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso> - allocators are enabled (default behaviour). - </p> + allocators are enabled (default behavior).</p> </note> <p>Failures:</p> <taglist> <tag><c>badarg</c></tag> <item> - If <c><anno>Type</anno></c> is not one of the memory types listed in the - documentation of + If <c><anno>Type</anno></c> is not one of the memory types + listed in the description of <seealso marker="#memory/0">erlang:memory/0</seealso>. </item> <tag><c>badarg</c></tag> <item> - If <c>maximum</c> is passed as <c><anno>Type</anno></c> and the emulator - is not run in instrumented mode. + If <c>maximum</c> is passed as <c><anno>Type</anno></c> and + the emulator is not run in instrumented mode. </item> <tag><c>notsup</c></tag> <item> @@ -2331,226 +2826,367 @@ os_prompt% </pre> <seealso marker="#memory/0">erlang:memory/0</seealso>.</p> </desc> </func> + <func> <name name="min" arity="2"/> - <fsummary>Return the smallest of two term</fsummary> + <fsummary>Returns the smallest of two terms.</fsummary> <desc> - <p>Return the smallest of <c><anno>Term1</anno></c> and <c><anno>Term2</anno></c>; - if the terms compare equal, <c><anno>Term1</anno></c> will be returned.</p> + <p>Returns the smallest of <c><anno>Term1</anno></c> and + <c><anno>Term2</anno></c>. + If the terms are equal, <c><anno>Term1</anno></c> is returned.</p> </desc> </func> + <func> <name name="module_loaded" arity="1"/> - <fsummary>Check if a module is loaded</fsummary> + <fsummary>Checks if a module is loaded.</fsummary> <desc> - <p>Returns <c>true</c> if the module <c><anno>Module</anno></c> is loaded, - otherwise returns <c>false</c>. It does not attempt to load + <p>Returns <c>true</c> if the module <c><anno>Module</anno></c> + is loaded, otherwise <c>false</c>. It does not attempt to load the module.</p> <warning> <p>This BIF is intended for the code server (see - <seealso marker="kernel:code">code(3)</seealso>) and should not be + <seealso marker="kernel:code">code(3)</seealso>) and is not to be used elsewhere.</p> </warning> </desc> </func> + <func> - <name name="monitor" arity="2"/> - <fsummary>Start monitoring</fsummary> - <desc> - <p>The calling process starts monitoring <c><anno>Item</anno></c> which is - an object of type <c><anno>Type</anno></c>.</p> - <p>Currently only processes can be monitored, i.e. the only - allowed <c><anno>Type</anno></c> is <c>process</c>, but other types may be - allowed in the future.</p> - <p><c><anno>Item</anno></c> can be:</p> - <taglist> - <tag><c>pid()</c></tag> - <item> - <p>The pid of the process to monitor.</p> - </item> - <tag><c>{RegName, Node}</c></tag> - <item> - <p>A tuple consisting of a registered name of a process and - a node name. The process residing on the node <c>Node</c> - with the registered name <c>RegName</c> will be monitored.</p> - </item> - <tag><c>RegName</c></tag> - <item> - <p>The process locally registered as <c>RegName</c> will be - monitored.</p> - </item> - </taglist> - <note> - <p>When a process is monitored by registered name, the process - that has the registered name at the time when - <c>monitor/2</c> is called will be monitored. - The monitor will not be effected, if the registered name is - unregistered.</p> - </note> - <p>A <c>'DOWN'</c> message will be sent to the monitoring - process if <c><anno>Item</anno></c> dies, if <c><anno>Item</anno></c> does not exist, - or if the connection is lost to the node which <c><anno>Item</anno></c> - resides on. A <c>'DOWN'</c> message has the following pattern:</p> - <code type="none"> -{'DOWN', MonitorRef, Type, Object, Info}</code> - <p>where <c>MonitorRef</c> and <c>Type</c> are the same as - described above, and:</p> - <taglist> - <tag><c>Object</c></tag> - <item> - <p>A reference to the monitored object:</p> - <list type="bulleted"> - <item>the pid of the monitored process, if <c><anno>Item</anno></c> was - specified as a pid.</item> - <item><c>{RegName, Node}</c>, if <c><anno>Item</anno></c> was specified as - <c>{RegName, Node}</c>.</item> - <item><c>{RegName, Node}</c>, if <c><anno>Item</anno></c> was specified as - <c>RegName</c>. <c>Node</c> will in this case be the - name of the local node (<c>node()</c>).</item> - </list> - </item> - <tag><c>Info</c></tag> - <item> - <p>Either the exit reason of the process, <c>noproc</c> - (non-existing process), or <c>noconnection</c> (no - connection to <c><anno>Node</anno></c>).</p> - </item> - </taglist> - <note> - <p>If/when <c>monitor/2</c> is extended (e.g. to - handle other item types than <c>process</c>), other - possible values for <c>Object</c>, and <c>Info</c> in the - <c>'DOWN'</c> message will be introduced.</p> - </note> - <p>The monitoring is turned off either when the <c>'DOWN'</c> - message is sent, or when - <seealso marker="#demonitor/1">demonitor/1</seealso> - is called.</p> - <p>If an attempt is made to monitor a process on an older node - (where remote process monitoring is not implemented or one - where remote process monitoring by registered name is not - implemented), the call fails with <c>badarg</c>.</p> - <p>Making several calls to <c>monitor/2</c> for the same - <c><anno>Item</anno></c> is not an error; it results in as many, completely - independent, monitorings.</p> + <name name="monitor" arity="2" clause_i="1"/> + <name name="monitor" arity="2" clause_i="2"/> + <fsummary>Starts monitoring.</fsummary> + <type name="registered_name"/> + <type name="registered_process_identifier"/> + <type name="monitor_process_identifier"/> + <desc> + <p>Send a monitor request of type <c><anno>Type</anno></c> to the + entity identified by <c><anno>Item</anno></c>. The caller of + <c>monitor/2</c> will later be notified by a monitor message on the + following format if the monitored state is changed:</p> + <code type="none">{Tag, <anno>MonitorRef</anno>, <anno>Type</anno>, Object, Info}</code> + <note><p>The monitor request is an asynchronous signal. That is, it + takes time before the signal reaches its destination.</p></note> + <p>Valid <c><anno>Type</anno></c>s:</p> + <taglist> + <tag><marker id="monitor_process"/><c>process</c></tag> + <item> + <p>Monitor the existence of the process identified by + <c><anno>Item</anno></c>. Valid + <c><anno>Item</anno></c>s in combination with the + <c>process <anno>Type</anno></c> can be any of the following:</p> + <taglist> + <tag><c>pid()</c></tag> + <item> + <p>The process identifier of the process to monitor.</p> + </item> + <tag><c>{RegisteredName, Node}</c></tag> + <item> + <p>A tuple consisting of a registered name of a process and + a node name. The process residing on the node <c>Node</c> + with the registered name <c>{RegisteredName, Node}</c> will + be monitored.</p> + </item> + <tag><c>RegisteredName</c></tag> + <item> + <p>The process locally registered as <c>RegisteredName</c> + will become monitored.</p> + </item> + </taglist> + <note><p>When a registered name is used, the + process that has the registered name when the + monitor request reach its destination will be monitored. + The monitor is not effected if the registered name is + unregistered, or unregistered and later registered on another + process.</p></note> + <p>The monitor is triggered either when the monitored process + terminates, is non existing, or if the connection to it is + lost. In the case the connection to it is lost, we do not know + if it still exist or not. After this type of monitor has been + triggered, the monitor is automatically removed.</p> + <p>When the monitor is triggered a <c>'DOWN'</c> message is + sent to the monitoring process. A <c>'DOWN'</c> message has + the following pattern:</p> + <code type="none">{'DOWN', MonitorRef, Type, Object, Info}</code> + <p>Here <c>MonitorRef</c> and <c>Type</c> are the same as + described earlier, and:</p> + <taglist> + <tag><c>Object</c></tag> + <item> + <p>equals:</p> + <taglist> + <tag><c><anno>Item</anno></c></tag> + <item>If <c><anno>Item</anno></c> is specified by a + process identifier.</item> + <tag><c>{RegisteredName, Node}</c></tag> + <item>If <c><anno>Item</anno></c> is specified as + <c>RegisteredName</c>, or <c>{RegisteredName, Node}</c> + where <c>Node</c> corresponds to the node that the + monitored process resides on.</item> + </taglist> + </item> + <tag><c>Info</c></tag> + <item> + <p>Either the exit reason of the process, <c>noproc</c> + (non-existing process), or <c>noconnection</c> (no + connection to the node where the monitored process + resides).</p></item> + </taglist> + <p>The monitoring is turned off when the <c>'DOWN'</c> + message is sent or when + <seealso marker="#demonitor/1">demonitor/1</seealso> + is called.</p> + <p>If an attempt is made to monitor a process on an older node + (where remote process monitoring is not implemented or + where remote process monitoring by registered name is not + implemented), the call fails with <c>badarg</c>.</p> + <note> + <p>The format of the <c>'DOWN'</c> message changed in ERTS + version 5.2 (OTP R9B) for monitoring + <em>by registered name</em>. Element <c>Object</c> of + the <c>'DOWN'</c> message could in earlier versions + sometimes be the process identifier of the monitored process and sometimes + be the registered name. Now element <c>Object</c> is + always a tuple consisting of the registered name and + the node name. Processes on new nodes (ERTS version 5.2 + or higher) always get <c>'DOWN'</c> messages on + the new format even if they are monitoring processes on old + nodes. Processes on old nodes always get <c>'DOWN'</c> + messages on the old format.</p> + </note> + </item> + <tag><marker id="monitor_time_offset"/><c>time_offset</c></tag> + <item> + <p>Monitor changes in + <seealso marker="#time_offset/0">time offset</seealso> + between + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso> and + <seealso marker="time_correction#Erlang_System_Time">Erlang + system time</seealso>. There is only one valid + <c><anno>Item</anno></c> in combination with the + <c>time_offset <anno>Type</anno></c>, namely the atom + <c>clock_service</c>. Note that the atom <c>clock_service</c> is + <em>not</em> the registered name of a process. In this specific + case it serves as an identifier of the runtime system internal + clock service at current runtime system instance.</p> + + <p>The monitor is triggered when the time offset is changed. + This either if the time offset value is changed, or if the + offset is changed from preliminary to final during + <seealso marker="#system_flag_time_offset">finalization + of the time offset</seealso> when the + <seealso marker="time_correction#Single_Time_Warp_Mode">single + time warp mode</seealso> is used. When a change from preliminary + to final time offset is made, the monitor will be triggered once + regardless of whether the time offset value was actually changed + or not.</p> + + <p>If the runtime system is in + <seealso marker="time_correction#Multi_Time_Warp_Mode">multi + time warp mode</seealso>, the time offset will be changed when + the runtime system detects that the + <seealso marker="time_correction#OS_System_Time">OS system + time</seealso> has changed. The runtime system will, however, + not detect this immediately when it happens. A task checking + the time offset is scheduled to execute at least once a minute, + so under normal operation this should be detected within a + minute, but during heavy load it might take longer time.</p> + + <p>The monitor will <em>not</em> be automatically removed + after it has been triggered. That is, repeated changes of + the time offset will trigger the monitor repeatedly.</p> + + <p>When the monitor is triggered a <c>'CHANGE'</c> message will + be sent to the monitoring process. A <c>'CHANGE'</c> message has + the following pattern:</p> + <code type="none">{'CHANGE', MonitorRef, Type, Item, NewTimeOffset}</code> + <p>where <c>MonitorRef</c>, <c><anno>Type</anno></c>, and + <c><anno>Item</anno></c> are the same as described above, and + <c>NewTimeOffset</c> is the new time offset.</p> + + <p>When the <c>'CHANGE'</c> message has been received you are + guaranteed not to retrieve the old time offset when calling + <seealso marker="#time_offset/0"><c>erlang:time_offset()</c></seealso>. + Note that you can observe the change of the time offset + when calling <c>erlang:time_offset()</c> before you + get the <c>'CHANGE'</c> message.</p> + + </item> + </taglist> + <p>Making several calls to <c>monitor/2</c> for the same + <c><anno>Item</anno></c> and/or <c><anno>Type</anno></c> is not + an error; it results in as many independent monitoring instances.</p> + <p>The monitor functionality is expected to be extended. That is, + other <c><anno>Type</anno></c>s and <c><anno>Item</anno></c>s + are expected to be supported in a future release.</p> <note> - <p>The format of the <c>'DOWN'</c> message changed in the 5.2 - version of the emulator (OTP release R9B) for monitor <em>by registered name</em>. The <c>Object</c> element of - the <c>'DOWN'</c> message could in earlier versions - sometimes be the pid of the monitored process and sometimes - be the registered name. Now the <c>Object</c> element is - always a tuple consisting of the registered name and - the node name. Processes on new nodes (emulator version 5.2 - or greater) will always get <c>'DOWN'</c> messages on - the new format even if they are monitoring processes on old - nodes. Processes on old nodes will always get <c>'DOWN'</c> - messages on the old format.</p> + <p>If or when <c>monitor/2</c> is extended, other + possible values for <c>Tag</c>, <c>Object</c> and + <c>Info</c> in the monitor message will be introduced.</p> </note> </desc> </func> + <func> <name name="monitor_node" arity="2"/> - <fsummary>Monitor the status of a node</fsummary> + <fsummary>Monitors the status of a node.</fsummary> <desc> - <p>Monitors the status of the node <c><anno>Node</anno></c>. If <c><anno>Flag</anno></c> - is <c>true</c>, monitoring is turned on; if <c><anno>Flag</anno></c> is - <c>false</c>, monitoring is turned off.</p> + <p>Monitors the status of the node <c><anno>Node</anno></c>. + If <c><anno>Flag</anno></c> + is <c>true</c>, monitoring is turned on. If <c><anno>Flag</anno></c> + is <c>false</c>, monitoring is turned off.</p> <p>Making several calls to <c>monitor_node(Node, true)</c> for - the same <c><anno>Node</anno></c> is not an error; it results in as many, - completely independent, monitorings.</p> + the same <c><anno>Node</anno></c> is not an error; it results + in as many independent monitoring instances.</p> <p>If <c><anno>Node</anno></c> fails or does not exist, the message <c>{nodedown, Node}</c> is delivered to the process. If a process has made two calls to <c>monitor_node(Node, true)</c> - and <c><anno>Node</anno></c> terminates, two <c>nodedown</c> messages are - delivered to the process. If there is no connection to - <c><anno>Node</anno></c>, there will be an attempt to create one. If this - fails, a <c>nodedown</c> message is delivered.</p> + and <c><anno>Node</anno></c> terminates, two <c>nodedown</c> messages + are delivered to the process. If there is no connection to + <c><anno>Node</anno></c>, an attempt is made to create one. + If this fails, a <c>nodedown</c> message is delivered.</p> <p>Nodes connected through hidden connections can be monitored - as any other node.</p> + as any other nodes.</p> <p>Failure: <c>badarg</c> if the local node is not alive.</p> </desc> </func> + <func> <name name="monitor_node" arity="3"/> - <fsummary>Monitor the status of a node</fsummary> + <fsummary>Monitors the status of a node.</fsummary> <desc> - <p>Behaves as <c>monitor_node/2</c> except that it allows an + <p>Behaves as + <seealso marker="#monitor_node/2">monitor_node/2</seealso> + except that it allows an extra option to be given, namely <c>allow_passive_connect</c>. - The option allows the BIF to wait the normal net connection - timeout for the <em>monitored node</em> to connect itself, + This option allows the BIF to wait the normal network connection + time-out for the <em>monitored node</em> to connect itself, even if it cannot be actively connected from this node - (i.e. it is blocked). The state where this might be useful can - only be achieved by using the kernel option - <c>dist_auto_connect once</c>. If that kernel option is not - used, the <c>allow_passive_connect</c> option has no - effect.</p> + (that is, it is blocked). The state where this can be useful + can only be achieved by using the <c>Kernel</c> option + <c>dist_auto_connect once</c>. If that option is not + used, option <c>allow_passive_connect</c> has no effect.</p> <note> - <p>The <c>allow_passive_connect</c> option is used + <p>Option <c>allow_passive_connect</c> is used internally and is seldom needed in applications where the - network topology and the kernel options in effect is known in - advance.</p> + network topology and the <c>Kernel</c> options in effect + are known in advance.</p> </note> <p>Failure: <c>badarg</c> if the local node is not alive or the option list is malformed.</p> </desc> </func> + + <func> + <name name="monotonic_time" arity="0"/> + <fsummary>Current Erlang monotonic time.</fsummary> + <desc> + <p>Returns the current + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso> in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso>. This + is a monotonically increasing time since some unspecified point in + time.</p> + + <note><p>This is a + <seealso marker="time_correction#Monotonically_Increasing">monotonically increasing</seealso> time, but <em>not</em> a + <seealso marker="time_correction#Strictly_Monotonically_Increasing">strictly monotonically increasing</seealso> + time. That is, consecutive calls to + <c>erlang:monotonic_time/0</c> can produce the same result.</p> + + <p>Different runtime system instances will use different + unspecified points in time as base for their Erlang monotonic clocks. + That is, it is <em>pointless</em> comparing monotonic times from + different runtime system instances. Different runtime system instances + may also place this unspecified point in time different relative + runtime system start. It may be placed in the future (time at start + is a negative value), the past (time at start is a + positive value), or the runtime system start (time at start is + zero). The monotonic time at runtime system start can be + retrieved by calling + <seealso marker="#system_info_start_time"><c>erlang:system_info(start_time)</c></seealso>.</p></note> + </desc> + </func> + <func> + <name name="monotonic_time" arity="1"/> + <fsummary>Current Erlang monotonic time</fsummary> + <desc> + <p>Returns the current + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso> converted + into the <c><anno>Unit</anno></c> passed as argument.</p> + + <p>Same as calling + <seealso marker="#convert_time_unit/3"><c>erlang:convert_time_unit</c></seealso><c>(</c><seealso marker="#monotonic_time/0"><c>erlang:monotonic_time()</c></seealso><c>, + native, <anno>Unit</anno>)</c> + however optimized for commonly used <c><anno>Unit</anno></c>s.</p> + </desc> + </func> <func> <name name="nif_error" arity="1"/> - <fsummary>Stop execution with a given reason</fsummary> + <fsummary>Stops execution with a given reason.</fsummary> <desc> <p>Works exactly like - <seealso marker="#error/1">erlang:error/1</seealso>, - but Dialyzer thinks that this BIF will return an arbitrary term. - When used in a stub function for a NIF to generate an - exception when the NIF library is not loaded, Dialyzer - will not generate false warnings.</p> + <seealso marker="#error/1">erlang:error/1</seealso>, but + <c>Dialyzer</c> thinks that this BIF will return an arbitrary + term. When used in a stub function for a NIF to generate an + exception when the NIF library is not loaded, <c>Dialyzer</c> + does not generate false warnings.</p> </desc> </func> + <func> <name name="nif_error" arity="2"/> - <fsummary>Stop execution with a given reason</fsummary> + <fsummary>Stops execution with a given reason.</fsummary> <desc> <p>Works exactly like - <seealso marker="#error/2">erlang:error/2</seealso>, - but Dialyzer thinks that this BIF will return an arbitrary term. - When used in a stub function for a NIF to generate an - exception when the NIF library is not loaded, Dialyzer - will not generate false warnings.</p> + <seealso marker="#error/2">erlang:error/2</seealso>, but + <c>Dialyzer</c> thinks that this BIF will return an arbitrary + term. When used in a stub function for a NIF to generate an + exception when the NIF library is not loaded, <c>Dialyzer</c> + does not generate false warnings.</p> </desc> </func> + <func> <name name="node" arity="0"/> - <fsummary>Name of the local node</fsummary> + <fsummary>Name of the local node.</fsummary> <desc> <p>Returns the name of the local node. If the node is not alive, <c>nonode@nohost</c> is returned instead.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="node" arity="1"/> - <fsummary>At which node is a pid, port or reference located</fsummary> + <fsummary>At which node a pid, port, or reference originates.</fsummary> <desc> - <p>Returns the node where <c><anno>Arg</anno></c> is located. <c><anno>Arg</anno></c> can - be a pid, a reference, or a port. If the local node is not + <p>Returns the node where <c><anno>Arg</anno></c> originates. + <c><anno>Arg</anno></c> can + be a process identifier, a reference, or a port. + If the local node is not alive, <c>nonode@nohost</c> is returned.</p> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="nodes" arity="0"/> - <fsummary>All visible nodes in the system</fsummary> + <fsummary>All visible nodes in the system.</fsummary> <desc> - <p>Returns a list of all visible nodes in the system, excluding + <p>Returns a list of all visible nodes in the system, except the local node. Same as <c>nodes(visible)</c>.</p> </desc> </func> + <func> <name name="nodes" arity="1"/> - <fsummary>All nodes of a certain type in the system</fsummary> + <fsummary>All nodes of a certain type in the system.</fsummary> <desc> - <p>Returns a list of nodes according to argument given. - The result returned when the argument is a list, is the list + <p>Returns a list of nodes according to the argument given. + The returned result when the argument is a list, is the list of nodes satisfying the disjunction(s) of the list elements.</p> <p><c><anno>NodeType</anno></c> can be any of the following:</p> <taglist> @@ -2572,128 +3208,131 @@ os_prompt% </pre> </item> <tag><c>known</c></tag> <item> - <p>Nodes which are known to this node, i.e., connected, - previously connected, etc.</p> + <p>Nodes that are known to this node. That is, connected + nodes and nodes referred to by process identifiers, port + identifiers and references located on this node. + The set of known nodes is garbage collected. Notice that + this garbage collection can be delayed. For more + information, see + <seealso marker="erlang#system_info_delayed_node_table_gc">delayed_node_table_gc</seealso>. + </p> </item> </taglist> <p>Some equalities: <c>[node()] = nodes(this)</c>, <c>nodes(connected) = nodes([visible, hidden])</c>, and <c>nodes() = nodes(visible)</c>.</p> - <p>If the local node is not alive, - <c>nodes(this) == nodes(known) == [nonode@nohost]</c>, for - any other <c><anno>Arg</anno></c> the empty list [] is returned.</p> </desc> </func> + <func> <name name="now" arity="0"/> + <fsummary>Elapsed time since 00:00 GMT.</fsummary> <type name="timestamp"/> - <fsummary>Elapsed time since 00:00 GMT</fsummary> <desc> + <warning><p><em>This function is deprecated! Do not use it!</em> + See the users guide chapter + <seealso marker="time_correction">Time and Time Correction</seealso> + for more information. Specifically the + <seealso marker="time_correction#Dos_and_Donts">Dos and Dont's</seealso> + section for information on what to use instead of <c>erlang:now/0</c>. + </p></warning> <p>Returns the tuple <c>{MegaSecs, Secs, MicroSecs}</c> which is - the elapsed time since 00:00 GMT, January 1, 1970 (zero hour) + the elapsed time since 00:00 GMT, January 1, 1970 (zero hour), on the assumption that the underlying OS supports this. - Otherwise, some other point in time is chosen. It is also - guaranteed that subsequent calls to this BIF returns + Otherwise some other point in time is chosen. It is also + guaranteed that subsequent calls to this BIF return continuously increasing values. Hence, the return value from - <c>now()</c> can be used to generate unique time-stamps, - and if it is called in a tight loop on a fast machine + <c>now()</c> can be used to generate unique time-stamps. + If it is called in a tight loop on a fast machine, the time of the node can become skewed.</p> - <p>It can only be used to check the local time of day if - the time-zone info of the underlying operating system is + <p>Can only be used to check the local time of day if + the time-zone information of the underlying OS is properly configured.</p> - <p>If you do not need the return value to be unique and - monotonically increasing, use - <seealso marker="kernel:os#timestamp/0">os:timestamp/0</seealso> - instead to avoid some overhead.</p> </desc> </func> + <func> <name name="open_port" arity="2"/> - <fsummary>Open a port</fsummary> + <fsummary>Opens a port.</fsummary> <desc> <p>Returns a port identifier as the result of opening a new Erlang port. A port can be seen as an external Erlang - process. <c><anno>PortName</anno></c> is one of the following:</p> + process.</p> + <p>The name of the executable as well as the arguments + given in <c>cd</c>, <c>env</c>, <c>args</c>, and <c>arg0</c> are + subject to Unicode file name translation if the system is running + in Unicode file name mode. To avoid + translation or to force, for example UTF-8, supply the executable + and/or arguments as a binary in the correct + encoding. For details, see the module + <seealso marker="kernel:file">file</seealso>, the function + <seealso marker="kernel:file#native_name_encoding/0">file:native_name_encoding/0</seealso>, and the + <seealso marker="stdlib:unicode_usage">STDLIB </seealso> + User's Guide.</p> + <note><p>The characters in the name (if given as a list) can + only be higher than 255 if the Erlang Virtual Machine is started + in Unicode file name translation mode. Otherwise the name + of the executable is limited to the ISO-latin-1 + character set.</p></note> + <p><c><anno>PortName</anno></c> can be any of the following:</p> <taglist> <tag><c>{spawn, <anno>Command</anno>}</c></tag> <item> - <p>Starts an external program. <c><anno>Command</anno></c> is the name - of the external program which will be run. <c><anno>Command</anno></c> + <p>Starts an external program. <c><anno>Command</anno></c> + is the name of the external program to be run. + <c><anno>Command</anno></c> runs outside the Erlang work space unless an Erlang - driver with the name <c><anno>Command</anno></c> is found. If found, - that driver will be started. A driver runs in the Erlang - workspace, which means that it is linked with the Erlang + driver with the name <c><anno>Command</anno></c> is found. + If found, that driver is started. A driver runs in the Erlang + work space, which means that it is linked with the Erlang runtime system.</p> <p>When starting external programs on Solaris, the system call <c>vfork</c> is used in preference to <c>fork</c> for performance reasons, although it has a history of - being less robust. If there are problems with using - <c>vfork</c>, setting the environment variable - <c>ERL_NO_VFORK</c> to any value will cause <c>fork</c> + being less robust. If there are problems using + <c>vfork</c>, setting environment variable + <c>ERL_NO_VFORK</c> to any value causes <c>fork</c> to be used instead.</p> - - <p>For external programs, the <c>PATH</c> is searched + <p>For external programs, <c>PATH</c> is searched (or an equivalent method is used to find programs, - depending on operating system). This is done by invoking - the shell on certain platforms. The first space - separated token of the command will be considered as the + depending on OS). This is done by invoking + the shell on certain platforms. The first space-separated + token of the command is considered as the name of the executable (or driver). This (among other things) makes this option unsuitable for running - programs having spaces in file or directory names. Use - {spawn_executable, <anno>Command</anno>} instead if spaces in executable - file names is desired.</p> + programs having spaces in file names or directory names. + If spaces in executable file names are desired, use + <c>{spawn_executable, <anno>Command</anno>}</c> instead.</p> </item> <tag><c>{spawn_driver, <anno>Command</anno>}</c></tag> <item> <p>Works like <c>{spawn, <anno>Command</anno>}</c>, but demands the - first (space separated) token of the command to be the name of a + first (space-separated) token of the command to be the name of a loaded driver. If no driver with that name is loaded, a <c>badarg</c> error is raised.</p> </item> <tag><c>{spawn_executable, <anno>FileName</anno>}</c></tag> <item> - <p>Works like <c>{spawn, <anno>FileName</anno>}</c>, but only runs - external executables. The <c><anno>FileName</anno></c> in its whole - is used as the name of the executable, including any - spaces. If arguments are to be passed, the - <c>args</c> and <c>arg0</c> <c><anno>PortSettings</anno></c> can be used.</p> - - <p>The shell is not usually invoked to start the - program, it's executed directly. Neither is the - <c>PATH</c> (or equivalent) searched. To find a program - in the PATH to execute, use <seealso - marker="kernel:os#find_executable/1">os:find_executable/1</seealso>.</p> + external executables. <c><anno>FileName</anno></c> in its whole + is used as the name of the executable, including any spaces. + If arguments are to be passed, the <c><anno>PortSettings</anno></c> + <c>args</c> and <c>arg0</c> can be used.</p> + <p>The shell is usually not invoked to start the + program, it is executed directly. <c>PATH</c> (or + equivalent) is not searched. To find a program + in <c>PATH</c> to execute, use + <seealso marker="kernel:os#find_executable/1">os:find_executable/1</seealso>.</p> <p>Only if a shell script or <c>.bat</c> file is - executed, the appropriate command interpreter will - implicitly be invoked, but there will still be no - command argument expansion or implicit PATH search.</p> - - <p>The name of the executable as well as the arguments - given in <c>args</c> and <c>arg0</c> is subject to - Unicode file name translation if the system is running - in Unicode file name mode. To avoid - translation or force i.e. UTF-8, supply the executable - and/or arguments as a binary in the correct - encoding. See the <seealso - marker="kernel:file">file</seealso> module, the - <seealso marker="kernel:file#native_name_encoding/0"> - file:native_name_encoding/0</seealso> function and the - <seealso marker="stdlib:unicode_usage">stdlib users guide - </seealso> for details.</p> - - <note><p>The characters in the name (if given as a list) - can only be > 255 if the Erlang VM is started in - Unicode file name translation mode, otherwise the name - of the executable is limited to the ISO-latin-1 - character set.</p></note> - - <p>If the <c><anno>FileName</anno></c> cannot be run, an error - exception, with the posix error code as the reason, is - raised. The error reason may differ between operating - systems. Typically the error <c>enoent</c> is raised - when one tries to run a program that is not found and - <c>eaccess</c> is raised when the given file is not + executed, the appropriate command interpreter is + invoked implicitly, but there is still no + command argument expansion or implicit <c>PATH</c> search.</p> + <p>If <c><anno>FileName</anno></c> cannot be run, an error + exception is raised, with the POSIX error code as the reason. + The error reason can differ between OSs. + Typically the error <c>enoent</c> is raised when an + attempt is made to run a program that is not found and + <c>eacces</c> is raised when the given file is not executable.</p> </item> <tag><c>{fd, <anno>In</anno>, <anno>Out</anno>}</c></tag> @@ -2702,19 +3341,18 @@ os_prompt% </pre> file descriptors used by Erlang. The file descriptor <c><anno>In</anno></c> can be used for standard input, and the file descriptor <c><anno>Out</anno></c> for standard output. It is only - used for various servers in the Erlang operating system - (<c>shell</c> and <c>user</c>). Hence, its use is very - limited.</p> + used for various servers in the Erlang OS (<c>shell</c> + and <c>user</c>). Hence, its use is limited.</p> </item> </taglist> <p><c><anno>PortSettings</anno></c> is a list of settings for the port. - Valid settings are:</p> + The valid settings are as follows:</p> <taglist> <tag><c>{packet, <anno>N</anno>}</c></tag> <item> <p>Messages are preceded by their length, sent in <c><anno>N</anno></c> - bytes, with the most significant byte first. Valid values - for <c>N</c> are 1, 2, or 4.</p> + bytes, with the most significant byte first. The valid values + for <c>N</c> are 1, 2, and 4.</p> </item> <tag><c>stream</c></tag> <item> @@ -2725,138 +3363,108 @@ os_prompt% </pre> <tag><c>{line, <anno>L</anno>}</c></tag> <item> <p>Messages are delivered on a per line basis. Each line - (delimited by the OS-dependent newline sequence) is - delivered in one single message. The message data format - is <c>{Flag, Line}</c>, where <c>Flag</c> is either - <c>eol</c> or <c>noeol</c> and <c>Line</c> is the actual - data delivered (without the newline sequence).</p> + (delimited by the OS-dependent new line sequence) is + delivered in a single message. The message data format + is <c>{Flag, Line}</c>, where <c>Flag</c> is + <c>eol</c> or <c>noeol</c>, and <c>Line</c> is the + data delivered (without the new line sequence).</p> <p><c><anno>L</anno></c> specifies the maximum line length in bytes. - Lines longer than this will be delivered in more than one - message, with the <c>Flag</c> set to <c>noeol</c> for all + Lines longer than this are delivered in more than one + message, with <c>Flag</c> set to <c>noeol</c> for all but the last message. If end of file is encountered - anywhere else than immediately following a newline - sequence, the last line will also be delivered with - the <c>Flag</c> set to <c>noeol</c>. In all other cases, + anywhere else than immediately following a new line + sequence, the last line is also delivered with + <c>Flag</c> set to <c>noeol</c>. Otherwise lines are delivered with <c>Flag</c> set to <c>eol</c>.</p> - <p>The <c>{packet, <anno>N</anno>}</c> and <c>{line, <anno>L</anno>}</c> settings are - mutually exclusive.</p> + <p>The <c>{packet, <anno>N</anno>}</c> and <c>{line, + <anno>L</anno>}</c> settings are mutually exclusive.</p> </item> <tag><c>{cd, <anno>Dir</anno>}</c></tag> <item> - <p>This is only valid for <c>{spawn, <anno>Command</anno>}</c> and - <c>{spawn_executable, <anno>FileName</anno>}</c>. + <p>Only valid for <c>{spawn, <anno>Command</anno>}</c> and + <c>{spawn_executable, <anno>FileName</anno>}</c>. The external program starts using <c><anno>Dir</anno></c> as its - working directory. <c><anno>Dir</anno></c> must be a string. - </p> + working directory. <c><anno>Dir</anno></c> must be a string.</p> </item> <tag><c>{env, <anno>Env</anno>}</c></tag> <item> - <p>This is only valid for <c>{spawn, <anno>Command</anno>}</c> and + <p>Only valid for <c>{spawn, <anno>Command</anno>}</c> and <c>{spawn_executable, <anno>FileName</anno>}</c>. The environment of the started process is extended using the environment specifications in <c><anno>Env</anno></c>.</p> - <p><c><anno>Env</anno></c> should be a list of tuples <c>{<anno>Name</anno>, <anno>Val</anno>}</c>, - where <c><anno>Name</anno></c> is the name of an environment variable, - and <c><anno>Val</anno></c> is the value it is to have in the spawned - port process. Both <c><anno>Name</anno></c> and <c><anno>Val</anno></c> must be - strings. The one exception is <c><anno>Val</anno></c> being the atom + <p><c><anno>Env</anno></c> is to be a list of tuples + <c>{<anno>Name</anno>, <anno>Val</anno>}</c>, + where <c><anno>Name</anno></c> is the name of an + environment variable, and <c><anno>Val</anno></c> is the + value it is to have in the spawned + port process. Both <c><anno>Name</anno></c> and + <c><anno>Val</anno></c> must be strings. The one + exception is <c><anno>Val</anno></c> being the atom <c>false</c> (in analogy with <c>os:getenv/1</c>), which - removes the environment variable. - </p> - <p>If Unicode filename encoding is in effect (see the <seealso - marker="erts:erl#file_name_encoding">erl manual - page</seealso>), the strings (both <c>Name</c> and - <c>Value</c>) may contain characters with codepoints > 255.</p> + removes the environment variable.</p> </item> <tag><c>{args, [ string() | binary() ]}</c></tag> <item> - - <p>This option is only valid for <c>{spawn_executable, <anno>FileName</anno>}</c> + <p>Only valid for <c>{spawn_executable, <anno>FileName</anno>}</c> and specifies arguments to the executable. Each argument is given as a separate string and (on Unix) eventually ends up as one element each in the argument vector. On - other platforms, similar behavior is mimicked.</p> - - <p>The arguments are not expanded by the shell prior to - being supplied to the executable, most notably this - means that file wildcard expansion will not happen. Use - <seealso - marker="stdlib:filelib#wildcard/1">filelib:wildcard/1</seealso> - to expand wildcards for the arguments. Note that even if + other platforms, a similar behavior is mimicked.</p> + <p>The arguments are not expanded by the shell before + being supplied to the executable. Most notably this + means that file wild card expansion does not happen. + To expand wild cards for the arguments, use + <seealso marker="stdlib:filelib#wildcard/1">filelib:wildcard/1</seealso>. + Notice that even if the program is a Unix shell script, meaning that the - shell will ultimately be invoked, wildcard expansion - will not happen and the script will be provided with the - untouched arguments. On Windows®, wildcard expansion - is always up to the program itself, why this isn't an - issue.</p> - - <p>Note also that the actual executable name (a.k.a. <c>argv[0]</c>) - should not be given in this list. The proper executable name will - automatically be used as argv[0] where applicable.</p> - - <p>When the Erlang VM is running in Unicode file name - mode, the arguments can contain any Unicode characters and - will be translated into whatever is appropriate on the - underlying OS, which means UTF-8 for all platforms except - Windows, which has other (more transparent) ways of - dealing with Unicode arguments to programs. To avoid - Unicode translation of arguments, they can be supplied as - binaries in whatever encoding is deemed appropriate.</p> - - <note><p>The characters in the arguments (if given as a - list of characters) can only be > 255 if the Erlang - VM is started in Unicode file name mode, - otherwise the arguments are limited to the - ISO-latin-1 character set.</p></note> - - <p>If one, for any reason, wants to explicitly set the - program name in the argument vector, the <c>arg0</c> - option can be used.</p> - + shell ultimately is invoked, wild card expansion + does not happen, and the script is provided with the + untouched arguments. On Windows, wild card expansion + is always up to the program itself, therefore this is + not an issue issue.</p> + <p>The executable name (also known as <c>argv[0]</c>) + is not to be given in this list. The proper executable name + is automatically used as argv[0], where applicable.</p> + <p>If you explicitly want to set the + program name in the argument vector, option <c>arg0</c> + can be used.</p> </item> <tag><c>{arg0, string() | binary()}</c></tag> <item> - - <p>This option is only valid for <c>{spawn_executable, <anno>FileName</anno>}</c> + <p>Only valid for <c>{spawn_executable, <anno>FileName</anno>}</c> and explicitly specifies the program name argument when - running an executable. This might in some circumstances, - on some operating systems, be desirable. How the program - responds to this is highly system dependent and no specific + running an executable. This can in some circumstances, + on some OSs, be desirable. How the program + responds to this is highly system-dependent and no specific effect is guaranteed.</p> - - <p>The unicode file name translation rules of the - <c>args</c> option apply to this option as well.</p> - </item> - <tag><c>exit_status</c></tag> <item> - <p>This is only valid for <c>{spawn, <anno>Command</anno>}</c> where - <c><anno>Command</anno></c> refers to an external program, and for - <c>{spawn_executable, <anno>FileName</anno>}</c>.</p> + <p>Only valid for <c>{spawn, <anno>Command</anno>}</c>, where + <c><anno>Command</anno></c> refers to an external program, and + for <c>{spawn_executable, <anno>FileName</anno>}</c>.</p> <p>When the external process connected to the port exits, a message of the form <c>{Port,{exit_status,Status}}</c> is sent to the connected process, where <c>Status</c> is the exit status of the external process. If the program - aborts, on Unix the same convention is used as the shells - do (i.e., 128+signal).</p> - <p>If the <c>eof</c> option has been given as well, - the <c>eof</c> message and the <c>exit_status</c> message - appear in an unspecified order.</p> - <p>If the port program closes its stdout without exiting, - the <c>exit_status</c> option will not work.</p> + aborts on Unix, the same convention is used as the shells + do (that is, 128+signal).</p> + <p>If option <c>eof</c> is also given, the messages <c>eof</c> + and <c>exit_status</c> appear in an unspecified order.</p> + <p>If the port program closes its <c>stdout</c> without exiting, + option <c>exit_status</c> does not work.</p> </item> <tag><c>use_stdio</c></tag> <item> - <p>This is only valid for <c>{spawn, <anno>Command</anno>}</c> and + <p>Only valid for <c>{spawn, <anno>Command</anno>}</c> and <c>{spawn_executable, <anno>FileName</anno>}</c>. It allows the standard input and output (file descriptors 0 - and 1) of the spawned (UNIX) process for communication + and 1) of the spawned (Unix) process for communication with Erlang.</p> </item> <tag><c>nouse_stdio</c></tag> <item> - <p>The opposite of <c>use_stdio</c>. Uses file descriptors + <p>The opposite of <c>use_stdio</c>. It uses file descriptors 3 and 4 for communication with Erlang.</p> </item> <tag><c>stderr_to_stdout</c></tag> @@ -2868,14 +3476,15 @@ os_prompt% </pre> </item> <tag><c>overlapped_io</c></tag> <item> - <p>Affects ports to external programs on Windows® only. - The standard input and standard output handles of the port program - will, if this option is supplied, be opened with the flag - FILE_FLAG_OVERLAPPED, so that the port program can (and has to) do + <p>Affects ports to external programs on Windows only. The + standard input and standard output handles of the port program + are, if this option is supplied, opened with flag + <c>FILE_FLAG_OVERLAPPED</c>, so that the port program can + (and must) do overlapped I/O on its standard handles. This is not normally the case for simple port programs, but an option of value for the - experienced Windows programmer. <em>On all other platforms, this - option is silently discarded</em>.</p> + experienced Windows programmer. <em>On all other platforms, this + option is silently discarded.</em></p> </item> <tag><c>in</c></tag> <item> @@ -2887,345 +3496,354 @@ os_prompt% </pre> </item> <tag><c>binary</c></tag> <item> - <p>All IO from the port are binary data objects as opposed + <p>All I/O from the port is binary data objects as opposed to lists of bytes.</p> </item> <tag><c>eof</c></tag> <item> - <p>The port will not be closed at the end of the file and - produce an exit signal. Instead, it will remain open and - a <c>{Port, eof}</c> message will be sent to the process + <p>The port is not closed at the end of the file and does not + produce an exit signal. Instead, it remains open and + a <c>{Port, eof}</c> message is sent to the process holding the port.</p> </item> <tag><c>hide</c></tag> <item> - <p>When running on Windows, suppress creation of a new + <p>When running on Windows, suppresses creation of a new console window when spawning the port program. (This option has no effect on other platforms.)</p> </item> - <tag><marker id="open_port_parallelism"><c>{parallelism, Boolean}</c></marker></tag> + <tag><c>{parallelism, Boolean}</c></tag> <item> - <p>Set scheduler hint for port parallelism. If set to <c>true</c>, - the VM will schedule port tasks when it by this can improve the - parallelism in the system. If set to <c>false</c>, the VM will - try to perform port tasks immediately and by this improving the - latency at the expense of parallelism. The default can be set on - system startup by passing the - <seealso marker="erl#+spp">+spp</seealso> command line argument - to <seealso marker="erl">erl(1)</seealso>. - </p> + <marker id="open_port_parallelism"></marker> + <p>Sets scheduler hint for port parallelism. If set to + <c>true</c>, the Virtual Machine schedules port tasks; + when doing so, it improves parallelism in the system. If set + to <c>false</c>, the Virtual Machine tries to + perform port tasks immediately, improving latency at the + expense of parallelism. The default can be set at system startup + by passing command-line argument + <seealso marker="erl#+spp">+spp</seealso> to <c>erl(1)</c>.</p> </item> </taglist> - <p>The default is <c>stream</c> for all types of port and + <p>Default is <c>stream</c> for all port types and <c>use_stdio</c> for spawned ports.</p> <p>Failure: If the port cannot be opened, the exit reason is - <c>badarg</c>, <c>system_limit</c>, or the Posix error code which - most closely describes the error, or <c>einval</c> if no Posix code - is appropriate:</p> + <c>badarg</c>, <c>system_limit</c>, or the POSIX error code that + most closely describes the error, or <c>einval</c> if no POSIX + code is appropriate:</p> <taglist> <tag><c>badarg</c></tag> - <item> - <p>Bad input arguments to <c>open_port</c>.</p> + <item>Bad input arguments to <c>open_port</c>. </item> <tag><c>system_limit</c></tag> - <item> - <p>All available ports in the Erlang emulator are in use.</p> + <item>All available ports in the Erlang emulator are in use. </item> <tag><c>enomem</c></tag> - <item> - <p>There was not enough memory to create the port.</p> + <item>Not enough memory to create the port. </item> <tag><c>eagain</c></tag> - <item> - <p>There are no more available operating system processes.</p> + <item>No more available OS processes. </item> <tag><c>enametoolong</c></tag> - <item> - <p>The external command given was too long.</p> + <item>Too long external command. </item> <tag><c>emfile</c></tag> - <item> - <p>There are no more available file descriptors (for the operating system process - that the Erlang emulator runs in).</p> + <item>No more available file descriptors (for the + OS process that the Erlang emulator runs in). </item> <tag><c>enfile</c></tag> - <item> - <p>The file table is full (for the entire operating system).</p> + <item>Full file table (for the entire OS). </item> <tag><c>eacces</c></tag> - <item> - <p>The <c>Command</c> given in <c>{spawn_executable, Command}</c> does not point out an executable file.</p> + <item><c>Command</c> given in <c>{spawn_executable, Command}</c> + does not point out an executable file. </item> <tag><c>enoent</c></tag> - <item> - <p>The <c><anno>FileName</anno></c> given in <c>{spawn_executable, <anno>FileName</anno>}</c> does not point out an existing file.</p> + <item><c><anno>FileName</anno></c> given in + <c>{spawn_executable, <anno>FileName</anno>}</c> + does not point out an existing file. </item> </taglist> <p>During use of a port opened using <c>{spawn, Name}</c>, - <c>{spawn_driver, Name}</c> or <c>{spawn_executable, Name}</c>, + <c>{spawn_driver, Name}</c>, or <c>{spawn_executable, Name}</c>, errors arising when sending messages to it are reported to the owning process using signals of the form - <c>{'EXIT', Port, PosixCode}</c>. See <c>file(3)</c> for - possible values of <c>PosixCode</c>.</p> + <c>{'EXIT', Port, PosixCode}</c>. For the possible values of + <c>PosixCode</c>, see the + <seealso marker="kernel:file">file(3)</seealso> + manual page in <c>Kernel</c>.</p> <p>The maximum number of ports that can be open at the same - time can be configured by passing the - <seealso marker="erl#max_ports"><c>+Q</c></seealso> - command line flag to - <seealso marker="erl"><c>erl(1)</c></seealso>.</p> + time can be configured by passing command-line flag + <seealso marker="erl#max_ports"><c>+Q</c></seealso> to + <c>erl(1)</c>.</p> </desc> </func> + <func> <name name="phash" arity="2"/> + <fsummary>Portable hash function.</fsummary> <type_desc variable="Range">Range = 1..2^32, Hash = 1..Range</type_desc> - <fsummary>Portable hash function</fsummary> <desc> - <p>Portable hash function that will give the same hash for + <p>Portable hash function that gives the same hash for the same Erlang term regardless of machine architecture and - ERTS version (the BIF was introduced in ERTS 4.9.1.1). Range - can be between 1 and 2^32, the function returns a hash value - for <c><anno>Term</anno></c> within the range <c>1..<anno>Range</anno></c>.</p> - <p>This BIF could be used instead of the old deprecated - <c>erlang:hash/2</c> BIF, as it calculates better hashes for - all data-types, but consider using <c>phash2/1,2</c> instead.</p> + <c>ERTS</c> version (the BIF was introduced in <c>ERTS</c> 4.9.1.1). + The function returns a hash value for + <c><anno>Term</anno></c> within the range + <c>1..<anno>Range</anno></c>. The maximum value for + <c><anno>Range</anno></c> is 2^32.</p> + <p>This BIF can be used instead of the old deprecated BIF + <c>erlang:hash/2</c>, as it calculates better hashes for + all data types, but consider using <c>phash2/1,2</c> instead.</p> </desc> </func> + <func> <name name="phash2" arity="1"/> <name name="phash2" arity="2"/> + <fsummary>Portable hash function.</fsummary> <type_desc variable="Range">1..2^32</type_desc> <type_desc variable="Hash">0..Range-1</type_desc> - <fsummary>Portable hash function</fsummary> <desc> - <p>Portable hash function that will give the same hash for + <p>Portable hash function that gives the same hash for the same Erlang term regardless of machine architecture and - ERTS version (the BIF was introduced in ERTS 5.2). Range can - be between 1 and 2^32, the function returns a hash value for - <c><anno>Term</anno></c> within the range <c>0..<anno>Range</anno>-1</c>. When called - without the <c><anno>Range</anno></c> argument, a value in the range - <c>0..2^27-1</c> is returned.</p> - <p>This BIF should always be used for hashing terms. It + <c>ERTS</c> version (the BIF was introduced in <c>ERTS</c> 5.2). + The function returns a hash value for + <c><anno>Term</anno></c> within the range + <c>0..<anno>Range</anno>-1</c>. The maximum value for + <c><anno>Range</anno></c> is 2^32. When without argument + <c><anno>Range</anno></c>, a value in the range + 0..2^27-1 is returned.</p> + <p>This BIF is always to be used for hashing terms. It distributes small integers better than <c>phash/2</c>, and it is faster for bignums and binaries.</p> - <p>Note that the range <c>0..<anno>Range</anno>-1</c> is different from - the range of <c>phash/2</c> (<c>1..<anno>Range</anno></c>).</p> + <p>Notice that the range <c>0..<anno>Range</anno>-1</c> is + different from the range of <c>phash/2</c>, which is + <c>1..<anno>Range</anno></c>.</p> </desc> </func> + <func> <name name="pid_to_list" arity="1"/> - <fsummary>Text representation of a pid</fsummary> + <fsummary>Text representation of a pid.</fsummary> <desc> - <p>Returns a string which corresponds to the text + <p>Returns a string corresponding to the text representation of <c><anno>Pid</anno></c>.</p> <warning> - <p>This BIF is intended for debugging and for use in - the Erlang operating system. It should not be used in - application programs.</p> + <p>This BIF is intended for debugging and is not to be used + in application programs.</p> </warning> </desc> </func> + <func> <name name="port_close" arity="1"/> - <fsummary>Close an open port</fsummary> + <fsummary>Closes an open port.</fsummary> <desc> <p>Closes an open port. Roughly the same as - <c><anno>Port</anno> ! {self(), close}</c> except for the error behaviour - (see below), being synchronous, and that the port does - <em>not</em> reply with <c>{Port, closed}</c>. Any process may + <c><anno>Port</anno> ! {self(), close}</c> except for the error behavior + (see the following), being synchronous, and that the port does + <em>not</em> reply with <c>{Port, closed}</c>. Any process can close a port with <c>port_close/1</c>, not only the port owner (the connected process). If the calling process is linked to - port identified by <c><anno>Port</anno></c>, an exit signal due - to that link will be received by the process prior to the return - from <c>port_close/1</c>.</p> - <p>For comparison: <c><anno>Port</anno> ! {self(), close}</c> fails with - <c>badarg</c> if <c><anno>Port</anno></c> cannot be sent to (i.e., - <c><anno>Port</anno></c> refers neither to a port nor to a process). If - <c><anno>Port</anno></c> is a closed port nothing happens. If <c><anno>Port</anno></c> + the port identified by <c><anno>Port</anno></c>, the exit + signal from the port is guaranteed to be delivered before + <c>port_close/1</c> returns.</p> + <p>For comparison: <c><anno>Port</anno> ! {self(), close}</c> + only fails with <c>badarg</c> if <c><anno>Port</anno></c> does + not refer to a port or a process. If <c><anno>Port</anno></c> + is a closed port, nothing happens. If <c><anno>Port</anno></c> is an open port and the calling process is the port owner, - the port replies with <c>{Port, closed}</c> when all buffers - have been flushed and the port really closes, but if - the calling process is not the port owner the <em>port owner</em> fails with <c>badsig</c>.</p> - - <p>Note that any process can close a port using - <c><anno>Port</anno> ! {PortOwner, close}</c> just as if it itself was + the port replies with <c>{Port, closed}</c> when all buffers + have been flushed and the port really closes. If the calling + process is not the port owner, the <em>port owner</em> fails + with <c>badsig</c>.</p> + <p>Notice that any process can close a port using + <c><anno>Port</anno> ! {PortOwner, close}</c> as if it itself was the port owner, but the reply always goes to the port owner.</p> - <p>As of OTP-R16 <c><anno>Port</anno> ! {PortOwner, close}</c> is truly - asynchronous. Note that this operation has always been + <p>As from OTP R16, <c><anno>Port</anno> ! {PortOwner, close}</c> is truly + asynchronous. Notice that this operation has always been documented as an asynchronous operation, while the underlying implementation has been synchronous. <c>port_close/1</c> is - however still fully synchronous. This due to its error + however still fully synchronous. This because of its error behavior.</p> - <p>Failure:</p> - <taglist> - <tag><c>badarg</c></tag> - <item> - If <c><anno>Port</anno></c> is not an identifier of an open - port, or the registered name of an open port. If the calling - process was linked to the previously open port identified by - <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to this exception. - </item> - </taglist> + <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an identifier + of an open port, or the registered name of an open port. + If the calling process was previously linked to the closed + port, identified by <c><anno>Port</anno></c>, the exit + signal from the port is guaranteed to be delivered before + this <c>badarg</c> exception occurs.</p> </desc> </func> + <func> <name name="port_command" arity="2"/> - <fsummary>Send data to a port</fsummary> + <fsummary>Sends data to a port.</fsummary> <desc> <p>Sends data to a port. Same as - <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> except for the error - behaviour and being synchronous (see below). Any process may - send data to a port with <c>port_command/2</c>, not only the + <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> except + for the error + behavior and being synchronous (see the following). Any process + can send data to a port with <c>port_command/2</c>, not only the port owner (the connected process).</p> <p>For comparison: <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> - fails with <c>badarg</c> if <c><anno>Port</anno></c> cannot be sent to - (i.e., <c><anno>Port</anno></c> refers neither to a port nor to a process). - If <c><anno>Port</anno></c> is a closed port the data message disappears + only fails with <c>badarg</c> if <c><anno>Port</anno></c> + does not refer to a port or a process. If + <c><anno>Port</anno></c> is a closed port, the data message + disappears without a sound. If <c><anno>Port</anno></c> is open and the calling process is not the port owner, the <em>port owner</em> fails with <c>badsig</c>. The port owner fails with <c>badsig</c> - also if <c><anno>Data</anno></c> is not a valid IO list.</p> - <p>Note that any process can send to a port using - <c><anno>Port</anno> ! {PortOwner, {command, <anno>Data</anno>}}</c> just as if it - itself was the port owner.</p> - <p>If the port is busy, the calling process will be suspended - until the port is not busy anymore.</p> - <p>As of OTP-R16 <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> is - truly asynchronous. Note that this operation has always been + also if <c><anno>Data</anno></c> is an invalid I/O list.</p> + <p>Notice that any process can send to a port using + <c><anno>Port</anno> ! {PortOwner, {command, <anno>Data</anno>}}</c> + as if it itself was the port owner.</p> + <p>If the port is busy, the calling process is suspended + until the port is not busy any more.</p> + <p>As from OTP-R16, <c><anno>Port</anno> ! {PortOwner, {command, Data}}</c> + is truly asynchronous. Notice that this operation has always been documented as an asynchronous operation, while the underlying implementation has been synchronous. <c>port_command/2</c> is - however still fully synchronous. This due to its error + however still fully synchronous. This because of its error behavior.</p> <p>Failures:</p> <taglist> <tag><c>badarg</c></tag> <item> If <c><anno>Port</anno></c> is not an identifier of an open - port, or the registered name of an open port. If the calling - process was linked to the previously open port identified by - <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to this exception. + port, or the registered name of an open port. If the + calling process was previously linked to the closed port, + identified by <c><anno>Port</anno></c>, the exit signal + from the port is guaranteed to be delivered before this + <c>badarg</c> exception occurs. </item> <tag><c>badarg</c></tag> <item> - If <c><anno>Data</anno></c> is not a valid io list. + If <c><anno>Data</anno></c> is an invalid I/O list. </item> </taglist> </desc> </func> + <func> <name name="port_command" arity="3"/> - <fsummary>Send data to a port</fsummary> + <fsummary>Sends data to a port.</fsummary> <desc> <p>Sends data to a port. <c>port_command(Port, Data, [])</c> equals <c>port_command(Port, Data)</c>.</p> - <p>If the port command is aborted <c>false</c> is returned; - otherwise, <c>true</c> is returned.</p> - <p>If the port is busy, the calling process will be suspended - until the port is not busy anymore.</p> - <p>Currently the following <c><anno>Option</anno></c>s are valid:</p> + <p>If the port command is aborted, <c>false</c> is returned, + otherwise <c>true</c>.</p> + <p>If the port is busy, the calling process is suspended + until the port is not busy any more.</p> + <p>The following <c><anno>Option</anno></c>s are valid:</p> <taglist> <tag><c>force</c></tag> - <item>The calling process will not be suspended if the port is - busy; instead, the port command is forced through. The - call will fail with a <c>notsup</c> exception if the + <item>The calling process is not suspended if the port is + busy, instead the port command is forced through. The + call fails with a <c>notsup</c> exception if the driver of the port does not support this. For more - information see the - <seealso marker="driver_entry#driver_flags"><![CDATA[ERL_DRV_FLAG_SOFT_BUSY]]></seealso> - driver flag. + information, see driver flag + <seealso marker="driver_entry#driver_flags"><![CDATA[ERL_DRV_FLAG_SOFT_BUSY]]></seealso>. </item> <tag><c>nosuspend</c></tag> - <item>The calling process will not be suspended if the port is - busy; instead, the port command is aborted and + <item>The calling process is not suspended if the port is + busy, instead the port command is aborted and <c>false</c> is returned. </item> </taglist> <note> - <p>More options may be added in the future.</p> + <p>More options can be added in a future release.</p> </note> <p>Failures:</p> <taglist> <tag><c>badarg</c></tag> <item> If <c><anno>Port</anno></c> is not an identifier of an open - port, or the registered name of an open port. If the calling - process was linked to the previously open port identified by - <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to this exception. + port, or the registered name of an open port. If the + calling process was previously linked to the closed port, + identified by <c><anno>Port</anno></c>, the exit signal + from the port is guaranteed to be delivered before this + <c>badarg</c> exception occurs. </item> <tag><c>badarg</c></tag> <item> - If <c><anno>Data</anno></c> is not a valid io list. + If <c><anno>Data</anno></c> is an invalid I/O list. </item> <tag><c>badarg</c></tag> <item> - If <c><anno>OptionList</anno></c> is not a valid option list. + If <c><anno>OptionList</anno></c> is an invalid option list. </item> <tag><c>notsup</c></tag> <item> - If the <c>force</c> option has been passed, but the + If option <c>force</c> has been passed, but the driver of the port does not allow forcing through a busy port. </item> </taglist> </desc> </func> + <func> <name name="port_connect" arity="2"/> - <fsummary>Set the owner of a port</fsummary> + <fsummary>Sets the owner of a port.</fsummary> <desc> <p>Sets the port owner (the connected port) to <c><anno>Pid</anno></c>. - Roughly the same as <c><anno>Port</anno> ! {Owner, {connect, <anno>Pid</anno>}}</c> + Roughly the same as + <c><anno>Port</anno> ! {Owner, {connect, <anno>Pid</anno>}}</c> except for the following:</p> <list type="bulleted"> <item> - <p>The error behavior differs, see below.</p> + <p>The error behavior differs, see the following.</p> </item> <item> <p>The port does <em>not</em> reply with <c>{Port,connected}</c>.</p> </item> <item> - <p><c>port_connect/1</c> is synchronous, see below.</p> + <p><c>port_connect/1</c> is synchronous, see the following.</p> </item> <item> <p>The new port owner gets linked to the port.</p> </item> </list> - <p>The old port owner stays linked to the port and have to call - <c>unlink(Port)</c> if this is not desired. Any process may + <p>The old port owner stays linked to the port and must call + <c>unlink(Port)</c> if this is not desired. Any process can set the port owner to be any process with <c>port_connect/2</c>.</p> - <p>For comparison: <c><anno>Port</anno> ! {self(), {connect, <anno>Pid</anno>}}</c> fails - with <c>badarg</c> if <c><anno>Port</anno></c> cannot be sent to (i.e., - <c><anno>Port</anno></c> refers neither to a port nor to a process). If - <c><anno>Port</anno></c> is a closed port nothing happens. If <c><anno>Port</anno></c> + <p>For comparison: + <c><anno>Port</anno> ! {self(), {connect, <anno>Pid</anno>}}</c> + only fails with <c>badarg</c> if <c><anno>Port</anno></c> + does not refer to a port or a process. If + <c><anno>Port</anno></c> is a closed port, nothing happens. + If <c><anno>Port</anno></c> is an open port and the calling process is the port owner, the port replies with <c>{Port, connected}</c> to the old - port owner. Note that the old port owner is still linked to - the port, and that the new is not. If <c><anno>Port</anno></c> is an open + port owner. Notice that the old port owner is still linked to + the port, while the new is not. If <c><anno>Port</anno></c> is an open port and the calling process is not the port owner, the <em>port owner</em> fails with <c>badsig</c>. The port owner fails with <c>badsig</c> also if <c><anno>Pid</anno></c> is not an - existing local pid.</p> - <p>Note that any process can set the port owner using - <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c> just as if it - itself was the port owner, but the reply always goes to + existing local process identifier.</p> + <p>Notice that any process can set the port owner using + <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c> + as if it itself was the port owner, but the reply always goes to the port owner.</p> - <p>As of OTP-R16 <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c> is - truly asynchronous. Note that this operation has always been + <p>As from OTP-R16, + <c><anno>Port</anno> ! {PortOwner, {connect, <anno>Pid</anno>}}</c> is + truly asynchronous. Notice that this operation has always been documented as an asynchronous operation, while the underlying implementation has been synchronous. <c>port_connect/2</c> is - however still fully synchronous. This due to its error + however still fully synchronous. This because of its error behavior.</p> <p>Failures:</p> <taglist> <tag><c>badarg</c></tag> <item> - If <c><anno>Port</anno></c> is not an identifier of an open - port, or the registered name of an open port. If the calling - process was linked to the previously open port identified by - <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to this exception. + If <c><anno>Port</anno></c> is not an identifier of an open port, or + the registered name of an open port. If the calling + process was previously linked to the closed port, + identified by <c><anno>Port</anno></c>, the exit signal + from the port is guaranteed to be delivered before this + <c>badarg</c> exception occurs. </item> <tag><c>badarg</c></tag> <item>If process identified by <c>Pid</c> is not an existing @@ -3233,53 +3851,75 @@ os_prompt% </pre> </taglist> </desc> </func> + <func> <name name="port_control" arity="3"/> - <fsummary>Perform a synchronous control operation on a port</fsummary> + <fsummary>Performs a synchronous control operation on a port.</fsummary> <desc> <p>Performs a synchronous control operation on a port. - The meaning of <c><anno>Operation</anno></c> and <c><anno>Data</anno></c> depends on - the port, i.e., on the port driver. Not all port drivers + The meaning of <c><anno>Operation</anno></c> and + <c><anno>Data</anno></c> depends on + the port, that is, on the port driver. Not all port drivers support this control feature.</p> - <p>Returns: a list of integers in the range 0 through 255, or a + <p>Returns a list of integers in the range 0..255, or a binary, depending on the port driver. The meaning of the returned data also depends on the port driver.</p> - <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not an open port or - the registered name of an open port, if <c><anno>Operation</anno></c> - cannot fit in a 32-bit integer, if the port driver does not - support synchronous control operations, or if the port driver - so decides for any reason (probably something wrong with - <c><anno>Operation</anno></c> or <c><anno>Data</anno></c>).</p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item> + If <c><anno>Port</anno></c> is not an open port or the registered + name of an open port. + </item> + <tag><c>badarg</c></tag> + <item> + If <c><anno>Operation</anno></c> cannot fit in a 32-bit integer. + </item> + <tag><c>badarg</c></tag> + <item> + If the port driver does not support synchronous control + operations. + </item> + <tag><c>badarg</c></tag> + <item> + If the port driver so decides for any reason (probably + something wrong with <c><anno>Operation</anno></c> or + <c><anno>Data</anno></c>). + </item> + </taglist> </desc> </func> + <func> <name name="port_call" arity="3"/> - <fsummary>Synchronous call to a port with term data</fsummary> + <fsummary>Performs a synchronous call to a port with term data.</fsummary> <desc> <p>Performs a synchronous call to a port. The meaning of - <c><anno>Operation</anno></c> and <c><anno>Data</anno></c> depends on the port, i.e., + <c><anno>Operation</anno></c> and <c><anno>Data</anno></c> + depends on the port, that is, on the port driver. Not all port drivers support this feature.</p> - <p><c><anno>Port</anno></c> is a port identifier, referring to a driver.</p> + <p><c><anno>Port</anno></c> is a port identifier, + referring to a driver.</p> <p><c><anno>Operation</anno></c> is an integer, which is passed on to the driver.</p> - <p><c><anno>Data</anno></c> is any Erlang term. This data is converted to - binary term format and sent to the port.</p> - <p>Returns: a term from the driver. The meaning of the returned + <p><c><anno>Data</anno></c> is any Erlang term. This data is converted + to binary term format and sent to the port.</p> + <p>Returns a term from the driver. The meaning of the returned data also depends on the port driver.</p> <p>Failures:</p> <taglist> <tag><c>badarg</c></tag> <item> - If <c><anno>Port</anno></c> is not an identifier of an open - port, or the registered name of an open port. If the calling - process was linked to the previously open port identified by - <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to this exception. + If <c><anno>Port</anno></c> is not an identifier of an open port, + or the registered name of an open port. If the calling + process was previously linked to the closed port, + identified by <c><anno>Port</anno></c>, the exit signal + from the port is guaranteed to be delivered before this + <c>badarg</c> exception occurs. </item> <tag><c>badarg</c></tag> <item> - If <c><anno>Operation</anno></c> does not fit in a - 32-bit integer. + If <c><anno>Operation</anno></c> does not fit in a 32-bit integer. </item> <tag><c>badarg</c></tag> <item> @@ -3289,171 +3929,183 @@ os_prompt% </pre> <tag><c>badarg</c></tag> <item> If the port driver so decides for any reason (probably - something wrong with <c><anno>Operation</anno></c>, or - <c><anno>Data</anno></c>). + something wrong with <c><anno>Operation</anno></c> + or <c><anno>Data</anno></c>). </item> </taglist> </desc> </func> + <func> <name name="port_info" arity="1"/> - <fsummary>Information about a port</fsummary> + <fsummary>Information about a port.</fsummary> <desc> <p>Returns a list containing tuples with information about - the <c><anno>Port</anno></c>, or <c>undefined</c> if the port is not open. - The order of the tuples is not defined, nor are all the - tuples mandatory. - If <c>undefined</c> is returned and the calling process - was linked to a previously open port identified by - <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/1</c>.</p> - <p>Currently the result will containt information about the - following <c>Item</c>s: <c>registered_name</c> (if the port has - a registered name), <c>id</c>, <c>connected</c>, <c>links</c>, - <c>name</c>, <c>input</c>, and <c>output</c>. For more information - about the different <c>Item</c>s, see + <c><anno>Port</anno></c>, or <c>undefined</c> if the port is not open. + The order of the tuples is undefined, and all the + tuples are not mandatory. + If the port is closed and the calling process + was previously linked to the port, the exit signal from the + port is guaranteed to be delivered before <c>port_info/1</c> + returns <c>undefined</c>.</p> + <p>The result contains information about the following + <c>Item</c>s:</p> + <list type="bulleted"> + <item><c>registered_name</c> (if the port has a registered + name)</item> + <item><c>id</c></item> + <item><c>connected</c></item> + <item><c>links</c></item> + <item><c>name</c></item> + <item><c>input</c></item> + <item><c>output</c></item> + </list> + <p>For more information about the different <c>Item</c>s, see <seealso marker="#port_info/2">port_info/2</seealso>.</p> <p>Failure: <c>badarg</c> if <c>Port</c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="1"/> - <fsummary>Information about the connected process of a port</fsummary> + <fsummary>Information about the connected process of a port.</fsummary> <desc> <p><c><anno>Pid</anno></c> is the process identifier of the process connected to the port.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="2"/> - <fsummary>Information about the internal index of a port</fsummary> + <fsummary>Information about the internal index of a port.</fsummary> <desc> <p><c><anno>Index</anno></c> is the internal index of the port. This - index may be used to separate ports.</p> + index can be used to separate ports.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="3"/> - <fsummary>Information about the input of a port</fsummary> + <fsummary>Information about the input of a port.</fsummary> <desc> <p><c><anno>Bytes</anno></c> is the total number of bytes read from the port.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="4"/> - <fsummary>Information about the links of a port</fsummary> + <fsummary>Information about the links of a port.</fsummary> <desc> <p><c><anno>Pids</anno></c> is a list of the process identifiers of the processes that the port is linked to.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="5"/> - <fsummary>Information about the locking of a port</fsummary> + <fsummary>Information about the locking of a port.</fsummary> <desc> - <p><c><anno>Locking</anno></c> is currently either <c>false</c> - (emulator without SMP support), <c>port_level</c> (port specific - locking), or <c>driver_level</c> (driver specific locking). Note - that these results are highly implementation specific and might - change in the future.</p> + <p><c><anno>Locking</anno></c> is one of the following:</p> + <list type="bulleted"> + <item><c>false</c> (emulator without SMP support)</item> + <item><c>port_level</c> (port-specific locking)</item> + <item><c>driver_level</c> (driver-specific locking)</item> + </list> + <p>Notice that these results are highly implementation-specific + and can change in a future release.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="6"/> - <fsummary>Information about the memory size of a port</fsummary> + <fsummary>Information about the memory size of a port.</fsummary> <desc> - <p><c><anno>Bytes</anno></c> is the total amount of memory, - in bytes, allocated for this port by the runtime system. Note - that the port itself might have allocated memory which is not + <p><c><anno>Bytes</anno></c> is the total number of + bytes allocated for this port by the runtime system. The + port itself can have allocated memory that is not included in <c><anno>Bytes</anno></c>.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="7"/> - <fsummary>Information about the monitors of a port</fsummary> + <fsummary>Information about the monitors of a port.</fsummary> <desc> <p><c><anno>Monitors</anno></c> represent processes that this port - is monitoring.</p> + monitors.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="8"/> - <fsummary>Information about the name of a port</fsummary> + <fsummary>Information about the name of a port.</fsummary> <desc> <p><c><anno>Name</anno></c> is the command name set by <seealso marker="#open_port/2">open_port/2</seealso>.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="9"/> - <fsummary>Information about the OS pid of a port</fsummary> + <fsummary>Information about the OS pid of a port.</fsummary> <desc> <p><c><anno>OsPid</anno></c> is the process identifier (or equivalent) of an OS process created with @@ -3461,432 +4113,464 @@ os_prompt% </pre> Command}, Options)</seealso>. If the port is not the result of spawning an OS process, the value is <c>undefined</c>.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="10"/> - <fsummary>Information about the output of a port</fsummary> + <fsummary>Information about the output of a port.</fsummary> <desc> <p><c><anno>Bytes</anno></c> is the total number of bytes written - to the port from Erlang processes using either + to the port from Erlang processes using <seealso marker="#port_command/2">port_command/2</seealso>, <seealso marker="#port_command/3">port_command/3</seealso>, - or <c><anno>Port</anno> ! {Owner, {command, Data}</c>. - </p> + or <c><anno>Port</anno> ! {Owner, {command, Data}</c>.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="11"/> - <fsummary>Information about the parallelism hint of a port</fsummary> + <fsummary>Information about the parallelism hint of a port.</fsummary> <desc> <p><c><anno>Boolean</anno></c> corresponds to the port parallelism - hint being used by this port. For more information see - the <seealso marker="#open_port_parallelism">parallelism</seealso> - option of <seealso marker="#open_port/2">open_port/2</seealso>.</p> + hint being used by this port. For more information, see option + <seealso marker="#open_port_parallelism">parallelism</seealso> + of <seealso marker="#open_port/2">open_port/2</seealso>.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="12"/> - <fsummary>Information about the queue size of a port</fsummary> + <fsummary>Information about the queue size of a port.</fsummary> <desc> - <p><c><anno>Bytes</anno></c> is the total amount of data, - in bytes, queued by the port using the ERTS driver queue + <p><c><anno>Bytes</anno></c> is the total number + of bytes queued by the port using the <c>ERTS</c> driver queue implementation.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_info" arity="2" clause_i="13"/> - <fsummary>Information about the registered name of a port</fsummary> + <fsummary>Information about the registered name of a port.</fsummary> <desc> <p><c><anno>RegisteredName</anno></c> is the registered name of the port. If the port has no registered name, <c>[]</c> is returned.</p> <p>If the port identified by <c><anno>Port</anno></c> is not open, - <c>undefined</c> is returned. If <c>undefined</c> is returned and - the calling process was linked to a previously open port identified - by <c><anno>Port</anno></c>, an exit signal due to this link - was received by the process prior to the return from - <c>port_info/2</c>.</p> + <c>undefined</c> is returned. If the port is closed and the + calling process was previously linked to the port, the exit + signal from the port is guaranteed to be delivered before + <c>port_info/2</c> returns <c>undefined</c>.</p> <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port identifier, or an atom.</p> </desc> </func> + <func> <name name="port_to_list" arity="1"/> - <fsummary>Text representation of a port identifier</fsummary> + <fsummary>Text representation of a port identifier.</fsummary> <desc> - <p>Returns a string which corresponds to the text + <p>Returns a string corresponding to the text representation of the port identifier <c><anno>Port</anno></c>.</p> <warning> - <p>This BIF is intended for debugging and for use in - the Erlang operating system. It should not be used in - application programs.</p> + <p>This BIF is intended for debugging. It is not to be used + in application programs.</p> </warning> </desc> </func> + <func> <name name="ports" arity="0"/> - <fsummary>All open ports</fsummary> + <fsummary>Lists all existing ports.</fsummary> <desc> <p>Returns a list of port identifiers corresponding to all the - ports currently existing on the local node.</p> - - <p>Note that a port that is exiting, exists but is not open.</p> + ports existing on the local node.</p> + <p>Notice that an exiting port exists, but is not open.</p> </desc> </func> + <func> <name name="pre_loaded" arity="0"/> - <fsummary>List of all pre-loaded modules</fsummary> + <fsummary>Lists all pre-loaded modules.</fsummary> <desc> - <p>Returns a list of Erlang modules which are pre-loaded in + <p>Returns a list of Erlang modules that are preloaded in the system. As all loading of code is done through the file system, the file system must have been loaded previously. - Hence, at least the module <c>init</c> must be pre-loaded.</p> + Hence, at least the module <c>init</c> must be preloaded.</p> </desc> </func> + <func> <name name="process_display" arity="2"/> - <fsummary>Write information about a local process on standard error</fsummary> + <fsummary>Writes information about a local process on standard error.</fsummary> <desc> <p>Writes information about the local process <c><anno>Pid</anno></c> on - standard error. The currently allowed value for the atom + standard error. The only allowed value for the atom <c><anno>Type</anno></c> is <c>backtrace</c>, which shows the contents of the call stack, including information about the call chain, with the current function printed first. The format of the output is not further defined.</p> </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="1"/> - <fsummary>Set process flag trap_exit for the calling process</fsummary> + <fsummary>Sets process flag <c>trap_exit</c> for the calling process.</fsummary> <desc> <p>When <c>trap_exit</c> is set to <c>true</c>, exit signals - arriving to a process are converted to <c>{'EXIT', From, Reason}</c> messages, which can be received as ordinary + arriving to a process are converted to <c>{'EXIT', From, Reason}</c> + messages, which can be received as ordinary messages. If <c>trap_exit</c> is set to <c>false</c>, the process exits if it receives an exit signal other than <c>normal</c> and the exit signal is propagated to its - linked processes. Application processes should normally - not trap exits.</p> + linked processes. Application processes are normally + not to trap exits.</p> <p>Returns the old value of the flag.</p> <p>See also <seealso marker="#exit/2">exit/2</seealso>.</p> </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="2"/> - <fsummary>Set process flag error_handler for the calling process</fsummary> + <fsummary>Sets process flag <c>error_handler</c> for the calling process.</fsummary> <desc> - <p>This is used by a process to redefine the error handler + <p>Used by a process to redefine the error handler for undefined function calls and undefined registered - processes. Inexperienced users should not use this flag - since code auto-loading is dependent on the correct + processes. Inexperienced users are not to use this flag, + as code auto-loading depends on the correct operation of the error handling module.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="3"/> - <fsummary>Set process flag min_heap_size for the calling process</fsummary> + <fsummary>Sets process flag <c>min_heap_size</c> for the calling process.</fsummary> <desc> - <p>This changes the minimum heap size for the calling - process.</p> + <p>Changes the minimum heap size for the calling process.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="4"/> - <fsummary>Set process flag min_bin_vheap_size for the calling process</fsummary> + <fsummary>Sets process flag <c>min_bin_vheap_size</c> for the calling process.</fsummary> <desc> - <p>This changes the minimum binary virtual heap size for the calling + <p>Changes the minimum binary virtual heap size for the calling process.</p> - <p>Returns the old value of the flag.</p> </desc> + <p>Returns the old value of the flag.</p> + </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="5"/> + <fsummary>Sets process flag <c>priority</c> for the calling process.</fsummary> <type name="priority_level"/> - <fsummary>Set process flag priority for the calling process</fsummary> <desc> <p><marker id="process_flag_priority"></marker> - This sets the process priority. <c><anno>Level</anno></c> is an atom. - There are currently four priority levels: <c>low</c>, - <c>normal</c>, <c>high</c>, and <c>max</c>. The default - priority level is <c>normal</c>. <em>NOTE</em>: The - <c>max</c> priority level is reserved for internal use in - the Erlang runtime system, and should <em>not</em> be used - by others. - </p> - <p>Internally in each priority level processes are scheduled - in a round robin fashion. - </p> + Sets the process priority. <c><anno>Level</anno></c> is an atom. + There are four priority levels: <c>low</c>, + <c>normal</c>, <c>high</c>, and <c>max</c>. Default + is <c>normal</c>.</p> + <note> + <p>Priority level <c>max</c> is reserved for internal use in + the Erlang runtime system, and is <em>not</em> to be used + by others.</p> + </note> + <p>Internally in each priority level, processes are scheduled + in a round robin fashion.</p> <p>Execution of processes on priority <c>normal</c> and - priority <c>low</c> will be interleaved. Processes on - priority <c>low</c> will be selected for execution less - frequently than processes on priority <c>normal</c>. - </p> - <p>When there are runnable processes on priority <c>high</c> - no processes on priority <c>low</c>, or <c>normal</c> will - be selected for execution. Note, however, that this does - <em>not</em> mean that no processes on priority <c>low</c>, - or <c>normal</c> will be able to run when there are - processes on priority <c>high</c> running. On the runtime - system with SMP support there might be more processes running - in parallel than processes on priority <c>high</c>, i.e., - a <c>low</c>, and a <c>high</c> priority process might - execute at the same time. - </p> - <p>When there are runnable processes on priority <c>max</c> + <c>low</c> are interleaved. Processes on priority + <c>low</c> are selected for execution less + frequently than processes on priority <c>normal</c>.</p> + <p>When there are runnable processes on priority <c>high</c>, + no processes on priority <c>low</c> or <c>normal</c> are + selected for execution. Notice however, that this does + <em>not</em> mean that no processes on priority <c>low</c> + or <c>normal</c> can run when there are processes + running on priority <c>high</c>. On the runtime + system with SMP support, more processes can be running + in parallel than processes on priority <c>high</c>, that is, + a <c>low</c> and a <c>high</c> priority process can + execute at the same time.</p> + <p>When there are runnable processes on priority <c>max</c>, no processes on priority <c>low</c>, <c>normal</c>, or - <c>high</c> will be selected for execution. As with the - <c>high</c> priority, processes on lower priorities might - execute in parallel with processes on priority <c>max</c>. - </p> + <c>high</c> are selected for execution. As with priority + <c>high</c>, processes on lower priorities can + execute in parallel with processes on priority <c>max</c>.</p> <p>Scheduling is preemptive. Regardless of priority, a process - is preempted when it has consumed more than a certain amount + is preempted when it has consumed more than a certain number of reductions since the last time it was selected for - execution. - </p> - <p><em>NOTE</em>: You should not depend on the scheduling + execution.</p> + <note> + <p>Do not depend on the scheduling to remain exactly as it is today. Scheduling, at least on - the runtime system with SMP support, is very likely to be - modified in the future in order to better utilize available - processor cores. - </p> - <p>There is currently <em>no</em> automatic mechanism for - avoiding priority inversion, such as priority inheritance, - or priority ceilings. When using priorities you have - to take this into account and handle such scenarios by - yourself. - </p> + the runtime system with SMP support, is likely to be + changed in a future release to use available + processor cores better.</p> + </note> + <p>There is <em>no</em> automatic mechanism for + avoiding priority inversion, such as priority inheritance + or priority ceilings. When using priorities, + take this into account and handle such scenarios by + yourself.</p> <p>Making calls from a <c>high</c> priority process into code - that you don't have control over may cause the <c>high</c> - priority process to wait for a processes with lower - priority, i.e., effectively decreasing the priority of the + that you have no control over can cause the <c>high</c> + priority process to wait for a process with lower + priority. That is, effectively decreasing the priority of the <c>high</c> priority process during the call. Even if this - isn't the case with one version of the code that you don't - have under your control, it might be the case in a future - version of it. This might, for example, happen if a - <c>high</c> priority process triggers code loading, since - the code server runs on priority <c>normal</c>. - </p> + is not the case with one version of the code that you have no + control over, it can be the case in a future + version of it. This can, for example, occur if a + <c>high</c> priority process triggers code loading, as + the code server runs on priority <c>normal</c>.</p> <p>Other priorities than <c>normal</c> are normally not needed. - When other priorities are used, they need to be used - with care, especially the <c>high</c> priority <em>must</em> - be used with care. A process on <c>high</c> priority should - only perform work for short periods of time. Busy looping for - long periods of time in a <c>high</c> priority process will - most likely cause problems, since there are important servers - in OTP running on priority <c>normal</c>. - </p> + When other priorities are used, use them with care, + <em>especially</em> priority <c>high</c>. A + process on priority <c>high</c> is only + to perform work for short periods. Busy looping for + long periods in a <c>high</c> priority process does + most likely cause problems, as important OTP servers + run on priority <c>normal</c>.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="6"/> - <fsummary>Set process flag save_calls for the calling process</fsummary> + <fsummary>Sets process flag <c>save_calls</c> for the calling process.</fsummary> <desc> <p><c><anno>N</anno></c> must be an integer in the interval 0..10000. - If <c><anno>N</anno></c> > 0, call saving is made active for the - process, which means that information about the <c><anno>N</anno></c> - most recent global function calls, BIF calls, sends and + If <c><anno>N</anno></c> is greater than 0, call saving is made + active for the + process. This means that information about the <c><anno>N</anno></c> + most recent global function calls, BIF calls, sends, and receives made by the process are saved in a list, which can be retrieved with <c>process_info(Pid, last_calls)</c>. A global function call is one in which the module of the function is explicitly mentioned. Only a fixed amount of information - is saved: a tuple <c>{Module, Function, Arity}</c> for - function calls, and the mere atoms <c>send</c>, - <c>'receive'</c> and <c>timeout</c> for sends and receives - (<c>'receive'</c> when a message is received and - <c>timeout</c> when a receive times out). If <c>N</c> = 0, + is saved, as follows:</p> + <list type="bulleted"> + <item>A tuple <c>{Module, Function, Arity}</c> for + function calls</item> + <item> The atoms <c>send</c>, <c>'receive'</c>, and + <c>timeout</c> for sends and receives (<c>'receive'</c> + when a message is received and <c>timeout</c> when a + receive times out)</item> + </list> + <p>If <c>N</c> = 0, call saving is disabled for the process, which is the default. Whenever the size of the call saving list is set, its contents are reset.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> <name name="process_flag" arity="2" clause_i="7"/> - <fsummary>Set process flag sensitive for the calling process</fsummary> + <fsummary>Sets process flag <c>sensitive</c> for the calling process.</fsummary> <desc> - <p>Set or clear the <c>sensitive</c> flag for the current process. + <p>Sets or clears flag <c>sensitive</c> for the current process. When a process has been marked as sensitive by calling - <c>process_flag(sensitive, true)</c>, features in the run-time - system that can be used for examining the data and/or inner working + <c>process_flag(sensitive, true)</c>, features in the runtime + system that can be used for examining the data or inner working of the process are silently disabled.</p> <p>Features that are disabled include (but are not limited to) the following:</p> - <p>Tracing: Trace flags can still be set for the process, but no - trace messages of any kind will be generated. - (If the <c>sensitive</c> flag is turned off, trace messages will - again be generated if there are any trace flags set.)</p> - <p>Sequential tracing: The sequential trace token will be propagated - as usual, but no sequential trace messages will be generated.</p> - <p><c>process_info/1,2</c> cannot be used to read out the message - queue or the process dictionary (both will be returned as empty lists).</p> + <list type="bulleted"> + <item>Tracing: Trace flags can still be set for the process, + but no trace messages of any kind are generated. (If flag + <c>sensitive</c> is turned off, trace messages are again + generated if any trace flags are set.)</item> + <item>Sequential tracing: The sequential trace token is + propagated as usual, but no sequential trace messages are + generated.</item> + </list> + <p><c>process_info/1,2</c> cannot be used to read out the + message queue or the process dictionary (both are returned + as empty lists).</p> <p>Stack back-traces cannot be displayed for the process.</p> <p>In crash dumps, the stack, messages, and the process dictionary - will be omitted.</p> + are omitted.</p> <p>If <c>{save_calls,N}</c> has been set for the process, no - function calls will be saved to the call saving list. - (The call saving list will not be cleared; furthermore, send, receive, - and timeout events will still be added to the list.)</p> + function calls are saved to the call saving list. + (The call saving list is not cleared. Furthermore, send, receive, + and timeout events are still added to the list.)</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> <name name="process_flag" arity="3"/> - <fsummary>Set process flags for a process</fsummary> + <fsummary>Sets process flags for a process.</fsummary> <desc> - <p>Sets certain flags for the process <c><anno>Pid</anno></c>, in the same - manner as + <p>Sets certain flags for the process <c><anno>Pid</anno></c>, + in the same manner as <seealso marker="#process_flag/2">process_flag/2</seealso>. - Returns the old value of the flag. The allowed values for + Returns the old value of the flag. The valid values for <c><anno>Flag</anno></c> are only a subset of those allowed in - <c>process_flag/2</c>, namely: <c>save_calls</c>.</p> - <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c> is not a local process.</p> + <c>process_flag/2</c>, namely <c>save_calls</c>.</p> + <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c> + is not a local process.</p> </desc> </func> + <func> <name name="process_info" arity="1"/> + <fsummary>Information about a process.</fsummary> <type name="process_info_result_item"/> <type name="priority_level"/> <type name="stack_item"/> - <fsummary>Information about a process</fsummary> <desc> <p>Returns a list containing <c><anno>InfoTuple</anno></c>s with miscellaneous information about the process identified by - <c>Pid</c>, or <c>undefined</c> if the process is not alive. - </p> - <p> - The order of the <c><anno>InfoTuple</anno></c>s is not defined, nor - are all the <c><anno>InfoTuple</anno></c>s mandatory. The <c><anno>InfoTuple</anno></c>s - part of the result may be changed without prior notice. - Currently <c><anno>InfoTuple</anno></c>s with the following items - are part of the result: - <c>current_function</c>, <c>initial_call</c>, <c>status</c>, - <c>message_queue_len</c>, <c>messages</c>, <c>links</c>, - <c>dictionary</c>, <c>trap_exit</c>, <c>error_handler</c>, - <c>priority</c>, <c>group_leader</c>, <c>total_heap_size</c>, - <c>heap_size</c>, <c>stack_size</c>, <c>reductions</c>, and - <c>garbage_collection</c>. - If the process identified by <c><anno>Pid</anno></c> has a registered name - also an <c><anno>InfoTuple</anno></c> with the item <c>registered_name</c> - will appear. - </p> - <p>See <seealso marker="#process_info/2">process_info/2</seealso> - for information about specific <c><anno>InfoTuple</anno></c>s.</p> + <c>Pid</c>, or <c>undefined</c> if the process is not alive.</p> + <p>The order of the <c><anno>InfoTuple</anno></c>s is undefined and + all <c><anno>InfoTuple</anno></c>s are not mandatory. + The <c><anno>InfoTuple</anno></c>s + part of the result can be changed without prior notice.</p> + <p>The <c><anno>InfoTuple</anno></c>s with the following items + are part of the result:</p> + <list type="bulleted"> + <item><c>current_function</c></item> + <item><c>initial_call</c></item> + <item><c>status</c></item> + <item><c>message_queue_len</c></item> + <item><c>messages</c></item> + <item><c>links</c></item> + <item><c>dictionary</c></item> + <item><c>trap_exit</c></item> + <item><c>error_handler</c></item> + <item><c>priority</c></item> + <item><c>group_leader</c></item> + <item><c>total_heap_size</c></item> + <item><c>heap_size</c></item> + <item><c>stack_size</c></item> + <item><c>reductions</c></item> + <item><c>garbage_collection</c></item> + </list> + <p>If the process identified by <c><anno>Pid</anno></c> has a + registered name, + also an <c><anno>InfoTuple</anno></c> with item <c>registered_name</c> + appears.</p> + <p>For information about specific <c><anno>InfoTuple</anno></c>s, see + <seealso marker="#process_info/2">process_info/2</seealso>.</p> <warning> - <p>This BIF is intended for <em>debugging only</em>, use - <seealso marker="#process_info/2">process_info/2</seealso> - for all other purposes. - </p> + <p>This BIF is intended for <em>debugging only</em>. For + all other purposes, use + <seealso marker="#process_info/2">process_info/2</seealso>.</p> </warning> - <p>Failure: <c>badarg</c> if <c>Pid</c> is not a local process.</p> + <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c> is not a + local process.</p> </desc> </func> + <func> <name name="process_info" arity="2" clause_i="1"/> <name name="process_info" arity="2" clause_i="2"/> + <fsummary>Information about a process.</fsummary> <type name="process_info_item"/> <type name="process_info_result_item"/> <type name="stack_item"/> <type name="priority_level"/> - <fsummary>Information about a process</fsummary> <desc> - <p>Returns information about the process identified by <c><anno>Pid</anno></c> - as specified by the <c><anno>Item</anno></c> or the <c><anno>ItemList</anno></c>, or <c>undefined</c> if the - process is not alive. - </p> - <p>If the process is alive and a single <c><anno>Item</anno></c> is given, - the returned value is the corresponding - <c><anno>InfoTuple</anno></c> unless <c>Item =:= registered_name</c> - and the process has no registered name. In this case - <c>[]</c> is returned. This strange behavior is due to - historical reasons, and is kept for backward compatibility. - </p> - <p>If an <c>ItemList</c> is given, the result is an - <c><anno>InfoTupleList</anno></c>. The <c><anno>InfoTuple</anno></c>s in the - <c><anno>InfoTupleList</anno></c> will appear with the corresponding - <c><anno>Item</anno></c>s in the same order as the <c><anno>Item</anno></c>s appeared - in the <c><anno>ItemList</anno></c>. Valid <c><anno>Item</anno></c>s may appear multiple - times in the <c><anno>ItemList</anno></c>. - </p> - <note><p>If <c>registered_name</c> is part of an <c><anno>ItemList</anno></c> + <p>Returns information about the process identified by + <c><anno>Pid</anno></c>, as specified by + <c><anno>Item</anno></c> or <c><anno>ItemList</anno></c>. + Returns <c>undefined</c> if the process is not alive.</p> + <p>If the process is alive and a single <c><anno>Item</anno></c> + is given, the returned value is the corresponding + <c><anno>InfoTuple</anno></c>, unless <c>Item =:= registered_name</c> + and the process has no registered name. In this case, + <c>[]</c> is returned. This strange behavior is because of + historical reasons, and is kept for backward compatibility.</p> + <p>If <c><anno>ItemList</anno></c> is given, the result is + <c><anno>InfoTupleList</anno></c>. + The <c><anno>InfoTuple</anno></c>s in + <c><anno>InfoTupleList</anno></c> appear with the corresponding + <c><anno>Item</anno></c>s in the same order as the + <c><anno>Item</anno></c>s appeared + in <c><anno>ItemList</anno></c>. Valid <c><anno>Item</anno></c>s can + appear multiple times in <c><anno>ItemList</anno></c>.</p> + <note><p>If <c>registered_name</c> is part of <c><anno>ItemList</anno></c> and the process has no name registered a - <c>{registered_name, []}</c> <c><anno>InfoTuple</anno></c> <em>will</em> - appear in the resulting <c><anno>InfoTupleList</anno></c>. This - behavior is different than when a single - <c>Item =:= registered_name</c> is given, and than when - <c>process_info/1</c> is used. - </p></note> - <p>Currently the following <c><anno>InfoTuple</anno></c>s with corresponding + <c>{registered_name, []}</c>, <c><anno>InfoTuple</anno></c> + <em>will</em> appear in the resulting + <c><anno>InfoTupleList</anno></c>. This + behavior is different when a single + <c>Item =:= registered_name</c> is given, and when + <c>process_info/1</c> is used.</p> + </note> + <p>The following <c><anno>InfoTuple</anno></c>s with corresponding <c><anno>Item</anno></c>s are valid:</p> <taglist> <tag><c>{backtrace, <anno>Bin</anno>}</c></tag> <item> - <p>The binary <c><anno>Bin</anno></c> contains the same information as - the output from + <p>Binary <c><anno>Bin</anno></c> contains the same information + as the output from <c>erlang:process_display(<anno>Pid</anno>, backtrace)</c>. Use <c>binary_to_list/1</c> to obtain the string of characters from the binary.</p> </item> <tag><c>{binary, <anno>BinInfo</anno>}</c></tag> <item> - <p><c><anno>BinInfo</anno></c> is a list containing miscellaneous information - about binaries currently being referred to by this process. - This <c><anno>InfoTuple</anno></c> may be changed or removed without prior - notice.</p> + <p><c><anno>BinInfo</anno></c> is a list containing miscellaneous + information about binaries currently being referred to by this + process. This <c><anno>InfoTuple</anno></c> can be changed or + removed without prior notice.</p> </item> <tag><c>{catchlevel, <anno>CatchLevel</anno>}</c></tag> <item> <p><c><anno>CatchLevel</anno></c> is the number of currently active - catches in this process. This <c><anno>InfoTuple</anno></c> may be + catches in this process. This <c><anno>InfoTuple</anno></c> can be changed or removed without prior notice.</p> </item> - <tag><c>{current_function, {<anno>Module</anno>, <anno>Function</anno>, <anno>Arity</anno>}}</c></tag> + <tag><c>{current_function, {<anno>Module</anno>, + <anno>Function</anno>, Arity}}</c></tag> <item> - <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>, <c><anno>Arity</anno></c> is + <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>, + <c><anno>Arity</anno></c> is the current function call of the process.</p> </item> - <tag><c>{current_location, {<anno>Module</anno>, <anno>Function</anno>, <anno>Arity</anno>, <anno>Location</anno>}}</c></tag> + <tag><c>{current_location, {<anno>Module</anno>, + <anno>Function</anno>, <anno>Arity</anno>, + <anno>Location</anno>}}</c></tag> <item> - <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>, <c><anno>Arity</anno></c> is + <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>, + <c><anno>Arity</anno></c> is the current function call of the process. - <c><anno>Location</anno></c> is a list of two-tuples that describes the - location in the source code. - </p> + <c><anno>Location</anno></c> is a list of two-tuples describing the + location in the source code.</p> </item> <tag><c>{current_stacktrace, <anno>Stack</anno>}</c></tag> <item> - <p>Return the current call stack back-trace (<em>stacktrace</em>) + <p>Returns the current call stack back-trace (<em>stacktrace</em>) of the process. The stack has the same format as returned by - <seealso marker="#get_stacktrace/0">erlang:get_stacktrace/0</seealso>. - </p> + <seealso marker="#get_stacktrace/0">erlang:get_stacktrace/0</seealso>.</p> </item> <tag><c>{dictionary, <anno>Dictionary</anno>}</c></tag> <item> - <p><c><anno>Dictionary</anno></c> is the dictionary of the process.</p> + <p><c><anno>Dictionary</anno></c> is the process dictionary.</p> </item> <tag><c>{error_handler, <anno>Module</anno>}</c></tag> <item> @@ -3895,34 +4579,36 @@ os_prompt% </pre> </item> <tag><c>{garbage_collection, <anno>GCInfo</anno>}</c></tag> <item> - <p><c><anno>GCInfo</anno></c> is a list which contains miscellaneous + <p><c><anno>GCInfo</anno></c> is a list containing miscellaneous information about garbage collection for this process. - The content of <c><anno>GCInfo</anno></c> may be changed without + The content of <c><anno>GCInfo</anno></c> can be changed without prior notice.</p> </item> <tag><c>{group_leader, <anno>GroupLeader</anno>}</c></tag> <item> - <p><c><anno>GroupLeader</anno></c> is group leader for the IO of + <p><c><anno>GroupLeader</anno></c> is group leader for the I/O of the process.</p> </item> <tag><c>{heap_size, <anno>Size</anno>}</c></tag> <item> - <p><c><anno>Size</anno></c> is the size in words of youngest heap generation - of the process. This generation currently include the stack - of the process. This information is highly implementation - dependent, and may change if the implementation change. - </p> + <p><c><anno>Size</anno></c> is the size in words of the youngest heap + generation of the process. This generation includes + the process stack. This information is highly + implementation-dependent, and can change if the + implementation changes.</p> </item> - <tag><c>{initial_call, {Module, Function, Arity}}</c></tag> + <tag><c>{initial_call, {<anno>Module</anno>, <anno>Function</anno>, + <anno>Arity</anno>}}</c></tag> <item> - <p><c>Module</c>, <c>Function</c>, <c>Arity</c> is + <p><c><anno>Module</anno></c>, <c><anno>Function</anno></c>, + <c><anno>Arity</anno></c> is the initial function call with which the process was spawned.</p> </item> <tag><c>{links, <anno>PidsAndPorts</anno>}</c></tag> <item> - <p><c><anno>PidsAndPorts</anno></c> is a list of pids and - port identifiers, with processes or ports to which the process + <p><c><anno>PidsAndPorts</anno></c> is a list of process identifiers + and port identifiers, with processes or ports to which the process has a link.</p> </item> <tag><c>{last_calls, false|Calls}</c></tag> @@ -3936,14 +4622,14 @@ os_prompt% </pre> <tag><c>{memory, <anno>Size</anno>}</c></tag> <item> <p><c><anno>Size</anno></c> is the size in bytes of the process. This - includes call stack, heap and internal structures.</p> + includes call stack, heap, and internal structures.</p> </item> <tag><c>{message_queue_len, <anno>MessageQueueLen</anno>}</c></tag> <item> <p><c><anno>MessageQueueLen</anno></c> is the number of messages currently in the message queue of the process. This is the length of the list <c><anno>MessageQueue</anno></c> returned as - the info item <c>messages</c> (see below).</p> + the information item <c>messages</c> (see the following).</p> </item> <tag><c>{messages, <anno>MessageQueue</anno>}</c></tag> <item> @@ -3952,31 +4638,35 @@ os_prompt% </pre> </item> <tag><c>{min_heap_size, <anno>MinHeapSize</anno>}</c></tag> <item> - <p><c><anno>MinHeapSize</anno></c> is the minimum heap size for the process.</p> + <p><c><anno>MinHeapSize</anno></c> is the minimum heap size + for the process.</p> </item> <tag><c>{min_bin_vheap_size, <anno>MinBinVHeapSize</anno>}</c></tag> <item> - <p><c><anno>MinBinVHeapSize</anno></c> is the minimum binary virtual heap size for the process.</p> + <p><c><anno>MinBinVHeapSize</anno></c> is the minimum binary virtual + heap size for the process.</p> </item> <tag><c>{monitored_by, <anno>Pids</anno>}</c></tag> <item> - <p>A list of pids that are monitoring the process (with + <p>A list of process identifiers monitoring the process (with <c>monitor/2</c>).</p> </item> <tag><c>{monitors, <anno>Monitors</anno>}</c></tag> <item> <p>A list of monitors (started by <c>monitor/2</c>) that are active for the process. For a local process - monitor or a remote process monitor by pid, the list item - is <c>{process, <anno>Pid</anno>}</c>, and for a remote process + monitor or a remote process monitor by a process + identifier, the list item is <c>{process, <anno>Pid</anno>}</c>. + For a remote process monitor by name, the list item is <c>{process, {<anno>RegName</anno>, <anno>Node</anno>}}</c>.</p> </item> - <tag><c>{priority, Level}</c></tag> + <tag><c>{priority, <anno>Level</anno>}</c></tag> <item> <p><c><anno>Level</anno></c> is the current priority level for - the process. For more information on priorities see - <seealso marker="#process_flag_priority">process_flag(priority, Level)</seealso>.</p> + the process. For more information on priorities, see + <seealso marker="#process_flag_priority">process_flag(priority, + Level)</seealso>.</p> </item> <tag><c>{reductions, <anno>Number</anno>}</c></tag> <item> @@ -3991,240 +4681,346 @@ os_prompt% </pre> </item> <tag><c>{sequential_trace_token, [] | <anno>SequentialTraceToken</anno>}</c></tag> <item> - <p><c><anno>SequentialTraceToken</anno></c> the sequential trace token for - the process. This <c><anno>InfoTuple</anno></c> may be changed or removed - without prior notice.</p> + <p><c><anno>SequentialTraceToken</anno></c> is the sequential trace + token for the process. This <c><anno>InfoTuple</anno></c> can be + changed or removed without prior notice.</p> </item> <tag><c>{stack_size, <anno>Size</anno>}</c></tag> <item> - <p><c><anno>Size</anno></c> is the stack size of the process in words.</p> + <p><c><anno>Size</anno></c> is the stack size, in words, + of the process.</p> </item> <tag><c>{status, <anno>Status</anno>}</c></tag> <item> - <p><c><anno>Status</anno></c> is the status of the process. <c><anno>Status</anno></c> - is <c>exiting</c>, <c>garbage_collecting</c>, - <c>waiting</c> (for a message), <c>running</c>, - <c>runnable</c> (ready to run, but another process is - running), or <c>suspended</c> (suspended on a "busy" port - or by the <c>erlang:suspend_process/[1,2]</c> BIF).</p> + <p><c><anno>Status</anno></c> is the status of the process and is one + of the following:</p> + <list type="bulleted"> + <item><c>exiting</c></item> + <item><c>garbage_collecting</c></item> + <item><c>waiting</c> (for a message)</item> + <item><c>running</c></item> + <item><c>runnable</c> (ready to run, but another process is + running)</item> + <item><c>suspended</c> (suspended on a "busy" port + or by the BIF <c>erlang:suspend_process/[1,2]</c>)</item> + </list> </item> <tag><c>{suspending, <anno>SuspendeeList</anno>}</c></tag> <item> - <p><c><anno>SuspendeeList</anno></c> is a list of <c>{<anno>Suspendee</anno>, - <anno>ActiveSuspendCount</anno>, <anno>OutstandingSuspendCount</anno>}</c> tuples. - <c><anno>Suspendee</anno></c> is the pid of a process that have been or is to - be suspended by the process identified by <c><anno>Pid</anno></c> via the - <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso> - BIF, or the - <seealso marker="#suspend_process/1">erlang:suspend_process/1</seealso> - BIF. <c><anno>ActiveSuspendCount</anno></c> is the number of times the - <c><anno>Suspendee</anno></c> has been suspended by <c><anno>Pid</anno></c>. + <p><c><anno>SuspendeeList</anno></c> is a list of + <c>{<anno>Suspendee</anno>, <anno>ActiveSuspendCount</anno>, + <anno>OutstandingSuspendCount</anno>}</c> tuples. + <c><anno>Suspendee</anno></c> is the process identifier of a + process that has been, or is to be, + suspended by the process identified by <c><anno>Pid</anno></c> + through one of the following BIFs:</p> + <list type="bulleted"> + <item> + <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso> + </item> + <item> + <seealso marker="#suspend_process/1">erlang:suspend_process/1</seealso> + </item> + </list> + <p><c><anno>ActiveSuspendCount</anno></c> is the number of + times <c><anno>Suspendee</anno></c> has been suspended by + <c><anno>Pid</anno></c>. <c><anno>OutstandingSuspendCount</anno></c> is the number of not yet - completed suspend requests sent by <c><anno>Pid</anno></c>. That is, - if <c><anno>ActiveSuspendCount</anno> =/= 0</c>, <c><anno>Suspendee</anno></c> is - currently in the suspended state, and if - <c><anno>OutstandingSuspendCount</anno> =/= 0</c> the <c>asynchronous</c> - option of <c>erlang:suspend_process/2</c> has been used and - the suspendee has not yet been suspended by <c><anno>Pid</anno></c>. - Note that the <c><anno>ActiveSuspendCount</anno></c> and - <c><anno>OutstandingSuspendCount</anno></c> are not the total suspend count - on <c><anno>Suspendee</anno></c>, only the parts contributed by <c>Pid</c>. - </p> + completed suspend requests sent by <c><anno>Pid</anno></c>, that is:</p> + <list type="bulleted"> + <item>If <c><anno>ActiveSuspendCount</anno> =/= 0</c>, + <c><anno>Suspendee</anno></c> is + currently in the suspended state. + </item> + <item>If <c><anno>OutstandingSuspendCount</anno> =/= 0</c>, option + <c>asynchronous</c> of <c>erlang:suspend_process/2</c> + has been used and the suspendee has not yet been + suspended by <c><anno>Pid</anno></c>. + </item> + </list> + <p>Notice that <c><anno>ActiveSuspendCount</anno></c> and + <c><anno>OutstandingSuspendCount</anno></c> are not the + total suspend count on <c><anno>Suspendee</anno></c>, + only the parts contributed by <c><anno>Pid</anno></c>.</p> </item> <tag><c>{total_heap_size, <anno>Size</anno>}</c></tag> <item> - <p><c><anno>Size</anno></c> is the total size in words of all heap - fragments of the process. This currently include the stack - of the process. - </p> + <p><c><anno>Size</anno></c> is the total size, in words, of all heap + fragments of the process. This includes the process stack.</p> </item> <tag><c>{trace, <anno>InternalTraceFlags</anno>}</c></tag> <item> - <p><c><anno>InternalTraceFlags</anno></c> is an integer representing - internal trace flag for this process. This <c><anno>InfoTuple</anno></c> - may be changed or removed without prior notice.</p> + <p><c><anno>InternalTraceFlags</anno></c> is an integer + representing the internal trace flag for this process. + This <c><anno>InfoTuple</anno></c> + can be changed or removed without prior notice.</p> </item> <tag><c>{trap_exit, <anno>Boolean</anno>}</c></tag> <item> - <p><c><anno>Boolean</anno></c> is <c>true</c> if the process is trapping - exits, otherwise it is <c>false</c>.</p> + <p><c><anno>Boolean</anno></c> is <c>true</c> if the process + is trapping exits, otherwise <c>false</c>.</p> </item> </taglist> - <p>Note however, that not all implementations support every one - of the above <c><anno>Item</anno></c>s.</p> - <p>Failure: <c>badarg</c> if <c><anno>Pid</anno></c> is not a local process, - or if <c><anno>Item</anno></c> is not a valid <c><anno>Item</anno></c>.</p> + <p>Notice that not all implementations support all + these <c><anno>Item</anno></c>s.</p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item>If <c><anno>Pid</anno></c> is not a local process.</item> + <tag><c>badarg</c></tag> + <item>If <c><anno>Item</anno></c> is an invalid item.</item> + </taglist> </desc> </func> + <func> <name name="processes" arity="0"/> - <fsummary>All processes</fsummary> + <fsummary>All processes.</fsummary> <desc> <p>Returns a list of process identifiers corresponding to - all the processes currently existing on the local node. - </p> - <p>Note that a process that is exiting, exists but is not alive, i.e., - <c>is_process_alive/1</c> will return <c>false</c> for a process - that is exiting, but its process identifier will be part - of the result returned from <c>processes/0</c>. - </p> + all the processes currently existing on the local node.</p> + <p>Notice that an exiting process exists, but is not alive. + That is, <c>is_process_alive/1</c> returns <c>false</c> + for an exiting process, but its process identifier is part + of the result returned from <c>processes/0</c>.</p> + <p>Example:</p> <pre> > <input>processes().</input> [<0.0.0>,<0.2.0>,<0.4.0>,<0.5.0>,<0.7.0>,<0.8.0>]</pre> </desc> </func> + <func> <name name="purge_module" arity="1"/> - <fsummary>Remove old code for a module</fsummary> + <fsummary>Removes old code for a module.</fsummary> <desc> - <p>Removes old code for <c><anno>Module</anno></c>. Before this BIF is used, - <c>erlang:check_process_code/2</c> should be called to check - that no processes are executing old code in the module.</p> + <p>Removes old code for <c><anno>Module</anno></c>. + Before this BIF is used, + <c>erlang:check_process_code/2</c> is to be called to check + that no processes execute old code in the module.</p> <warning> <p>This BIF is intended for the code server (see - <seealso marker="kernel:code">code(3)</seealso>) and should not be - used elsewhere.</p> + <seealso marker="kernel:code">code(3)</seealso>) + and is not to be used elsewhere.</p> </warning> <p>Failure: <c>badarg</c> if there is no old code for <c><anno>Module</anno></c>.</p> </desc> </func> + <func> <name name="put" arity="2"/> - <fsummary>Add a new value to the process dictionary</fsummary> - <desc> - <p>Adds a new <c><anno>Key</anno></c> to the process dictionary, associated - with the value <c><anno>Val</anno></c>, and returns <c>undefined</c>. If - <c><anno>Key</anno></c> already exists, the old value is deleted and - replaced by <c><anno>Val</anno></c> and the function returns the old value.</p> - <note> - <p>The values stored when <c>put</c> is evaluated within - the scope of a <c>catch</c> will not be retracted if a - <c>throw</c> is evaluated, or if an error occurs.</p> - </note> + <fsummary>Adds a new value to the process dictionary.</fsummary> + <desc> + <p>Adds a new <c><anno>Key</anno></c> to the process dictionary, + associated with the value <c><anno>Val</anno></c>, and returns + <c>undefined</c>. If <c><anno>Key</anno></c> exists, the old + value is deleted and replaced by <c><anno>Val</anno></c>, and + the function returns the old value.</p> + <p>Example:</p> <pre> > <input>X = put(name, walrus), Y = put(name, carpenter),</input> <input>Z = get(name),</input> <input>{X, Y, Z}.</input> {undefined,walrus,carpenter}</pre> + <note> + <p>The values stored when <c>put</c> is evaluated within + the scope of a <c>catch</c> are not retracted if a + <c>throw</c> is evaluated, or if an error occurs.</p> + </note> </desc> </func> + <func> <name name="raise" arity="3"/> + <fsummary>Stops execution with an exception of given class, reason, and call stack backtrace.</fsummary> <type name="raise_stacktrace"/> - <fsummary>Stop execution with an exception of given class, reason and call stack backtrace</fsummary> <desc> <p>Stops the execution of the calling process with an - exception of given class, reason and call stack backtrace + exception of given class, reason, and call stack backtrace (<em>stacktrace</em>).</p> <warning> - <p>This BIF is intended for debugging and for use in - the Erlang operating system. In general, it should - be avoided in applications, unless you know - very well what you are doing.</p> + <p>This BIF is intended for debugging. Avoid to use it in applications, + unless you really know what you are doing.</p> </warning> - <p><c><anno>Class</anno></c> is one of <c>error</c>, <c>exit</c> or - <c>throw</c>, so if it were not for the stacktrace - <c>erlang:raise(<anno>Class</anno>, <anno>Reason</anno>, <anno>Stacktrace</anno>)</c> is - equivalent to <c>erlang:<anno>Class</anno>(<anno>Reason</anno>)</c>. - <c><anno>Reason</anno></c> is any term and <c><anno>Stacktrace</anno></c> is a list as - returned from <c>get_stacktrace()</c>, that is a list of - 4-tuples <c>{Module, Function, Arity | Args, - Location}</c> where <c>Module</c> and <c>Function</c> - are atoms and the third element is an integer arity or an - argument list. The stacktrace may also contain <c>{Fun, - Args, Location}</c> tuples where - <c>Fun</c> is a local fun and <c>Args</c> is an argument list.</p> - <p>The <c>Location</c> element at the end is optional. + <p><c><anno>Class</anno></c> is <c>error</c>, <c>exit</c>, or + <c>throw</c>. So, if it were not for the stacktrace, + <c>erlang:raise(<anno>Class</anno>, <anno>Reason</anno>, + <anno>Stacktrace</anno>)</c> is + equivalent to <c>erlang:<anno>Class</anno>(<anno>Reason</anno>)</c>.</p> + <p><c><anno>Reason</anno></c> is any term. + <c><anno>Stacktrace</anno></c> is a list as + returned from <c>get_stacktrace()</c>, that is, a list of + four-tuples <c>{Module, Function, Arity | Args, + Location}</c>, where <c>Module</c> and <c>Function</c> + are atoms, and the third element is an integer arity or an + argument list. The stacktrace can also contain <c>{Fun, + Args, Location}</c> tuples, where <c>Fun</c> is a local + fun and <c>Args</c> is an argument list.</p> + <p>Element <c>Location</c> at the end is optional. Omitting it is equivalent to specifying an empty list.</p> <p>The stacktrace is used as the exception stacktrace for the - calling process; it will be truncated to the current + calling process; it is truncated to the current maximum stacktrace depth.</p> - <p>Because evaluating this function causes the process to - terminate, it has no return value - unless the arguments are - invalid, in which case the function <em>returns the error reason</em>, that is <c>badarg</c>. If you want to be - really sure not to return you can call - <c>error(erlang:raise(<anno>Class</anno>, <anno>Reason</anno>, <anno>Stacktrace</anno>))</c> + <p>Since evaluating this function causes the process to + terminate, it has no return value unless the arguments are + invalid, in which case the function <em>returns the error + reason</em> <c>badarg</c>. If you want to be + sure not to return, you can call + <c>error(erlang:raise(<anno>Class</anno>, <anno>Reason</anno>, + <anno>Stacktrace</anno>))</c> and hope to distinguish exceptions later.</p> </desc> </func> + <func> - <name name="read_timer" arity="1"/> - <fsummary>Number of milliseconds remaining for a timer</fsummary> - <desc> - <p><c><anno>TimerRef</anno></c> is a timer reference returned by - <seealso marker="#send_after/3">erlang:send_after/3</seealso> - or - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>. - If the timer is active, the function returns the time in - milliseconds left until the timer will expire, otherwise - <c>false</c> (which means that <c><anno>TimerRef</anno></c> was never a - timer, that it has been cancelled, or that it has already - delivered its message).</p> + <name name="read_timer" arity="2"/> + <fsummary>Reads the state of a timer.</fsummary> + <desc> + <p> + Read the state of a timer that has been created by either + <seealso marker="#start_timer/4"><c>erlang:start_timer()</c></seealso>, + or <seealso marker="#send_after/4"><c>erlang:send_after()</c></seealso>. + <c><anno>TimerRef</anno></c> identifies the timer, and + was returned by the BIF that created the timer. + </p> + <p>Available <c><anno>Option</anno>s</c>:</p> + <taglist> + <tag><c>{async, Async}</c></tag> + <item> + <p> + Asynchronous request for state information. <c>Async</c> + defaults to <c>false</c> which will cause the operation + to be performed synchronously. In this case, the <c>Result</c> + is returned by <c>erlang:read_timer()</c>. When + <c>Async</c> is <c>true</c>, <c>erlang:read_timer()</c> + sends an asynchronous request for the state information + to the timer service that manages the timer, and then returns + <c>ok</c>. A message on the format <c>{read_timer, + <anno>TimerRef</anno>, <anno>Result</anno>}</c> is + sent to the caller of <c>erlang:read_timer()</c> when the + operation has been processed. + </p> + </item> + </taglist> + <p> + More <c><anno>Option</anno></c>s may be added in the future. + </p> + <p> + If <c><anno>Result</anno></c> is an integer, it represents the + time in milli-seconds left until the timer expires.</p> + <p> + If <c><anno>Result</anno></c> is <c>false</c>, a + timer corresponding to <c><anno>TimerRef</anno></c> could not + be found. This can be because the timer had expired, + it had been canceled, or because <c><anno>TimerRef</anno></c> + never has corresponded to a timer. Even if the timer has expired, + it does not tell you whether or not the timeout message has + arrived at its destination yet. + </p> + <note> + <p> + The timer service that manages the timer may be co-located + with another scheduler than the scheduler that the calling + process is executing on. If this is the case, communication + with the timer service takes much longer time than if it + is located locally. If the calling process is in critical + path, and can do other things while waiting for the result + of this operation, you want to use option <c>{async, true}</c>. + If using option <c>{async, false}</c>, the calling + process will be blocked until the operation has been + performed. + </p> + </note> <p>See also - <seealso marker="#send_after/3">erlang:send_after/3</seealso>, - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>, + <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>, + <seealso marker="#start_timer/4"><c>erlang:start_timer/4</c></seealso>, and - <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>.</p> + <seealso marker="#cancel_timer/2"><c>erlang:cancel_timer/2</c></seealso>.</p> </desc> </func> <func> + <name name="read_timer" arity="1"/> + <fsummary>Reads the state of a timer.</fsummary> + <desc> + <p>Read the state of a timer. The same as calling + <seealso marker="#read_timer/2"><c>erlang:read_timer(TimerRef, + [])</c></seealso>.</p> + </desc> + </func> + + <func> <name name="ref_to_list" arity="1"/> - <fsummary>Text representation of a reference</fsummary> + <fsummary>Text representation of a reference.</fsummary> <desc> - <p>Returns a string which corresponds to the text + <p>Returns a string corresponding to the text representation of <c><anno>Ref</anno></c>.</p> <warning> - <p>This BIF is intended for debugging and for use in - the Erlang operating system. It should not be used in - application programs.</p> + <p>This BIF is intended for debugging and is not to be used + in application programs.</p> </warning> </desc> </func> + <func> <name name="register" arity="2"/> - <fsummary>Register a name for a pid (or port)</fsummary> + <fsummary>Registers a name for a pid (or port).</fsummary> <desc> - <p>Associates the name <c><anno>RegName</anno></c> with a pid or a port - identifier. <c><anno>RegName</anno></c>, which must be an atom, can be used - instead of the pid / port identifier in the send operator + <p>Associates the name <c><anno>RegName</anno></c> with a process + identifier (pid) or a port identifier. + <c><anno>RegName</anno></c>, which must be an atom, can be used + instead of the pid or port identifier in send operator (<c><anno>RegName</anno> ! Message</c>).</p> + <p>Example:</p> <pre> > <input>register(db, Pid).</input> true</pre> - <p>Failure: <c>badarg</c> if <c><anno>PidOrPort</anno></c> is not an existing, - local process or port, if <c><anno>RegName</anno></c> is already in use, - if the process or port is already registered (already has a - name), or if <c><anno>RegName</anno></c> is the atom <c>undefined</c>.</p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item>If <c><anno>PidOrPort</anno></c> is not an existing local + process or port.</item> + <tag><c>badarg</c></tag> + <item>If <c><anno>RegName</anno></c> is already in use.</item> + <tag><c>badarg</c></tag> + <item>If the process or port is already registered + (already has a name).</item> + <tag><c>badarg</c></tag> + <item>If <c><anno>RegName</anno></c> is the atom + <c>undefined</c>.</item> + </taglist> </desc> </func> + <func> <name name="registered" arity="0"/> - <fsummary>All registered names</fsummary> + <fsummary>All registered names.</fsummary> <desc> - <p>Returns a list of names which have been registered using - <seealso marker="#register/2">register/2</seealso>.</p> + <p>Returns a list of names that have been registered using + <seealso marker="#register/2">register/2</seealso>, for + example:</p> <pre> > <input>registered().</input> [code_server, file_server, init, user, my_db]</pre> </desc> </func> + <func> <name name="resume_process" arity="1"/> - <fsummary>Resume a suspended process</fsummary> + <fsummary>Resumes a suspended process.</fsummary> <desc> <p>Decreases the suspend count on the process identified by - <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c> should previously have been - suspended via - <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso>, + <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c> + is previously to have been suspended through + <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso> or <seealso marker="#suspend_process/1">erlang:suspend_process/1</seealso> - by the process calling <c>erlang:resume_process(<anno>Suspendee</anno>)</c>. When - the suspend count on <c><anno>Suspendee</anno></c> reach zero, <c><anno>Suspendee</anno></c> - will be resumed, i.e., the state of the <c>Suspendee</c> is changed - from suspended into the state <c><anno>Suspendee</anno></c> was in before it was - suspended. - </p> + by the process calling + <c>erlang:resume_process(<anno>Suspendee</anno>)</c>. When the + suspend count on <c><anno>Suspendee</anno></c> reaches zero, + <c><anno>Suspendee</anno></c> is resumed, that is, its state + is changed from suspended into the state it had before it was + suspended.</p> <warning> <p>This BIF is intended for debugging only.</p> </warning> @@ -4232,7 +5028,7 @@ true</pre> <taglist> <tag><c>badarg</c></tag> <item> - If <c><anno>Suspendee</anno></c> isn't a process identifier. + If <c><anno>Suspendee</anno></c> is not a process identifier. </item> <tag><c>badarg</c></tag> <item> @@ -4242,58 +5038,65 @@ true</pre> </item> <tag><c>badarg</c></tag> <item> - If the process identified by <c><anno>Suspendee</anno></c> is not alive. + If the process identified by <c><anno>Suspendee</anno></c> + is not alive. </item> </taglist> </desc> </func> + <func> <name name="round" arity="1"/> - <fsummary>Return an integer by rounding a number</fsummary> + <fsummary>Returns an integer by rounding a number.</fsummary> <desc> - <p>Returns an integer by rounding <c><anno>Number</anno></c>.</p> + <p>Returns an integer by rounding <c><anno>Number</anno></c>, + for example:</p> <pre> -> <input>round(5.5).</input> +<input>round(5.5).</input> 6</pre> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="self" arity="0"/> - <fsummary>Pid of the calling process</fsummary> + <fsummary>Returns pid of the calling process.</fsummary> <desc> - <p>Returns the pid (process identifier) of the calling process.</p> + <p>Returns the process identifier of the calling process, for + example:</p> <pre> > <input>self().</input> <0.26.0></pre> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="send" arity="2"/> - <fsummary>Send a message</fsummary> + <fsummary>Sends a message.</fsummary> <type name="dst"/> <desc> - <p>Sends a message and returns <c><anno>Msg</anno></c>. This is the same as - <c><anno>Dest</anno> ! <anno>Msg</anno></c>.</p> - <p><c><anno>Dest</anno></c> may be a remote or local pid, a (local) port, a - locally registered name, or a tuple <c>{<anno>RegName</anno>, <anno>Node</anno>}</c> + <p>Sends a message and returns <c><anno>Msg</anno></c>. This + is the same as <c><anno>Dest</anno> ! <anno>Msg</anno></c>.</p> + <p><c><anno>Dest</anno></c> can be a remote or local process identifier, + a (local) port, a locally registered name, or a tuple + <c>{<anno>RegName</anno>, <anno>Node</anno>}</c> for a registered name at another node.</p> </desc> </func> + <func> <name name="send" arity="3"/> + <fsummary>Sends a message conditionally.</fsummary> <type name="dst"/> - <fsummary>Send a message conditionally</fsummary> - <desc> - <p>Sends a message and returns <c>ok</c>, or does not send - the message but returns something else (see below). Otherwise - the same as - <seealso marker="#send/2">erlang:send/2</seealso>. See - also - <seealso marker="#send_nosuspend/2">erlang:send_nosuspend/2,3</seealso>. - for more detailed explanation and warnings.</p> - <p>The possible options are:</p> + <desc> + <p>Either sends a message and returns <c>ok</c>, or does not send + the message but returns something else (see the following). + Otherwise the same as + <seealso marker="#send/2">erlang:send/2</seealso>. + For more detailed explanation and warnings, see + <seealso marker="#send_nosuspend/2">erlang:send_nosuspend/2,3</seealso>.</p> + <p>The options are as follows:</p> <taglist> <tag><c>nosuspend</c></tag> <item> @@ -4303,319 +5106,366 @@ true</pre> <tag><c>noconnect</c></tag> <item> <p>If the destination node would have to be auto-connected - before doing the send, <c>noconnect</c> is returned + to do the send, <c>noconnect</c> is returned instead.</p> </item> </taglist> <warning> - <p>As with <c>erlang:send_nosuspend/2,3</c>: Use with extreme - care!</p> + <p>As with <c>erlang:send_nosuspend/2,3</c>: use with extreme + care.</p> </warning> </desc> </func> + <func> - <name name="send_after" arity="3"/> - <type_desc variable="Time">0 <= Time <= 4294967295</type_desc> + <name name="send_after" arity="4"/> <fsummary>Start a timer</fsummary> <desc> - <p>Starts a timer which will send the message <c>Msg</c> - to <c><anno>Dest</anno></c> after <c><anno>Time</anno></c> milliseconds.</p> - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c> it has to be a <c>pid()</c> of a local process, dead or alive.</p> - <p>The <c><anno>Time</anno></c> value can, in the current implementation, not be greater than 4294967295.</p> - <p>If <c><anno>Dest</anno></c> is an <c>atom()</c>, it is supposed to be the name of - a registered process. The process referred to by the name is - looked up at the time of delivery. No error is given if - the name does not refer to a process.</p> - - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will be automatically - canceled if the process referred to by the <c>pid()</c> is not alive, - or when the process exits. This feature was introduced in - erts version 5.4.11. Note that timers will not be - automatically canceled when <c><anno>Dest</anno></c> is an <c>atom</c>.</p> - <p>See also - <seealso marker="#start_timer/3">erlang:start_timer/3</seealso>, - <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>, - and - <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p> - <p>Failure: <c>badarg</c> if the arguments does not satisfy - the requirements specified above.</p> + <p> + Starts a timer. When the timer expires, the message + <c><anno>Msg</anno></c> is sent to the process + identified by <c><anno>Dest</anno></c>. Apart from + the format of the timeout message, + <c>erlang:send_after/4</c> works exactly as + <seealso marker="#start_timer/4"><c>erlang:start_timer/4</c></seealso>.</p> </desc> </func> <func> + <name name="send_after" arity="3"/> + <fsummary>Starts a timer.</fsummary> + <desc> + <p>Starts a timer. The same as calling + <seealso marker="#send_after/4"><c>erlang:send_after(<anno>Time</anno>, + <anno>Dest</anno>, <anno>Msg</anno>, [])</c></seealso>.</p> + </desc> + </func> + + <func> <name name="send_nosuspend" arity="2"/> - <fsummary>Try to send a message without ever blocking</fsummary> + <fsummary>Tries to send a message without ever blocking.</fsummary> <type name="dst"/> <desc> <p>The same as - <seealso marker="#send/3">erlang:send(<anno>Dest</anno>, <anno>Msg</anno>, [nosuspend])</seealso>, but returns <c>true</c> if + <seealso marker="#send/3">erlang:send(<anno>Dest</anno>, + <anno>Msg</anno>, [nosuspend])</seealso>, + but returns <c>true</c> if the message was sent and <c>false</c> if the message was not sent because the sender would have had to be suspended.</p> - <p>This function is intended for send operations towards an + <p>This function is intended for send operations to an unreliable remote node without ever blocking the sending (Erlang) process. If the connection to the remote node (usually not a real Erlang node, but a node written in C or - Java) is overloaded, this function <em>will not send the message</em> but return <c>false</c> instead.</p> - <p>The same happens, if <c><anno>Dest</anno></c> refers to a local port that - is busy. For all other destinations (allowed for the ordinary - send operator <c>'!'</c>) this function sends the message and + Java) is overloaded, this function <em>does not send the message</em> + and returns <c>false</c>.</p> + <p>The same occurs if <c><anno>Dest</anno></c> refers to a local port + that is busy. For all other destinations (allowed for the ordinary + send operator <c>'!'</c>), this function sends the message and returns <c>true</c>.</p> - <p>This function is only to be used in very rare circumstances + <p>This function is only to be used in rare circumstances where a process communicates with Erlang nodes that can - disappear without any trace causing the TCP buffers and - the drivers queue to be over-full before the node will actually - be shut down (due to tick timeouts) by <c>net_kernel</c>. The - normal reaction to take when this happens is some kind of + disappear without any trace, causing the TCP buffers and + the drivers queue to be over-full before the node is + shut down (because of tick time-outs) by <c>net_kernel</c>. + The normal reaction to take when this occurs is some kind of premature shutdown of the other node.</p> - <p>Note that ignoring the return value from this function would - result in <em>unreliable</em> message passing, which is + <p>Notice that ignoring the return value from this function would + result in an <em>unreliable</em> message passing, which is contradictory to the Erlang programming model. The message is <em>not</em> sent if this function returns <c>false</c>.</p> - <p>Note also that in many systems, transient states of + <p>In many systems, transient states of overloaded queues are normal. The fact that this function - returns <c>false</c> does not in any way mean that the other + returns <c>false</c> does not mean that the other node is guaranteed to be non-responsive, it could be a - temporary overload. Also a return value of <c>true</c> does - only mean that the message could be sent on the (TCP) channel - without blocking, the message is not guaranteed to have - arrived at the remote node. Also in the case of a disconnected + temporary overload. Also, a return value of <c>true</c> does + only mean that the message can be sent on the (TCP) channel + without blocking, the message is not guaranteed to + arrive at the remote node. For a disconnected non-responsive node, the return value is <c>true</c> (mimics - the behaviour of the <c>!</c> operator). The expected - behaviour as well as the actions to take when the function - returns <c>false</c> are application and hardware specific.</p> + the behavior of operator <c>!</c>). The expected + behavior and the actions to take when the function + returns <c>false</c> are application- and hardware-specific.</p> <warning> - <p>Use with extreme care!</p> + <p>Use with extreme care.</p> </warning> </desc> </func> + <func> <name name="send_nosuspend" arity="3"/> - <fsummary>Try to send a message without ever blocking</fsummary> + <fsummary>Tries to send a message without ever blocking.</fsummary> <type name="dst"/> <desc> <p>The same as - <seealso marker="#send/3">erlang:send(<anno>Dest</anno>, <anno>Msg</anno>, [nosuspend | <anno>Options</anno>])</seealso>, - but with boolean return value.</p> + <seealso marker="#send/3">erlang:send(<anno>Dest</anno>, + <anno>Msg</anno>, [nosuspend | <anno>Options</anno>])</seealso>, + but with a Boolean return value.</p> <p>This function behaves like - <seealso marker="#send_nosuspend/2">erlang:send_nosuspend/2)</seealso>, - but takes a third parameter, a list of options. The only - currently implemented option is <c>noconnect</c>. The option - <c>noconnect</c> makes the function return <c>false</c> if + <seealso marker="#send_nosuspend/2">erlang:send_nosuspend/2</seealso>, + but takes a third parameter, a list of options. + The only option is <c>noconnect</c>, which + makes the function return <c>false</c> if the remote node is not currently reachable by the local - node. The normal behaviour is to try to connect to the node, - which may stall the process for a shorter period. The use of - the <c>noconnect</c> option makes it possible to be - absolutely sure not to get even the slightest delay when + node. The normal behavior is to try to connect to the node, + which can stall the process during a short period. The use of + option <c>noconnect</c> makes it possible to be + sure not to get the slightest delay when sending to a remote process. This is especially useful when - communicating with nodes who expect to always be - the connecting part (i.e. nodes written in C or Java).</p> + communicating with nodes that expect to always be + the connecting part (that is, nodes written in C or Java).</p> <p>Whenever the function returns <c>false</c> (either when a suspend would occur or when <c>noconnect</c> was specified and the node was not already connected), the message is guaranteed <em>not</em> to have been sent.</p> <warning> - <p>Use with extreme care!</p> + <p>Use with extreme care.</p> </warning> </desc> </func> + <func> <name name="set_cookie" arity="2"/> - <fsummary>Set the magic cookie of a node</fsummary> + <fsummary>Sets the magic cookie of a node.</fsummary> <desc> <p>Sets the magic cookie of <c><anno>Node</anno></c> to the atom - <c><anno>Cookie</anno></c>. If <c><anno>Node</anno></c> is the local node, the function + <c><anno>Cookie</anno></c>. If <c><anno>Node</anno></c> is the + local node, the function also sets the cookie of all other unknown nodes to - <c><anno>Cookie</anno></c> (see - <seealso marker="doc/reference_manual:distributed">Distributed Erlang</seealso> in the Erlang Reference Manual).</p> + <c><anno>Cookie</anno></c> (see Section + <seealso marker="doc/reference_manual:distributed">Distributed Erlang</seealso> + in the Erlang Reference Manual in System Documentation).</p> <p>Failure: <c>function_clause</c> if the local node is not alive.</p> </desc> </func> + <func> <name name="setelement" arity="3"/> - <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno>)</type_desc> - <fsummary>Set Nth element of a tuple</fsummary> + <fsummary>Sets the Nth element of a tuple.</fsummary> + <type_desc variable="Index">1..tuple_size(<anno>Tuple1</anno></type_desc> <desc> - <p>Returns a tuple which is a copy of the argument <c><anno>Tuple1</anno></c> - with the element given by the integer argument <c><anno>Index</anno></c> + <p>Returns a tuple that is a copy of argument + <c><anno>Tuple1</anno></c> + with the element given by integer argument + <c><anno>Index</anno></c> (the first element is the element with index 1) replaced by - the argument <c><anno>Value</anno></c>.</p> + argument <c><anno>Value</anno></c>, for example:</p> <pre> > <input>setelement(2, {10, green, bottles}, red).</input> {10,red,bottles}</pre> </desc> </func> + <func> <name name="size" arity="1"/> - <fsummary>Size of a tuple or binary</fsummary> + <fsummary>Size of a tuple or binary.</fsummary> <desc> - <p>Returns an integer which is the size of the argument - <c><anno>Item</anno></c>, which must be either a tuple or a binary.</p> + <p>Returns the number of elements in a tuple or the number of + bytes in a binary or bitstring, for example:</p> <pre> > <input>size({morni, mulle, bwange}).</input> -3</pre> +3 +> <input>size(<<11, 22, 33>>).</input> +3 +</pre> + <p>For bitstrings the number of whole bytes is returned. That is, if the number of bits + in the bitstring is not divisible by 8, the resulting + number of bytes is rounded <em>down</em>.</p> <p>Allowed in guard tests.</p> + <p>See also + <seealso marker="#tuple_size/1"><c>tuple_size/1</c></seealso>, + <seealso marker="#byte_size/1"><c>byte_size/1</c></seealso> + and + <seealso marker="#bit_size/1"><c>bit_size/1</c></seealso>.</p> </desc> </func> + <func> <name name="spawn" arity="1"/> - <fsummary>Create a new process with a fun as entry point</fsummary> + <fsummary>Creates a new process with a fun as entry point.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list <c>[]</c>. Otherwise works - like <seealso marker="#spawn/3">spawn/3</seealso>.</p> + <p>Returns the process identifier of a new process started by the + application of <c><anno>Fun</anno></c> to the empty list + <c>[]</c>. Otherwise + works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn" arity="2"/> - <fsummary>Create a new process with a fun as entry point on a given node</fsummary> + <fsummary>Creates a new process with a fun as entry point on a given node.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list <c>[]</c> on <c><anno>Node</anno></c>. If - <c><anno>Node</anno></c> does not exist, a useless pid is returned. - Otherwise works like + <p>Returns the process identifier of a new process started + by the application of <c><anno>Fun</anno></c> to the + empty list <c>[]</c> on <c><anno>Node</anno></c>. If + <c><anno>Node</anno></c> does not exist, a useless pid is + returned. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn" arity="3"/> - <fsummary>Create a new process with a function as entry point</fsummary> - <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c>. The new process - created will be placed in the system scheduler queue and be - run some time later.</p> - <p><c>error_handler:undefined_function(<anno>Module</anno>, <anno>Function</anno>, <anno>Args</anno>)</c> is evaluated by the new process if - <c><anno>Module</anno>:<anno>Function</anno>/Arity</c> does not exist (where - <c>Arity</c> is the length of <c><anno>Args</anno></c>). The error handler + <fsummary>Creates a new process with a function as entry point.</fsummary> + <desc> + <p>Returns the process identifier of a new process started by + the application of <c><anno>Module</anno>:<anno>Function</anno></c> + to <c><anno>Args</anno></c>.</p> + <p><c>error_handler:undefined_function(<anno>Module</anno>, + <anno>Function</anno>, <anno>Args</anno>)</c> + is evaluated by the new process if + <c><anno>Module</anno>:<anno>Function</anno>/Arity</c> + does not exist (where <c>Arity</c> is the length of + <c><anno>Args</anno></c>). The error handler can be redefined (see <seealso marker="#process_flag/2">process_flag/2</seealso>). If <c>error_handler</c> is undefined, or the user has - redefined the default <c>error_handler</c> its replacement is - undefined, a failure with the reason <c>undef</c> will occur.</p> + redefined the default <c>error_handler</c> and its replacement is + undefined, a failure with reason <c>undef</c> occurs.</p> + <p>Example:</p> <pre> > <input>spawn(speed, regulator, [high_speed, thin_cut]).</input> <0.13.1></pre> </desc> </func> + <func> <name name="spawn" arity="4"/> - <fsummary>Create a new process with a function as entry point on a given node</fsummary> + <fsummary>Creates a new process with a function as entry point on a given node.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c> on <c>Node</c>. If - <c><anno>Node</anno></c> does not exists, a useless pid is returned. + <p>Returns the process identifier (pid) of a new process started + by the application + of <c><anno>Module</anno>:<anno>Function</anno></c> + to <c><anno>Args</anno></c> on <c><anno>Node</anno></c>. If + <c><anno>Node</anno></c> does not exist, a useless pid is returned. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_link" arity="1"/> - <fsummary>Create and link to a new process with a fun as entry point</fsummary> + <fsummary>Creates and links to a new process with a fun as entry point.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list []. A link is created between + <p>Returns the process identifier of a new process started by + the application of <c><anno>Fun</anno></c> to the empty list + <c>[]</c>. A link is created between the calling process and the new process, atomically. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_link" arity="2"/> - <fsummary>Create and link to a new process with a fun as entry point on a specified node</fsummary> + <fsummary>Creates and links to a new process with a fun as entry point on a specified node.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list [] on <c><anno>Node</anno></c>. A link is + <p>Returns the process identifier (pid) of a new process started + by the application of <c><anno>Fun</anno></c> to the empty + list <c>[]</c> on <c><anno>Node</anno></c>. A link is created between the calling process and the new process, - atomically. If <c><anno>Node</anno></c> does not exist, a useless pid is - returned (and due to the link, an exit signal with exit - reason <c>noconnection</c> will be received). Otherwise works - like <seealso marker="#spawn/3">spawn/3</seealso>.</p> + atomically. If <c><anno>Node</anno></c> does not exist, + a useless pid is returned and an exit signal with + reason <c>noconnection</c> is sent to the calling + process. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_link" arity="3"/> - <fsummary>Create and link to a new process with a function as entry point</fsummary> + <fsummary>Creates and links to a new process with a function as entry point.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c>. A link is created + <p>Returns the process identifier of a new process started by + the application of <c><anno>Module</anno>:<anno>Function</anno></c> + to <c><anno>Args</anno></c>. A link is created between the calling process and the new process, atomically. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_link" arity="4"/> - <fsummary>Create and link to a new process with a function as entry point on a given node</fsummary> + <fsummary>Creates and links to a new process with a function as entry point on a given node.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c> on <c>Node</c>. A + <p>Returns the process identifier (pid) of a new process + started by the application + of <c><anno>Module</anno>:<anno>Function</anno></c> + to <c><anno>Args</anno></c> on <c><anno>Node</anno></c>. A link is created between the calling process and the new - process, atomically. If <c><anno>Node</anno></c> does not exist, a useless - pid is returned (and due to the link, an exit signal with exit - reason <c>noconnection</c> will be received). Otherwise works - like <seealso marker="#spawn/3">spawn/3</seealso>.</p> + process, atomically. If <c><anno>Node</anno></c> does + not exist, a useless pid is returned and an exit signal with + reason <c>noconnection</c> is sent to the calling + process. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_monitor" arity="1"/> - <fsummary>Create and monitor a new process with a fun as entry point</fsummary> + <fsummary>Creates and monitors a new process with a fun as entry point.</fsummary> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list [] and reference for a monitor - created to the new process. + <p>Returns the process identifier of a new process, started by + the application of <c><anno>Fun</anno></c> to the empty list + <c>[]</c>, + and a reference for a monitor created to the new process. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_monitor" arity="3"/> - <fsummary>Create and monitor a new process with a function as entry point</fsummary> + <fsummary>Creates and monitors a new process with a function as entry point.</fsummary> <desc> <p>A new process is started by the application - of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c>, and the process is - monitored at the same time. Returns the pid and a reference - for the monitor. - Otherwise works like + of <c><anno>Module</anno>:<anno>Function</anno></c> + to <c><anno>Args</anno></c>. The process is + monitored at the same time. Returns the process identifier + and a reference for the monitor. Otherwise works like <seealso marker="#spawn/3">spawn/3</seealso>.</p> </desc> </func> + <func> <name name="spawn_opt" arity="2"/> - <type name="priority_level" /> - <fsummary>Create a new process with a fun as entry point</fsummary> + <fsummary>Creates a new process with a fun as entry point.</fsummary> + <type name="priority_level"/> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list <c>[]</c>. Otherwise - works like + <p>Returns the process identifier (pid) of a new process + started by the application of <c><anno>Fun</anno></c> + to the empty list <c>[]</c>. Otherwise works like <seealso marker="#spawn_opt/4">spawn_opt/4</seealso>.</p> - <p>If the option <c>monitor</c> is given, the newly created - process will be monitored and both the pid and reference for - the monitor will be returned.</p> + <p>If option <c>monitor</c> is given, the newly created + process is monitored, and both the pid and reference for + the monitor is returned.</p> </desc> </func> + <func> <name name="spawn_opt" arity="3"/> - <type name="priority_level" /> - <fsummary>Create a new process with a fun as entry point on a given node</fsummary> + <fsummary>Creates a new process with a fun as entry point on a given node.</fsummary> + <type name="priority_level"/> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Fun</anno></c> to the empty list <c>[]</c> on <c><anno>Node</anno></c>. If - <c><anno>Node</anno></c> does not exist, a useless pid is returned. - Otherwise works like + <p>Returns the process identifier (pid) of a new process started + by the application of <c><anno>Fun</anno></c> to the + empty list <c>[]</c> on <c><anno>Node</anno></c>. If + <c><anno>Node</anno></c> does not exist, a useless pid is + returned. Otherwise works like <seealso marker="#spawn_opt/4">spawn_opt/4</seealso>.</p> </desc> </func> + <func> <name name="spawn_opt" arity="4"/> - <type name="priority_level" /> - <fsummary>Create a new process with a function as entry point</fsummary> + <fsummary>Creates a new process with a function as entry point.</fsummary> + <type name="priority_level"/> <desc> - <p>Works exactly like + <p>Works as <seealso marker="#spawn/3">spawn/3</seealso>, except that an extra option list is given when creating the process.</p> - <p>If the option <c>monitor</c> is given, the newly created - process will be monitored and both the pid and reference for - the monitor will be returned.</p> + <p>If option <c>monitor</c> is given, the newly created + process is monitored, and both the pid and reference for + the monitor is returned.</p> + <p>The options are as follows:</p> <taglist> <tag><c>link</c></tag> <item> @@ -4624,110 +5474,123 @@ true</pre> </item> <tag><c>monitor</c></tag> <item> - <p>Monitor the new process (just like + <p>Monitors the new process (like <seealso marker="#monitor/2">monitor/2</seealso> does).</p> </item> - <tag><c>{priority, <anno>Level</anno>}</c></tag> + <tag><c>{priority, <anno>Level</anno></c></tag> <item> <p>Sets the priority of the new process. Equivalent to executing - <seealso marker="#process_flag_priority">process_flag(priority, <anno>Level</anno>)</seealso> in the start function of the new process, - except that the priority will be set before the process is - selected for execution for the first time. For more information - on priorities see - <seealso marker="#process_flag_priority">process_flag(priority, Level)</seealso>.</p> + <seealso marker="#process_flag_priority">process_flag(priority, + <anno>Level</anno>)</seealso> + in the start function of the new process, + except that the priority is set before the process is + selected for execution for the first time. For more + information on priorities, see + <seealso marker="#process_flag_priority">process_flag(priority, + <anno>Level</anno>)</seealso>.</p> </item> <tag><c>{fullsweep_after, <anno>Number</anno>}</c></tag> <item> - <p>This option is only useful for performance tuning. - In general, you should not use this option unless you - know that there is problem with execution times and/or - memory consumption, and you should measure to make sure - that the option improved matters. - </p> + <p>Useful only for performance tuning. Do not use this + option unless you + know that there is problem with execution times or + memory consumption, and ensure + that the option improves matters.</p> <p>The Erlang runtime system uses a generational garbage collection scheme, using an "old heap" for data that has survived at least one garbage collection. When there is no more room on the old heap, a fullsweep garbage - collection will be done.</p> - <p>The <c>fullsweep_after</c> option makes it possible to + collection is done.</p> + <p>Option <c>fullsweep_after</c> makes it possible to specify the maximum number of generational collections - before forcing a fullsweep even if there is still room on - the old heap. Setting the number to zero effectively - disables the general collection algorithm, meaning that + before forcing a fullsweep, even if there is room on + the old heap. Setting the number to zero + disables the general collection algorithm, that is, all live data is copied at every garbage collection.</p> - <p>Here are a few cases when it could be useful to change - <c>fullsweep_after</c>. Firstly, if binaries that are no - longer used should be thrown away as soon as possible. - (Set <c><anno>Number</anno></c> to zero.) Secondly, a process that - mostly have short-lived data will be fullsweeped seldom - or never, meaning that the old heap will contain mostly - garbage. To ensure a fullsweep once in a while, set - <c><anno>Number</anno></c> to a suitable value such as 10 or 20. - Thirdly, in embedded systems with limited amount of RAM - and no virtual memory, one might want to preserve memory - by setting <c><anno>Number</anno></c> to zero. (The value may be set - globally, see - <seealso marker="#system_flag/2">erlang:system_flag/2</seealso>.)</p> + <p>A few cases when it can be useful to change + <c>fullsweep_after</c>:</p> + <list type="bulleted"> + <item>If binaries that are no longer used are to be + thrown away as soon as possible. (Set + <c><anno>Number</anno></c> to zero.) + </item> + <item>A process that mostly have short-lived data is + fullsweeped seldom or never, that is, the old heap + contains mostly garbage. To ensure a fullsweep + occasionally, set <c><anno>Number</anno></c> to a + suitable value, such as 10 or 20. + </item> + <item>In embedded systems with a limited amount of RAM + and no virtual memory, you might want to preserve memory + by setting <c><anno>Number</anno></c> to zero. + (The value can be set globally, see + <seealso marker="#system_flag/2">erlang:system_flag/2</seealso>.) + </item> + </list> </item> <tag><c>{min_heap_size, <anno>Size</anno>}</c></tag> <item> - <p>This option is only useful for performance tuning. - In general, you should not use this option unless you - know that there is problem with execution times and/or - memory consumption, and you should measure to make sure - that the option improved matters. - </p> - <p>Gives a minimum heap size in words. Setting this value - higher than the system default might speed up some + <p>Useful only for performance tuning. Do not use this + option unless you know that there is problem with + execution times or memory consumption, and + ensure that the option improves matters.</p> + <p>Gives a minimum heap size, in words. Setting this value + higher than the system default can speed up some processes because less garbage collection is done. - Setting too high value, however, might waste memory and - slow down the system due to worse data locality. - Therefore, it is recommended to use this option only for + However, setting a too high value can waste memory and + slow down the system because of worse data locality. + Therefore, use this option only for fine-tuning an application and to measure the execution time with various <c><anno>Size</anno></c> values.</p> </item> <tag><c>{min_bin_vheap_size, <anno>VSize</anno>}</c></tag> <item> - <p>This option is only useful for performance tuning. - In general, you should not use this option unless you - know that there is problem with execution times and/or - memory consumption, and you should measure to make sure - that the option improved matters. - </p> - <p>Gives a minimum binary virtual heap size in words. Setting this value - higher than the system default might speed up some + <p>Useful only for performance tuning. Do not use this + option unless you know that there is problem with + execution times or memory consumption, and + ensure that the option improves matters.</p> + <p>Gives a minimum binary virtual heap size, in words. + Setting this value + higher than the system default can speed up some processes because less garbage collection is done. - Setting too high value, however, might waste memory. - Therefore, it is recommended to use this option only for + However, setting a too high value can waste memory. + Therefore, use this option only for fine-tuning an application and to measure the execution time with various <c><anno>VSize</anno></c> values.</p> </item> - </taglist> </desc> </func> + <func> <name name="spawn_opt" arity="5"/> - <type name="priority_level" /> - <fsummary>Create a new process with a function as entry point on a given node</fsummary> + <fsummary>Creates a new process with a function as entry point on a given node.</fsummary> + <type name="priority_level"/> <desc> - <p>Returns the pid of a new process started by the application - of <c><anno>Module</anno>:<anno>Function</anno></c> to <c><anno>Args</anno></c> on <c>Node</c>. If + <p>Returns the process identifier (pid) of a new process started + by the application + of <c><anno>Module</anno>:<anno>Function</anno></c> to + <c><anno>Args</anno></c> on <c><anno>Node</anno></c>. If <c><anno>Node</anno></c> does not exist, a useless pid is returned. Otherwise works like <seealso marker="#spawn_opt/4">spawn_opt/4</seealso>.</p> + <note><p>Option <c>monitor</c> is not supported by + <c>spawn_opt/5</c>.</p></note> </desc> </func> + <func> <name name="split_binary" arity="2"/> + <fsummary>Splits a binary into two.</fsummary> <type_desc variable="Pos">0..byte_size(Bin)</type_desc> - <fsummary>Split a binary into two</fsummary> <desc> - <p>Returns a tuple containing the binaries which are the result - of splitting <c><anno>Bin</anno></c> into two parts at position <c><anno>Pos</anno></c>. + <p>Returns a tuple containing the binaries that are the result + of splitting <c><anno>Bin</anno></c> into two parts at + position <c><anno>Pos</anno></c>. This is not a destructive operation. After the operation, - there will be three binaries altogether.</p> + there are three binaries altogether.</p> + <p>Example:</p> <pre> > <input>B = list_to_binary("0123456789").</input> <<"0123456789">> @@ -4741,156 +5604,269 @@ true</pre> 7</pre> </desc> </func> + <func> - <name name="start_timer" arity="3"/> - <type_desc variable="Time">0 <= Time <= 4294967295</type_desc> - <fsummary>Start a timer</fsummary> + <name name="start_timer" arity="4"/> + <fsummary>Starts a timer.</fsummary> <desc> - <p>Starts a timer which will send the message - <c>{timeout, <anno>TimerRef</anno>, <anno>Msg</anno>}</c> to <c><anno>Dest</anno></c> - after <c><anno>Time</anno></c> milliseconds.</p> - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c> it has to be a <c>pid()</c> of a local process, dead or alive.</p> - <p>The <c><anno>Time</anno></c> value can, in the current implementation, not be greater than 4294967295.</p> - <p>If <c><anno>Dest</anno></c> is an <c>atom()</c>, it is supposed to be the name of - a registered process. The process referred to by the name is - looked up at the time of delivery. No error is given if - the name does not refer to a process.</p> - <p>If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer will be automatically - canceled if the process referred to by the <c>pid()</c> is not alive, - or when the process exits. This feature was introduced in - erts version 5.4.11. Note that timers will not be - automatically canceled when <c><anno>Dest</anno></c> is an <c>atom()</c>.</p> + <p> + Starts a timer. When the timer expires, the message + <c>{timeout, <anno>TimerRef</anno>, <anno>Msg</anno>}</c> + is sent to the process identified by + <c><anno>Dest</anno></c>. + </p> + <p>Available <c><anno>Option</anno></c>s:</p> + <taglist> + <tag><c>{abs, false}</c></tag> + <item> + <p> + This is the default. It means the + <c><anno>Time</anno></c> value is interpreted + as a time in milli-seconds <em>relative</em> current + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso>. + </p> + </item> + <tag><c>{abs, true}</c></tag> + <item> + <p> + Absolute <c><anno>Time</anno></c> value. The + <c><anno>Time</anno></c> value is interpreted as an + absolute Erlang monotonic time in milli-seconds. + </p> + </item> + </taglist> + <p> + More <c><anno>Option</anno></c>s may be added in the future. + </p> + <p> + The absolute point in time, the timer is set to expire on, + has to be in the interval + <c>[</c><seealso marker="#system_info_start_time"><c>erlang:system_info(start_time)</c></seealso><c>, + </c><seealso marker="#system_info_end_time"><c>erlang:system_info(end_time)</c></seealso><c>]</c>. + Further, if a relative time is specified, the <c><anno>Time</anno></c> value + is not allowed to be negative. + </p> + <p> + If <c><anno>Dest</anno></c> is a <c>pid()</c>, it must + be a <c>pid()</c> of a process created on the current + runtime system instance. This process may or may not + have terminated. If <c><anno>Dest</anno></c> is an + <c>atom()</c>, it is interpreted as the name of a + locally registered process. The process referred to by the + name is looked up at the time of timer expiration. No error + is given if the name does not refer to a process. + </p> + <p> + If <c><anno>Dest</anno></c> is a <c>pid()</c>, the timer is + automatically canceled if the process referred to by the + <c>pid()</c> is not alive, or if the process exits. This + feature was introduced in ERTS version 5.4.11. Notice that + timers are not automatically canceled when + <c><anno>Dest</anno></c> is an <c>atom()</c>. + </p> <p>See also - <seealso marker="#send_after/3">erlang:send_after/3</seealso>, - <seealso marker="#cancel_timer/1">erlang:cancel_timer/1</seealso>, + <seealso marker="#send_after/4"><c>erlang:send_after/4</c></seealso>, + <seealso marker="#cancel_timer/2"><c>erlang:cancel_timer/2</c></seealso>, and - <seealso marker="#read_timer/1">erlang:read_timer/1</seealso>.</p> - <p>Failure: <c>badarg</c> if the arguments does not satisfy - the requirements specified above.</p> + <seealso marker="#read_timer/2"><c>erlang:read_timer/2</c></seealso>.</p> + <p>Failure: <c>badarg</c> if the arguments do not satisfy + the requirements specified here.</p> </desc> </func> + <func> - <name name="statistics" arity="1" clause_i="1"/> - <fsummary>Information about context switches</fsummary> + <name name="start_timer" arity="3"/> + <fsummary>Starts a timer.</fsummary> <desc> - <p><c><anno>ContextSwitches</anno></c> is the total number of context - switches since the system started.</p> + <p>Starts a timer. The same as calling + <seealso marker="#start_timer/4"><c>erlang:start_timer(<anno>Time</anno>, + <anno>Dest</anno>, <anno>Msg</anno>, [])</c></seealso>.</p> + </desc> + </func> + + <func> + <name name="statistics" arity="1" clause_i="1"/> + <fsummary>Information about active processes and ports.</fsummary> + <desc><marker id="statistics_active_tasks"></marker> + <p> + Returns a list where each element represents the amount + of active processes and ports on each run queue and its + associated scheduler. That is, the number of processes and + ports that are ready to run, or are currently running. The + element location in the list corresponds to the scheduler + and its run queue. The first element corresponds to scheduler + number 1 and so on. The information is <em>not</em> gathered + atomically. That is, the result is not necessarily a + consistent snapshot of the state, but instead quite + efficiently gathered. See also, + <seealso marker="#statistics_total_active_tasks"><c>statistics(total_active_tasks)</c></seealso>, + <seealso marker="#statistics_run_queue_lengths"><c>statistics(run_queue_lengths)</c></seealso>, and + <seealso marker="#statistics_total_run_queue_lengths"><c>statistics(total_run_queue_lengths)</c></seealso>. + </p> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="2"/> - <fsummary>Information about exact reductions</fsummary> + <fsummary>Information about context switches.</fsummary> <desc> - <marker id="statistics_exact_reductions"></marker> - <note><p><c>statistics(exact_reductions)</c> is - a more expensive operation than - <seealso marker="#statistics_reductions">statistics(reductions)</seealso> - especially on an Erlang machine with SMP support.</p> - </note> + <p>Returns the total number of context switches since the + system started.</p> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="3"/> - <fsummary>Information about garbage collection</fsummary> + <fsummary>Information about exact reductions.</fsummary> <desc> - <p>This information may not be valid for all implementations.</p> - <pre> -> <input>statistics(garbage_collection).</input> -{85,23961,0} -</pre> + <marker id="statistics_exact_reductions"></marker> + <p>Returns the number of exact reductions.</p> + <note><p><c>statistics(exact_reductions)</c> is + a more expensive operation than + <seealso marker="#statistics_reductions">statistics(reductions)</seealso>, + especially on an Erlang machine with SMP support.</p> + </note> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="4"/> - <fsummary>Information about io</fsummary> + <fsummary>Information about garbage collection.</fsummary> <desc> - <p><c><anno>Input</anno></c> is the total number of bytes received - through ports, and <c><anno>Output</anno></c> is the total number of - bytes output to ports.</p> + <p>Returns information about garbage collection, for example:</p> + <pre> +> <input>statistics(garbage_collection).</input> +{85,23961,0}</pre> + <p>This information can be invalid for some implementations.</p> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="5"/> - <fsummary>Information about reductions</fsummary> + <fsummary>Information about I/O.</fsummary> <desc> - <marker id="statistics_reductions"></marker> - <note> - <p>Since erts-5.5 (OTP release R11B) - this value does not include reductions performed in current - time slices of currently scheduled processes. If an - exact value is wanted, use - <seealso marker="#statistics_exact_reductions">statistics(exact_reductions)</seealso>.</p> - </note> - <pre> -> <input>statistics(reductions).</input> -{2046,11} -</pre> + <p>Returns <c><anno>Input</anno></c>, + which is the total number of bytes + received through ports, and <c><anno>Output</anno></c>, + which is the total number of bytes output to ports.</p> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="6"/> - <fsummary>Information about the run-queue</fsummary> + <fsummary>Information about reductions.</fsummary> <desc> - <p>Returns the total length of the run queues, that is, the number - of processes that are ready to run on all available run queues.</p> + <marker id="statistics_reductions"></marker> + <p>Returns information about reductions, for example:</p> + <pre> +> <input>statistics(reductions).</input> +{2046,11}</pre> + <note><p>As from <c>ERTS</c> 5.5 (OTP R11B), + this value does not include reductions performed in current + time slices of currently scheduled processes. If an + exact value is wanted, use + <seealso marker="#statistics_exact_reductions">statistics(exact_reductions)</seealso>.</p> + </note> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="7"/> - <fsummary>Information about run-time</fsummary> - <desc> - <p>Note that the run-time is the sum of the run-time for all - threads in the Erlang run-time system and may therefore be greater - than the wall-clock time.</p> - <pre> -> <input>statistics(runtime).</input> -{1690,1620} -</pre> + <fsummary>Information about the run-queues.</fsummary> + <desc><marker id="statistics_run_queue"></marker> + <p> + Returns the total length of the run-queues. That is, the number + of processes and ports that are ready to run on all available + run-queues. The information is gathered atomically. That + is, the result is a consistent snapshot of the state, but + this operation is much more expensive compared to + <seealso marker="#statistics_total_run_queue_lengths"><c>statistics(total_run_queue_lengths)</c></seealso>. + This especially when a large amount of schedulers is used. + </p> </desc> </func> + <func> <name name="statistics" arity="1" clause_i="8"/> - <fsummary>Information about each schedulers work time</fsummary> - <desc> - <marker id="statistics_scheduler_wall_time"></marker> - <p> - Returns a list of tuples with <c>{<anno>SchedulerId</anno>, - <anno>ActiveTime</anno>, <anno>TotalTime</anno>}</c>, where - <c>SchedulerId</c> is an integer id of the scheduler, <c>ActiveTime</c> is - the duration the scheduler has been busy, <c>TotalTime</c> is the total time duration since - <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso> - activation. The time unit is not defined and may be subject to change - between releases, operating systems and system restarts. - <c>scheduler_wall_time</c> should only be used to calculate relative - values for scheduler-utilization. <c>ActiveTime</c> can never exceed <c>TotalTime</c>. - </p> - - <p>The definition of a busy scheduler is when it is not idle or not - scheduling (selecting) a process or port, meaning; executing process - code, executing linked-in-driver or NIF code, executing - built-in-functions or any other runtime handling, garbage collecting - or handling any other memory management. Note, a scheduler may also be - busy even if the operating system has scheduled out the scheduler - thread. - </p> + <fsummary>Information about the run-queue lengths.</fsummary> + <desc><marker id="statistics_run_queue_lengths"></marker> + <p> + Returns a list where each element represents the amount + of processes and ports ready to run for each run queue. The + element location in the list corresponds to the run queue + of a scheduler. The first element corresponds to the run + queue of scheduler number 1 and so on. The information is + <em>not</em> gathered atomically. That is, the result is + not necessarily a consistent snapshot of the state, but + instead quite efficiently gathered. See also, + <seealso marker="#statistics_total_run_queue_lengths"><c>statistics(total_run_queue_lengths)</c></seealso>, + <seealso marker="#statistics_active_tasks"><c>statistics(active_tasks)</c></seealso>, and + <seealso marker="#statistics_total_active_tasks"><c>statistics(total_active_tasks)</c></seealso>. + </p> + </desc> + </func> - <p> - Returns <c>undefined</c> if the system flag - <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso> - is turned off. - </p> + <func> + <name name="statistics" arity="1" clause_i="9"/> + <fsummary>Information about runtime.</fsummary> + <desc> + <p>Returns information about runtime, in milliseconds.</p> + <p>This is the sum of the runtime for all threads + in the Erlang runtime system and can therefore be greater + than the wall clock time.</p> + <p>Example:</p> + <pre> +> <input>statistics(runtime).</input> +{1690,1620}</pre> + </desc> + </func> - <p>The list of scheduler information is unsorted and may appear in different order - between calls. - </p> - <p>Using <c>scheduler_wall_time</c> to calculate scheduler utilization.</p> + <func> + <name name="statistics" arity="1" clause_i="10"/> + <fsummary>Information about each schedulers work time.</fsummary> + <desc> + <marker id="statistics_scheduler_wall_time"></marker> + <p>Returns a list of tuples with + <c>{<anno>SchedulerId</anno>, <anno>ActiveTime</anno>, + <anno>TotalTime</anno>}</c>, where + <c><anno>SchedulerId</anno></c> is an integer ID of the scheduler, + <c><anno>ActiveTime</anno></c> is + the duration the scheduler has been busy, and + <c><anno>TotalTime</anno></c> is the total time duration since + <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso> + activation. The time unit is undefined and can be subject + to change between releases, OSs, and system restarts. + <c>scheduler_wall_time</c> is only to be used to + calculate relative values for scheduler-utilization. + <c><anno>ActiveTime</anno></c> can never exceed + <c><anno>TotalTime</anno></c>.</p> + <p>The definition of a busy scheduler is when it is not idle + and is not scheduling (selecting) a process or port, + that is:</p> + <list type="bulleted"> + <item>Executing process code</item> + <item>Executing linked-in-driver or NIF code</item> + <item>Executing built-in-functions, or any other runtime + handling</item> + <item>Garbage collecting</item> + <item>Handling any other memory management</item> + </list> + <p>Notice that a scheduler can also be busy even if the + OS has scheduled out the scheduler thread.</p> + <p>Returns <c>undefined</c> if system flag + <seealso marker="#system_flag_scheduler_wall_time">scheduler_wall_time</seealso> + is turned off.</p> + <p>The list of scheduler information is unsorted and can + appear in different order between calls.</p> + <p>Using <c>scheduler_wall_time</c> to calculate scheduler-utilization:</p> <pre> > <input>erlang:system_flag(scheduler_wall_time, true).</input> false > <input>Ts0 = lists:sort(erlang:statistics(scheduler_wall_time)), ok.</input> -ok -</pre> - <p>Some time later we will take another snapshot and calculate scheduler-utilization per scheduler.</p> +ok</pre> + <p>Some time later the user takes another snapshot and calculates + scheduler-utilization per scheduler, for example:</p> <pre> > <input>Ts1 = lists:sort(erlang:statistics(scheduler_wall_time)), ok.</input> ok @@ -4903,86 +5879,127 @@ ok {5,0.9717956667018103}, {6,0.9739235846420741}, {7,0.973237033077876}, - {8,0.9741297293248656}] -</pre> - <p>Using the same snapshots to calculate a total scheduler-utilization.</p> + {8,0.9741297293248656}]</pre> + <p>Using the same snapshots to calculate a total scheduler-utilization:</p> <pre> > <input>{A, T} = lists:foldl(fun({{_, A0, T0}, {_, A1, T1}}, {Ai,Ti}) -> {Ai + (A1 - A0), Ti + (T1 - T0)} end, {0, 0}, lists:zip(Ts0,Ts1)), A/T.</input> -0.9769136803764825 -</pre> +0.9769136803764825</pre> <note> - <p><c>scheduler_wall_time</c> is by default disabled. Use <c>erlang:system_flag(scheduler_wall_time, true)</c> to enable it. </p> + <p><c>scheduler_wall_time</c> is by default disabled. To + enable it, use + <c>erlang:system_flag(scheduler_wall_time, true)</c>.</p> </note> </desc> </func> + + <func> + <name name="statistics" arity="1" clause_i="11"/> + <fsummary>Information about active processes and ports.</fsummary> + <desc><marker id="statistics_total_active_tasks"></marker> + <p> + Returns the total amount of active processes and ports in + the system. That is, the number of processes and ports that + are ready to run, or are currently running. The information + is <em>not</em> gathered atomically. That is, the result + is not necessarily a consistent snapshot of the state, but + instead quite efficiently gathered. See also, + <seealso marker="#statistics_active_tasks"><c>statistics(active_tasks)</c></seealso>, + <seealso marker="#statistics_run_queue_lengths"><c>statistics(run_queue_lengths)</c></seealso>, and + <seealso marker="#statistics_total_run_queue_lengths"><c>statistics(total_run_queue_lengths)</c></seealso>. + </p> + </desc> + </func> + <func> - <name name="statistics" arity="1" clause_i="9"/> - <fsummary>Information about wall-clock</fsummary> + <name name="statistics" arity="1" clause_i="12"/> + <fsummary>Information about the run-queue lengths.</fsummary> + <desc><marker id="statistics_total_run_queue_lengths"></marker> + <p> + Returns the total length of the run-queues. That is, the number + of processes and ports that are ready to run on all available + run-queues. The information is <em>not</em> gathered atomically. + That is, the result is not necessarily a consistent snapshot of + the state, but much more efficiently gathered compared to + <seealso marker="#statistics_run_queue"><c>statistics(run_queue)</c></seealso>. + See also, + <seealso marker="#statistics_run_queue_lengths"><c>statistics(run_queue_lengths)</c></seealso>, + <seealso marker="#statistics_total_active_tasks"><c>statistics(total_active_tasks)</c></seealso>, and + <seealso marker="#statistics_active_tasks"><c>statistics(active_tasks)</c></seealso>. + </p> + </desc> + </func> + + <func> + <name name="statistics" arity="1" clause_i="13"/> + <fsummary>Information about wall clock.</fsummary> <desc> - <p><c>wall_clock</c> can be used in the same manner as + <p>Returns information about wall clock. <c>wall_clock</c> can + be used in the same manner as <c>runtime</c>, except that real time is measured as opposed to runtime or CPU time.</p> </desc> </func> + <func> <name name="suspend_process" arity="2"/> - <fsummary>Suspend a process</fsummary> + <fsummary>Suspends a process.</fsummary> <desc> <p>Increases the suspend count on the process identified by - <c><anno>Suspendee</anno></c> and puts it in the suspended state if it isn't - already in the suspended state. A suspended process will not be - scheduled for execution until the process has been resumed. - </p> - + <c><anno>Suspendee</anno></c> and puts it in the suspended + state if it is not + already in that state. A suspended process will not be + scheduled for execution until the process has been resumed.</p> <p>A process can be suspended by multiple processes and can be suspended multiple times by a single process. A suspended - process will not leave the suspended state until its suspend - count reach zero. The suspend count of <c><anno>Suspendee</anno></c> - is decreased when + process does not leave the suspended state until its suspend + count reaches zero. The suspend count of + <c><anno>Suspendee</anno></c> is decreased when <seealso marker="#resume_process/1">erlang:resume_process(<anno>Suspendee</anno>)</seealso> is called by the same process that called - <c>erlang:suspend_process(<anno>Suspendee</anno>)</c>. All increased suspend - counts on other processes acquired by a process will automatically be + <c>erlang:suspend_process(<anno>Suspendee</anno>)</c>. + All increased suspend + counts on other processes acquired by a process are automatically decreased when the process terminates.</p> - - <p>Currently the following options (<c><anno>Opt</anno></c>s) are available:</p> + <p>The options (<c><anno>Opt</anno></c>s) are as follows:</p> <taglist> <tag><c>asynchronous</c></tag> <item> A suspend request is sent to the process identified by - <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c> will eventually suspend - unless it is resumed before it was able to suspend. The caller - of <c>erlang:suspend_process/2</c> will return immediately, - regardless of whether the <c><anno>Suspendee</anno></c> has suspended yet - or not. Note that the point in time when the <c><anno>Suspendee</anno></c> - will actually suspend cannot be deduced from other events - in the system. The only guarantee given is that the - <c><anno>Suspendee</anno></c> will <em>eventually</em> suspend (unless it - is resumed). If the <c>asynchronous</c> option has <em>not</em> - been passed, the caller of <c>erlang:suspend_process/2</c> will - be blocked until the <c><anno>Suspendee</anno></c> has actually suspended. + <c><anno>Suspendee</anno></c>. <c><anno>Suspendee</anno></c> + eventually suspends + unless it is resumed before it could suspend. The caller + of <c>erlang:suspend_process/2</c> returns immediately, + regardless of whether <c><anno>Suspendee</anno></c> has + suspended yet or not. The point in time when + <c><anno>Suspendee</anno></c> suspends cannot be deduced + from other events in the system. It is only guaranteed that + <c><anno>Suspendee</anno></c> <em>eventually</em> suspends + (unless it + is resumed). If option <c>asynchronous</c> has <em>not</em> + been passed, the caller of <c>erlang:suspend_process/2</c> is + blocked until <c><anno>Suspendee</anno></c> has suspended. </item> <tag><c>unless_suspending</c></tag> <item> - The process identified by <c><anno>Suspendee</anno></c> will be suspended - unless the calling process already is suspending the - <c><anno>Suspendee</anno></c>. If <c>unless_suspending</c> is combined - with the <c>asynchronous</c> option, a suspend request will be - sent unless the calling process already is suspending the - <c><anno>Suspendee</anno></c> or if a suspend request already has been sent - and is in transit. If the calling process already is suspending - the <c><anno>Suspendee</anno></c>, or if combined with the <c>asynchronous</c> - option and a send request already is in transit, - <c>false</c> is returned and the suspend count on <c><anno>Suspendee</anno></c> - will remain unchanged. + The process identified by <c><anno>Suspendee</anno></c> is + suspended unless the calling process already is suspending + <c><anno>Suspendee</anno></c>. + If <c>unless_suspending</c> is combined + with option <c>asynchronous</c>, a suspend request is + sent unless the calling process already is suspending + <c><anno>Suspendee</anno></c> or if a suspend request + already has been sent and is in transit. If the calling + process already is suspending <c><anno>Suspendee</anno></c>, + or if combined with option <c>asynchronous</c> + and a send request already is in transit, + <c>false</c> is returned and the suspend count on + <c><anno>Suspendee</anno></c> remains unchanged. </item> </taglist> - <p>If the suspend count on the process identified by - <c><anno>Suspendee</anno></c> was increased, <c>true</c> is returned; otherwise, - <c>false</c> is returned.</p> - + <c><anno>Suspendee</anno></c> is increased, <c>true</c> + is returned, otherwise <c>false</c>.</p> <warning> <p>This BIF is intended for debugging only.</p> </warning> @@ -4990,282 +6007,322 @@ ok <taglist> <tag><c>badarg</c></tag> <item> - If <c><anno>Suspendee</anno></c> isn't a process identifier. + If <c><anno>Suspendee</anno></c> is not a process identifier. </item> <tag><c>badarg</c></tag> <item> - If the process identified by <c><anno>Suspendee</anno></c> is same the process as - the process calling <c>erlang:suspend_process/2</c>. + If the process identified by <c><anno>Suspendee</anno></c> + is the same process + as the process calling <c>erlang:suspend_process/2</c>. </item> <tag><c>badarg</c></tag> <item> - If the process identified by <c><anno>Suspendee</anno></c> is not alive. + If the process identified by <c><anno>Suspendee</anno></c> + is not alive. </item> <tag><c>badarg</c></tag> <item> - If the process identified by <c><anno>Suspendee</anno></c> resides on another node. + If the process identified by <c><anno>Suspendee</anno></c> + resides on another node. </item> <tag><c>badarg</c></tag> <item> - If <c><anno>OptList</anno></c> isn't a proper list of valid <c><anno>Opt</anno></c>s. + If <c><anno>OptList</anno></c> is not a proper list of valid + <c><anno>Opt</anno></c>s. </item> <tag><c>system_limit</c></tag> <item> - If the process identified by <c><anno>Suspendee</anno></c> has been suspended more - times by the calling process than can be represented by the - currently used internal data structures. The current system limit - is larger than 2 000 000 000 suspends, and it will never be less - than that. + If the process identified by <c><anno>Suspendee</anno></c> + has been suspended + more times by the calling process than can be represented by the + currently used internal data structures. The system limit is + higher than 2,000,000,000 suspends and will never be lower. </item> </taglist> </desc> </func> + <func> <name name="suspend_process" arity="1"/> - <fsummary>Suspend a process</fsummary> + <fsummary>Suspends a process.</fsummary> <desc> - <p>Suspends the process identified by <c><anno>Suspendee</anno></c>. The - same as calling - <seealso marker="#suspend_process/2">erlang:suspend_process(<anno>Suspendee</anno>, [])</seealso>. For more information see the documentation of <seealso marker="#suspend_process/2">erlang:suspend_process/2</seealso>. - </p> + <p>Suspends the process identified by + <c><anno>Suspendee</anno></c>. The same as calling + <seealso marker="#suspend_process/2">erlang:suspend_process(<anno>Suspendee</anno>, + [])</seealso>.</p> <warning> <p>This BIF is intended for debugging only.</p> </warning> </desc> </func> + <func> <name name="system_flag" arity="2" clause_i="1"/> - <fsummary>Set system flag backtrace_depth</fsummary> + <fsummary>Sets system flag <c>backtrace_depth</c>.</fsummary> <desc> <p>Sets the maximum depth of call stack back-traces in the exit reason element of <c>'EXIT'</c> tuples.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> <name name="system_flag" arity="2" clause_i="2"/> + <fsummary>Sets system flag <c>cpu_topology</c>.</fsummary> <type name="cpu_topology"/> <type name="level_entry"/> <type name="level_tag"/> <type name="sub_level"/> <type name="info_list"/> - <fsummary>Set system flag cpu_topology</fsummary> <desc> <warning> <p><marker id="system_flag_cpu_topology"></marker> - This argument is <em>deprecated</em> and - scheduled for removal in erts-5.10/OTP-R16. Instead of using - this argument you are advised to use the <c>erl</c> command - line argument <seealso marker="erts:erl#+sct">+sct</seealso>. - When this argument has been removed a final CPU topology to use - will be determined at emulator boot time.</p> + This argument is <em>deprecated</em> and scheduled for + removal in <c>ERTS</c> 5.10/OTP R16. Instead of using this + argument, use command-line argument + <seealso marker="erts:erl#+sct">+sct</seealso> in + <c>erl(1)</c>.</p> + <p>When this argument is removed, a final CPU topology + to use is determined at emulator boot time.</p> </warning> - <p>Sets the user defined <c><anno>CpuTopology</anno></c>. The user defined - CPU topology will override any automatically detected - CPU topology. By passing <c>undefined</c> as <c><anno>CpuTopology</anno></c> - the system will revert back to the CPU topology automatically + <p>Sets the user-defined <c><anno>CpuTopology</anno></c>. + The user-defined + CPU topology overrides any automatically detected + CPU topology. By passing <c>undefined</c> as + <c><anno>CpuTopology</anno></c>, + the system reverts to the CPU topology automatically detected. The returned value equals the value returned from <c>erlang:system_info(cpu_topology)</c> before the - change was made. - </p> + change was made.</p> <p>Returns the old value of the flag.</p> <p>The CPU topology is used when binding schedulers to logical processors. If schedulers are already bound when the CPU - topology is changed, the schedulers will be sent a request - to rebind according to the new CPU topology. - </p> - <p>The user defined CPU topology can also be set by passing - the <seealso marker="erts:erl#+sct">+sct</seealso> command - line argument to <c>erl</c>. - </p> - <p>For information on the <c><anno>CpuTopology</anno></c> type - and more, see the documentation of - <seealso marker="#system_info_cpu_topology">erlang:system_info(cpu_topology)</seealso>, - and the <c>erl</c> <seealso marker="erts:erl#+sct">+sct</seealso> - and <seealso marker="erts:erl#+sbt">+sbt</seealso> - command line flags. - </p> + topology is changed, the schedulers are sent a request + to rebind according to the new CPU topology.</p> + <p>The user-defined CPU topology can also be set by passing + command-line argument + <seealso marker="erts:erl#+sct">+sct</seealso> to + <c>erl(1)</c>.</p> + <p>For information on type <c><anno>CpuTopology</anno></c> + and more, see + <seealso marker="#system_info_cpu_topology">erlang:system_info(cpu_topology)</seealso> + as well as the command-line flags + <seealso marker="erts:erl#+sct">+sct</seealso> and + <seealso marker="erts:erl#+sbt">+sbt</seealso> in + <c>erl(1)</c>.</p> </desc> </func> + <func> <name name="system_flag" arity="2" clause_i="3"/> - <fsummary>Set system flag fullsweep_after</fsummary> + <fsummary>Sets <c>system_flag_dirty_cpu_schedulers_online</c>.</fsummary> + <desc> + <p><marker id="system_flag_dirty_cpu_schedulers_online"></marker> + Sets the number of dirty CPU schedulers online. Range is + <![CDATA[1 <= DirtyCPUSchedulersOnline <= N]]>, where <c>N</c> + is the smallest of the return values of + <c>erlang:system_info(dirty_cpu_schedulers)</c> and + <c>erlang:system_info(schedulers_online)</c>.</p> + <p>Returns the old value of the flag.</p> + <p>The number of dirty CPU schedulers online can change if the + number of schedulers online changes. For example, if 12 + schedulers and 6 dirty CPU schedulers are online, and + <c>system_flag/2</c> is used to set the number of + schedulers online to 6, then the number of dirty CPU + schedulers online is automatically decreased by half as well, + down to 3. Similarly, the number of dirty CPU schedulers + online increases proportionally to increases in the number of + schedulers online.</p> + <note><p>The dirty schedulers functionality is experimental. + Enable support for dirty schedulers when building OTP to + try out the functionality.</p> + </note> + <p>For more information, see + <seealso marker="#system_info_dirty_cpu_schedulers">erlang:system_info(dirty_cpu_schedulers)</seealso> + and + <seealso marker="#system_info_dirty_cpu_schedulers_online">erlang:system_info(dirty_cpu_schedulers_online)</seealso>.</p> + </desc> + </func> + + <func> + <name name="system_flag" arity="2" clause_i="4"/> + <fsummary>Sets system flag <c>fullsweep_after</c>.</fsummary> <desc> - <p><c><anno>Number</anno></c> is a non-negative integer which indicates + <p>Sets system flag <c>fullsweep_after</c>. + <c><anno>Number</anno></c> is a non-negative integer indicating how many times generational garbage collections can be done without forcing a fullsweep collection. The value - applies to new processes; processes already running are + applies to new processes, while processes already running are not affected.</p> <p>Returns the old value of the flag.</p> <p>In low-memory systems (especially without virtual - memory), setting the value to 0 can help to conserve + memory), setting the value to <c>0</c> can help to conserve memory.</p> - <p>An alternative way to set this value is through the - (operating system) environment variable - <c>ERL_FULLSWEEP_AFTER</c>.</p> + <p>This value can also be set through (OS) + environment variable <c>ERL_FULLSWEEP_AFTER</c>.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="4"/> - <fsummary>Set system flag min_heap_size</fsummary> - <desc> - <p>Sets the default minimum heap size for processes. The - size is given in words. The new <c>min_heap_size</c> only - effects processes spawned after the change of - <c>min_heap_size</c> has been made. - The <c>min_heap_size</c> can be set for individual - processes by use of + <name name="system_flag" arity="2" clause_i="5"/> + <fsummary>Sets system flag <c>min_heap_size</c>.</fsummary> + <desc> + <p>Sets the default minimum heap size for processes. The size + is given in words. The new <c>min_heap_size</c> effects + only processes spawned after the change of + <c>min_heap_size</c> has been made. <c>min_heap_size</c> + can be set for individual processes by using <seealso marker="#spawn_opt/4">spawn_opt/N</seealso> or - <seealso marker="#process_flag/2">process_flag/2</seealso>. </p> + <seealso marker="#process_flag/2">process_flag/2</seealso>.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="5"/> - <fsummary>Set system flag min_bin_vheap_size</fsummary> + <name name="system_flag" arity="2" clause_i="6"/> + <fsummary>Sets system flag <c>min_bin_vheap_size</c>.</fsummary> <desc> - <p>Sets the default minimum binary virtual heap size for processes. The - size is given in words. The new <c>min_bin_vhheap_size</c> only - effects processes spawned after the change of + <p>Sets the default minimum binary virtual heap size for + processes. The size is given in words. + The new <c>min_bin_vhheap_size</c> effects only + processes spawned after the change of <c>min_bin_vhheap_size</c> has been made. - The <c>min_bin_vheap_size</c> can be set for individual - processes by use of + <c>min_bin_vheap_size</c> can be set for individual + processes by using <seealso marker="#spawn_opt/4">spawn_opt/N</seealso> or - <seealso marker="#process_flag/2">process_flag/2</seealso>. </p> + <seealso marker="#process_flag/2">process_flag/2</seealso>.</p> <p>Returns the old value of the flag.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="6"/> - <fsummary>Set system flag multi_scheduling</fsummary> + <name name="system_flag" arity="2" clause_i="7"/> + <fsummary>Sets system flag <c>multi_scheduling</c>.</fsummary> <desc> <p><marker id="system_flag_multi_scheduling"></marker> If multi-scheduling is enabled, more than one scheduler thread is used by the emulator. Multi-scheduling can be - blocked. When multi-scheduling has been blocked, only - one scheduler thread will schedule Erlang processes.</p> - <p>If <c><anno>BlockState</anno> =:= block</c>, multi-scheduling will - be blocked. If <c><anno>BlockState</anno> =:= unblock</c> and no-one - else is blocking multi-scheduling and this process has - only blocked one time, multi-scheduling will be unblocked. - One process can block multi-scheduling multiple times. - If a process has blocked multiple times, it has to + blocked. When multi-scheduling is blocked, only + one scheduler thread schedules Erlang processes.</p> + <p>If <c><anno>BlockState</anno> =:= block</c>, multi-scheduling is + blocked. If <c><anno>BlockState</anno> =:= unblock</c> and no one + else blocks multi-scheduling, and this process has + blocked only once, multi-scheduling is unblocked.</p> + <p>One process can block multi-scheduling multiple times. + If a process has blocked multiple times, it must unblock exactly as many times as it has blocked before it has released its multi-scheduling block. If a process that - has blocked multi-scheduling exits, it will release its + has blocked multi-scheduling exits, it releases its blocking of multi-scheduling.</p> <p>The return values are <c>disabled</c>, <c>blocked</c>, or <c>enabled</c>. The returned value describes the state just after the call to <c>erlang:system_flag(multi_scheduling, <anno>BlockState</anno>)</c> - has been made. The return values are described in the - documentation of <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>.</p> - <p><em>NOTE</em>: Blocking of multi-scheduling should normally - not be needed. If you feel that you need to - block multi-scheduling, think through the - problem at least a couple of times again. - Blocking multi-scheduling should only be used - as a last resort since it will most likely be - a <em>very inefficient</em> way to solve the - problem.</p> - <p>See also <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, + has been made. For information about the return values, see + <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>.</p> + <note><p>Blocking of multi-scheduling is normally not needed. + If you feel that you need to block multi-scheduling, + consider it a few more times again. Blocking multi-scheduling + is only to be used as a last resort, as it is most likely + a <em>very inefficient</em> way to solve the problem.</p> + </note> + <p>See also + <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>, and <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="7"/> + <name name="system_flag" arity="2" clause_i="8"/> + <fsummary>Sets system flag <c>scheduler_bind_type</c>.</fsummary> <type name="scheduler_bind_type"/> - <fsummary>Set system flag scheduler_bind_type</fsummary> <desc> <warning> <p><marker id="system_flag_scheduler_bind_type"></marker> - This argument is <em>deprecated</em> and - scheduled for removal in erts-5.10/OTP-R16. Instead of using - this argument you are advised to use the <c>erl</c> command - line argument <seealso marker="erts:erl#+sbt">+sbt</seealso>. - When this argument has been removed a final scheduler bind type - to use will be determined at emulator boot time.</p> + This argument is <em>deprecated</em> and scheduled for + removal in <c>ERTS</c> 5.10/OTP R16. Instead of using this + argument, use command-line argument + <seealso marker="erts:erl#+sbt">+sbt</seealso> in <c>erl(1)</c>. + When this argument is removed, a final scheduler bind + type to use is determined at emulator boot time.</p> </warning> <p>Controls if and how schedulers are bound to logical processors.</p> - <p>When <c>erlang:system_flag(scheduler_bind_type, <anno>How</anno>)</c> is - called, an asynchronous signal is sent to all schedulers - online which causes them to try to bind or unbind as requested. - <em>NOTE:</em> If a scheduler fails to bind, this - will often be silently ignored. This since it isn't always - possible to verify valid logical processor identifiers. If - an error is reported, it will be reported to the - <c>error_logger</c>. If you want to verify that the - schedulers actually have bound as requested, call - <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>. - </p> - <p>Schedulers can currently only be bound on newer Linux, + <p>When <c>erlang:system_flag(scheduler_bind_type, <anno>How</anno>)</c> + is called, an asynchronous signal is sent to all schedulers + online, causing them to try to bind or unbind as requested.</p> + <note><p>If a scheduler fails to bind, this is often silently + ignored, as it is not always possible to verify valid + logical processor identifiers. If an error is reported, + it is reported to <c>error_logger</c>. To verify that the + schedulers have bound as requested, call + <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.</p> + </note> + <p>Schedulers can be bound on newer Linux, Solaris, FreeBSD, and Windows systems, but more systems will be - supported in the future. - </p> + supported in future releases.</p> <p>In order for the runtime system to be able to bind schedulers, - the CPU topology needs to be known. If the runtime system fails - to automatically detect the CPU topology, it can be defined. + the CPU topology must be known. If the runtime system fails + to detect the CPU topology automatically, it can be defined. For more information on how to define the CPU topology, see - the <c>erl</c> <seealso marker="erts:erl#+sct">+sct</seealso> command - line flag. - </p> - <p>The runtime system will by default <em>not</em> bind schedulers - to logical processors. - </p> - <p><em>NOTE:</em> If the Erlang runtime system is the only - operating system process that binds threads to logical processors, - this improves the performance of the runtime system. However, - if other operating system processes (as for example another Erlang - runtime system) also bind threads to logical processors, there - might be a performance penalty instead. In some cases this - performance penalty might be severe. If this is the case, you - are advised to not bind the schedulers.</p> - <p>Schedulers can be bound in different ways. The <c><anno>How</anno></c> - argument determines how schedulers are bound. <c><anno>How</anno></c> can - currently be one of:</p> + command-line flag <seealso marker="erts:erl#+sct">+sct</seealso> + in <c>erl(1)</c>.</p> + <p>The runtime system does by default <em>not</em> bind schedulers + to logical processors.</p> + <note><p>If the Erlang runtime system is the only OS + process binding threads to logical processors, this + improves the performance of the runtime system. However, + if other OS processes (for example, another Erlang + runtime system) also bind threads to logical processors, + there can be a performance penalty instead. Sometimes this + performance penalty can be severe. If so, it is recommended + to not bind the schedulers.</p> + </note> + <p>Schedulers can be bound in different ways. Argument + <c><anno>How</anno></c> determines how schedulers are + bound and can be any of the following:</p> <taglist> <tag><c>unbound</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt u</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt u</seealso> in <c>erl(1)</c>. </p></item> <tag><c>no_spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt ns</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt ns</seealso> in <c>erl(1)</c>. </p></item> <tag><c>thread_spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt ts</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt ts</seealso> in <c>erl(1)</c>. </p></item> <tag><c>processor_spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt ps</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt ps</seealso> in <c>erl(1)</c>. </p></item> <tag><c>spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt s</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt s</seealso> in <c>erl(1)</c>. </p></item> <tag><c>no_node_thread_spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt nnts</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt nnts</seealso> in <c>erl(1)</c>. </p></item> <tag><c>no_node_processor_spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt nnps</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt nnps</seealso> in <c>erl(1)</c>. </p></item> <tag><c>thread_no_node_processor_spread</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt tnnps</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt tnnps</seealso> in <c>erl(1)</c>. </p></item> <tag><c>default_bind</c></tag> - <item><p>Same as the <c>erl</c> command line argument - <seealso marker="erts:erl#+sbt">+sbt db</seealso>. + <item><p>Same as command-line argument + <seealso marker="erts:erl#+sbt">+sbt db</seealso> in <c>erl(1)</c>. </p></item> </taglist> - <p>The value returned equals <c><anno>How</anno></c> before the - <c>scheduler_bind_type</c> flag was changed.</p> - <p>Failure:</p> + <p>The returned value equals <c><anno>How</anno></c> before flag + <c>scheduler_bind_type</c> was changed.</p> + <p>Failures:</p> <taglist> <tag><c>notsup</c></tag> <item> @@ -5273,130 +6330,171 @@ ok </item> <tag><c>badarg</c></tag> <item> - <p>If <c>How</c> isn't one of the documented alternatives.</p> + <p>If <c><anno>How</anno></c> is not one of the documented + alternatives.</p> </item> <tag><c>badarg</c></tag> <item> - <p>If no CPU topology information is available.</p> + <p>If CPU topology information is unavailable.</p> </item> </taglist> <p>The scheduler bind type can also be set by passing - the <seealso marker="erts:erl#+sbt">+sbt</seealso> command - line argument to <c>erl</c>. - </p> + command-line argument + <seealso marker="erts:erl#+sbt">+sbt</seealso> to <c>erl(1)</c>.</p> <p>For more information, see <seealso marker="#system_info_scheduler_bind_type">erlang:system_info(scheduler_bind_type)</seealso>, <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>, - the <c>erl</c> <seealso marker="erts:erl#+sbt">+sbt</seealso> - and <seealso marker="erts:erl#+sct">+sct</seealso> command line - flags. - </p> + as well as command-line flags + <seealso marker="erts:erl#+sbt">+sbt</seealso> + and <seealso marker="erts:erl#+sct">+sct</seealso> + in <c>erl(1)</c>.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="8"/> - <fsummary>Set system flag scheduler_wall_time</fsummary> + <name name="system_flag" arity="2" clause_i="9"/> + <fsummary>Sets system flag <c>scheduler_wall_time</c>.</fsummary> <desc><p><marker id="system_flag_scheduler_wall_time"></marker> - Turns on/off scheduler wall time measurements. </p> - <p>For more information see, - <seealso marker="#statistics_scheduler_wall_time">erlang:statistics(scheduler_wall_time)</seealso>. - </p> + Turns on or off scheduler wall time measurements.</p> + <p>For more information, see + <seealso marker="#statistics_scheduler_wall_time">erlang:statistics(scheduler_wall_time)</seealso>.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="9"/> - <fsummary>Set system flag schedulers_online</fsummary> + <name name="system_flag" arity="2" clause_i="10"/> + <fsummary>Sets system flag <c>schedulers_online</c>.</fsummary> <desc> <p><marker id="system_flag_schedulers_online"></marker> - Sets the amount of schedulers online. Valid range is - <![CDATA[1 <= SchedulersOnline <= erlang:system_info(schedulers)]]>. - </p> + Sets the number of schedulers online. Range is + <![CDATA[1 <= SchedulersOnline <= erlang:system_info(schedulers)]]>.</p> <p>Returns the old value of the flag.</p> - <p>For more information see, - <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>, + <p>If the emulator was built with support for + <seealso marker="#system_flag_dirty_cpu_schedulers_online">dirty schedulers</seealso>, + changing the number of schedulers online can also change the + number of dirty CPU schedulers online. For example, if 12 + schedulers and 6 dirty CPU schedulers are online, and + <c>system_flag/2</c> is used to set the number of schedulers + online to 6, then the number of dirty CPU schedulers online + is automatically decreased by half as well, down to 3. + Similarly, the number of dirty CPU schedulers online increases + proportionally to increases in the number of schedulers online.</p> + <p>For more information, see + <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso> and - <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>. - </p> + <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>.</p> </desc> </func> + <func> - <name name="system_flag" arity="2" clause_i="10"/> - <fsummary>Set system flag trace_control_word</fsummary> + <name name="system_flag" arity="2" clause_i="11"/> + <fsummary>Sets system flag <c>trace_control_word</c>.</fsummary> <desc> - <p>Sets the value of the node's trace control word to - <c><anno>TCW</anno></c>. <c><anno>TCW</anno></c> should be an unsigned integer. For - more information see documentation of the + <p>Sets the value of the node trace control word to + <c><anno>TCW</anno></c>, which is to be an unsigned integer. + For more information, see the function <seealso marker="erts:match_spec#set_tcw">set_tcw</seealso> - function in the match specification documentation in the - ERTS User's Guide.</p> + in Section "Match Specifications in Erlang" in the + User's Guide.</p> <p>Returns the old value of the flag.</p> </desc> </func> + + <func> + <name name="system_flag" arity="2" clause_i="12"/> + <fsummary>Finalize the Time Offset</fsummary> + <desc> + <p><marker id="system_flag_time_offset"></marker> + Finalizes the <seealso marker="#time_offset/0">time offset</seealso> + when <seealso marker="time_correction#Single_Time_Warp_Mode">single + time warp mode</seealso> is used. If another time warp mode + is used, the time offset state is left unchanged.</p> + <p>Returns the old state identifier. That is:</p> + <list> + <item><p>If <c>preliminary</c> is returned, finalization was + performed and the time offset is now final.</p></item> + + <item><p>If <c>final</c> is returned, the time offset was + already in the final state. This either because another + <c>erlang:system_flag(time_offset, finalize)</c> call, or + because <seealso marker="time_correction#No_Time_Warp_Mode">no + time warp mode</seealso> is used.</p></item> + + <item><p>If <c>volatile</c> is returned, the time offset + cannot be finalized because + <seealso marker="time_correction#Multi_Time_Warp_Mode">multi + time warp mode</seealso> is used.</p></item> + </list> + </desc> + </func> + <func> <name name="system_info" arity="1" clause_i="1"/> <name name="system_info" arity="1" clause_i="2"/> <name name="system_info" arity="1" clause_i="3"/> <name name="system_info" arity="1" clause_i="4"/> <name name="system_info" arity="1" clause_i="5"/> + <fsummary>Information about the system allocators.</fsummary> <type variable="Allocator" name_i="2"/> <type variable="Version" name_i="2"/> <type variable="Features" name_i="2"/> <type variable="Settings" name_i="2"/> <type variable="Alloc" name_i="3"/> - <fsummary>Information about the allocators of the system</fsummary> <desc> - <p> - Returns various information about the - <marker id="system_info_allocator_tags">allocators</marker> of the + <marker id="system_info_allocator_tags"></marker> + <p>Returns various information about the allocators of the current system (emulator) as specified by <c><anno>Item</anno></c>:</p> + <marker id="system_info_allocated_areas"></marker> <taglist> - <tag><marker id="system_info_allocated_areas"><c>allocated_areas</c></marker></tag> + <tag><c>allocated_areas</c></tag> <item> <p>Returns a list of tuples with information about miscellaneous allocated memory areas.</p> - <p>Each tuple contains an atom describing type of memory as - first element and amount of allocated memory in bytes as - second element. In those cases when there is information - present about allocated and used memory, a third element - is present. This third element contains the amount of + <p>Each tuple contains an atom describing the type of + memory as first element and the amount of allocated + memory in bytes as second element. When information + about allocated and used memory is present, also a + third element is present, containing the amount of used memory in bytes.</p> <p><c>erlang:system_info(allocated_areas)</c> is intended - for debugging, and the content is highly implementation - dependent. The content of the results will therefore - change when needed without prior notice.</p> - <p><em>Note:</em> The sum of these values is <em>not</em> + for debugging, and the content is highly + implementation-dependent. The content of the results + therefore changes when needed without prior notice.</p> + <p>Notice that the sum of these values is <em>not</em> the total amount of memory allocated by the emulator. Some values are part of other values, and some memory - areas are not part of the result. If you are interested - in the total amount of memory allocated by the emulator - see <seealso marker="#memory/0">erlang:memory/0,1</seealso>.</p> + areas are not part of the result. For information about + the total amount of memory allocated by the emulator, see + <seealso marker="#memory/0">erlang:memory/0,1</seealso>.</p> </item> - <tag><marker id="system_info_allocator"><c>allocator</c></marker></tag> + <tag><c>allocator</c></tag> <item> - <p>Returns <c>{<anno>Allocator</anno>, <anno>Version</anno>, <anno>Features</anno>, <anno>Settings</anno>}.</c></p> - <p>Explanation:</p> + <marker id="system_info_allocator"></marker> + <p>Returns <c>{<anno>Allocator</anno>, <anno>Version</anno>, + <anno>Features</anno>, <anno>Settings</anno></c>, where:</p> <list type="bulleted"> <item> - <p><c><anno>Allocator</anno></c> corresponds to the <c>malloc()</c> - implementation used. If <c><anno>Allocator</anno></c> equals + <p><c><anno>Allocator</anno></c> corresponds to the + <c>malloc()</c> implementation used. If + <c><anno>Allocator</anno></c> equals <c>undefined</c>, the <c>malloc()</c> implementation - used could not be identified. Currently - <c>glibc</c> can be identified.</p> + used cannot be identified. <c>glibc</c> can be + identified.</p> </item> <item> - <p><c><anno>Version</anno></c> is a list of integers (but not a - string) representing the version of + <p><c><anno>Version</anno></c> is a list of integers + (but not a string) representing the version of the <c>malloc()</c> implementation used.</p> </item> <item> - <p><c><anno>Features</anno></c> is a list of atoms representing - allocation features used.</p> + <p><c><anno>Features</anno></c> is a list of atoms + representing the allocation features used.</p> </item> <item> - <p><c><anno>Settings</anno></c> is a list of subsystems, their - configurable parameters, and used values. Settings - may differ between different combinations of + <p><c><anno>Settings</anno></c> is a list of subsystems, + their configurable parameters, and used values. Settings + can differ between different combinations of platforms, allocators, and allocation features. Memory sizes are given in bytes.</p> </item> @@ -5404,165 +6502,169 @@ ok <p>See also "System Flags Effecting erts_alloc" in <seealso marker="erts:erts_alloc#flags">erts_alloc(3)</seealso>.</p> </item> - <tag><marker id="system_info_alloc_util_allocators"><c>alloc_util_allocators</c></marker></tag> + <tag><c>alloc_util_allocators</c></tag> <item> - <p>Returns a list of the names of all allocators - using the ERTS internal <c>alloc_util</c> framework - as atoms. For more information see the - <seealso marker="erts:erts_alloc#alloc_util">"the - alloc_util framework" section in the - erts_alloc(3)</seealso> documentation. - </p> + <marker id="system_info_alloc_util_allocators"></marker> + <p>Returns a list of the names of all allocators using + the <c>ERTS</c> internal <c>alloc_util</c> framework + as atoms. For more information, see Section + <seealso marker="erts:erts_alloc#alloc_util">"The + alloc_util framework" in erts_alloc(3)</seealso>.</p> </item> - <tag><marker id="system_info_allocator_tuple"><c>{allocator, <anno>Alloc</anno>}</c></marker></tag> + <tag><c>{allocator, <anno>Alloc</anno>}</c></tag> <item> + <marker id="system_info_allocator_tuple"></marker> <p>Returns information about the specified allocator. - As of erts version 5.6.1 the return value is a list - of <c>{instance, InstanceNo, InstanceInfo}</c> tuples + As from <c>ERTS</c> 5.6.1, the return value is a list + of <c>{instance, InstanceNo, InstanceInfo}</c> tuples, where <c>InstanceInfo</c> contains information about - a specific instance of the allocator. As of erts version - 5.10.4 the returned list when calling + a specific instance of the allocator. As from + <c>ERTS</c> 5.10.4, the returned list when calling <c>erlang:system_info({allocator, mseg_alloc})</c> also - include an <c>{erts_mmap, _}</c> tuple as one element - in the list. - If <c><anno>Alloc</anno></c> is not a recognized allocator, - <c>undefined</c> is returned. If <c><anno>Alloc</anno></c> is disabled, + includes an <c>{erts_mmap, _}</c> tuple as one element + in the list. If <c><anno>Alloc</anno></c> is not a + recognized allocator, <c>undefined</c> is returned. + If <c><anno>Alloc</anno></c> is disabled, <c>false</c> is returned.</p> - <p><em>Note:</em> The information returned is highly - implementation dependent and may be changed, or removed + <p>Notice that the information returned is highly + implementation-dependent and can be changed or removed at any time without prior notice. It was initially intended as a tool when developing new allocators, but - since it might be of interest for others it has been + as it can be of interest for others it has been briefly documented.</p> <p>The recognized allocators are listed in <seealso marker="erts:erts_alloc">erts_alloc(3)</seealso>. After reading the <c>erts_alloc(3)</c> documentation, the returned information - should more or less speak for itself. But it can be worth + more or less speaks for itself, but it can be worth explaining some things. Call counts are presented by two - values. The first value is giga calls, and the second - value is calls. <c>mbcs</c>, and <c>sbcs</c> are - abbreviations for, respectively, multi-block carriers, and - single-block carriers. Sizes are presented in bytes. When - it is not a size that is presented, it is the amount of - something. Sizes and amounts are often presented by three - values, the first is current value, the second is maximum - value since the last call to - <c>erlang:system_info({allocator, Alloc})</c>, and - the third is maximum value since the emulator was started. - If only one value is present, it is the current value. + values, the first value is giga calls, and the second + value is calls. <c>mbcs</c> and <c>sbcs</c> denote + multi-block carriers, and single-block carriers, + respectively. Sizes are presented in bytes. When a + size is not presented, it is the amount of something. + Sizes and amounts are often presented by three values:</p> + <list type="bulleted"> + <item>The first is the current value.</item> + <item>The second is the maximum value since the last call + to <c>erlang:system_info({allocator, Alloc})</c>.</item> + <item>The third is the maximum value since the emulator + was started.</item> + </list> + <p>If only one value is present, it is the current value. <c>fix_alloc</c> memory block types are presented by two - values. The first value is memory pool size and - the second value used memory size.</p> + values. The first value is the memory pool size and + the second value is the used memory size.</p> </item> - <tag><marker id="system_info_allocator_sizes"><c>{allocator_sizes, <anno>Alloc</anno>}</c></marker></tag> + <tag><c>{allocator_sizes, <anno>Alloc</anno>}</c></tag> <item> + <marker id="system_info_allocator_sizes"></marker> <p>Returns various size information for the specified allocator. The information returned is a subset of the information returned by - <seealso marker="#system_info_allocator_tuple">erlang:system_info({allocator, <anno>Alloc</anno>})</seealso>. + <seealso marker="#system_info_allocator_tuple"><c>erlang:system_info({allocator, <anno>Alloc</anno>})</c></seealso>. </p> </item> </taglist> </desc> </func> + <func> <name name="system_info" arity="1" clause_i="10"/> <name name="system_info" arity="1" clause_i="11"/> + <fsummary>Information about the CPU topology of the system.</fsummary> <type name="cpu_topology"/> <type name="level_entry"/> <type_desc name="cpu_topology"> - <marker id="system_info_cpu_topology"></marker> All <c><anno>LevelEntry</anno></c>s of a list must contain the same <c><anno>LevelTag</anno></c>, except on the top level where both <c>node</c> and - <c>processor</c> <c><anno>LevelTag</anno></c>s may co-exist. + <c>processor</c> <c><anno>LevelTag</anno></c>s can coexist. </type_desc> <type_desc name="level_entry"> - <c>{<anno>LevelTag</anno>, <anno>SubLevel</anno>} == {<anno>LevelTag</anno>, [], <anno>SubLevel</anno>}</c> + <c>{<anno>LevelTag</anno>, + <anno>SubLevel</anno>} == {<anno>LevelTag</anno>, [], + <anno>SubLevel</anno>}</c> </type_desc> <type name="level_tag"/> <type_desc name="level_tag"> - More <c><anno>LevelTag</anno></c>s may be introduced in the future. + More <c><anno>LevelTag</anno></c>s can be introduced in a + future release. </type_desc> <type name="sub_level"/> <type name="info_list"/> <type_desc name="info_list"> - The <c>info_list()</c> may be extended in the future. + The <c>info_list()</c> can be extended in a future release. </type_desc> - <fsummary>Information about the CPU topology of the system</fsummary> <desc> - <p>Returns various information about the - <marker id="system_info_cpu_topology_tags">CPU topology</marker> - of the current system - (emulator) as specified by <c><anno>Item</anno></c>:</p> + <marker id="system_info_cpu_topology_tags"></marker> + <marker id="system_info_cpu_topology"></marker> + <p>Returns various information about the CPU topology of + the current system (emulator) as specified by + <c><anno>Item</anno></c>:</p> <taglist> <tag><c>cpu_topology</c></tag> <item> - <p>Returns the <c><anno>CpuTopology</anno></c> which currently is used by the - emulator. The CPU topology is used when binding schedulers + <p>Returns the <c><anno>CpuTopology</anno></c> currently used by + the emulator. The CPU topology is used when binding schedulers to logical processors. The CPU topology used is the - <seealso marker="erlang#system_info_cpu_topology_defined">user - defined CPU topology</seealso> if such exists; otherwise, the - <seealso marker="erlang#system_info_cpu_topology_detected">automatically - detected CPU topology</seealso> if such exists. If no CPU topology + <seealso marker="erlang#system_info_cpu_topology_defined">user-defined CPU topology</seealso>, + if such exists, otherwise the + <seealso marker="erlang#system_info_cpu_topology_detected">automatically detected CPU topology</seealso>, + if such exists. If no CPU topology exists, <c>undefined</c> is returned.</p> - <p><c>node</c> refers to NUMA (non-uniform memory access) - nodes, and <c>thread</c> refers to hardware threads - (e.g. Intels hyper-threads).</p> - <p>A level in the <c><anno>CpuTopology</anno></c> term can be omitted if - only one entry exists and the <c><anno>InfoList</anno></c> is empty. - </p> + <p><c>node</c> refers to Non-Uniform Memory Access (NUMA) + nodes. <c>thread</c> refers to hardware threads + (for example, Intel hyper-threads).</p> + <p>A level in term <c><anno>CpuTopology</anno></c> can be + omitted if only one entry exists and + <c><anno>InfoList</anno></c> is empty.</p> <p><c>thread</c> can only be a sub level to <c>core</c>. - <c>core</c> can be a sub level to either <c>processor</c> - or <c>node</c>. <c>processor</c> can either be on the + <c>core</c> can be a sub level to <c>processor</c> + or <c>node</c>. <c>processor</c> can be on the top level or a sub level to <c>node</c>. <c>node</c> - can either be on the top level or a sub level to + can be on the top level or a sub level to <c>processor</c>. That is, NUMA nodes can be processor internal or processor external. A CPU topology can consist of a mix of processor internal and external - NUMA nodes, as long as each logical CPU belongs to one - and only one NUMA node. Cache hierarchy is not part of - the <c><anno>CpuTopology</anno></c> type yet, but will be in the - future. Other things may also make it into the CPU - topology in the future. In other words, expect the - <c><anno>CpuTopology</anno></c> type to change. - </p> - </item> - <tag><marker id="system_info_cpu_topology_defined"><c>{cpu_topology, defined}</c></marker></tag> - <item> - <p>Returns the user defined <c><anno>CpuTopology</anno></c>. For more - information see the documentation of - the <c>erl</c> <seealso marker="erts:erl#+sct">+sct</seealso> command - line flag, and the documentation of the - <seealso marker="#system_info_cpu_topology">cpu_topology</seealso> - argument. - </p> - </item> - <tag><marker id="system_info_cpu_topology_detected"><c>{cpu_topology, detected}</c></marker></tag> - <item> - <p>Returns the automatically detected <c><anno>CpuTopology</anno></c>. The - emulator currently only detects the CPU topology on some newer - Linux, Solaris, FreeBSD, and Windows systems. On Windows system with - more than 32 logical processors the CPU topology is not detected. - </p> - <p>For more information see the documentation of the - <seealso marker="#system_info_cpu_topology">cpu_topology</seealso> - argument. - </p> + NUMA nodes, as long as each logical CPU belongs to + <em>one</em> NUMA node. Cache hierarchy is not part of + the <c><anno>CpuTopology</anno></c> type, but will be in a + future release. Other things can also make it into the CPU + topology in a future release. In other words, expect the + <c><anno>CpuTopology</anno></c> type to change.</p> + </item> + <tag><c>{cpu_topology, defined}</c></tag> + <item> + <marker id="system_info_cpu_topology_defined"></marker> + <p>Returns the user-defined <c><anno>CpuTopology</anno></c>. + For more information, see command-line flag + <seealso marker="erts:erl#+sct">+sct</seealso> in + <c>erl(1)</c> and argument + <seealso marker="#system_info_cpu_topology">cpu_topology</seealso>.</p> + </item> + <tag><c>{cpu_topology, detected}</c></tag> + <item> + <marker id="system_info_cpu_topology_detected"></marker> + <p>Returns the automatically detected + <c><anno>CpuTopology</anno>y</c>. The + emulator detects the CPU topology on some newer + Linux, Solaris, FreeBSD, and Windows systems. + On Windows system with more than 32 logical processors, + the CPU topology is not detected.</p> + <p>For more information, see argument + <seealso marker="#system_info_cpu_topology">cpu_topology</seealso>.</p> </item> <tag><c>{cpu_topology, used}</c></tag> <item> - <p>Returns the <c><anno>CpuTopology</anno></c> which is used by the - emulator. For more information see the - documentation of the - <seealso marker="#system_info_cpu_topology">cpu_topology</seealso> - argument. - </p> + <p>Returns <c><anno>CpuTopology</anno></c> used by the emulator. + For more information, see argument + <seealso marker="#system_info_cpu_topology">cpu_topology</seealso>.</p> </item> </taglist> </desc> </func> + <func> <name name="system_info" arity="1" clause_i="6"/> <name name="system_info" arity="1" clause_i="7"/> @@ -5612,7 +6714,19 @@ ok <name name="system_info" arity="1" clause_i="53"/> <name name="system_info" arity="1" clause_i="54"/> <name name="system_info" arity="1" clause_i="55"/> - <fsummary>Information about the system</fsummary> + <name name="system_info" arity="1" clause_i="56"/> + <name name="system_info" arity="1" clause_i="57"/> + <name name="system_info" arity="1" clause_i="58"/> + <name name="system_info" arity="1" clause_i="59"/> + <name name="system_info" arity="1" clause_i="60"/> + <name name="system_info" arity="1" clause_i="61"/> + <name name="system_info" arity="1" clause_i="62"/> + <name name="system_info" arity="1" clause_i="63"/> + <name name="system_info" arity="1" clause_i="64"/> + <name name="system_info" arity="1" clause_i="65"/> + <name name="system_info" arity="1" clause_i="66"/> + <name name="system_info" arity="1" clause_i="67"/> + <fsummary>Information about the system.</fsummary> <desc> <p>Returns various information about the current system (emulator) as specified by <c><anno>Item</anno></c>:</p> @@ -5629,8 +6743,7 @@ ok Other possible return values are <c>debug</c>, <c>purify</c>, <c>quantify</c>, <c>purecov</c>, <c>gcov</c>, <c>valgrind</c>, <c>gprof</c>, and <c>lcnt</c>. Possible return values - may be added and/or removed at any time without prior notice. - </p> + can be added or removed at any time without prior notice.</p> </item> <tag><c>c_compiler_used</c></tag> <item> @@ -5638,26 +6751,25 @@ ok compiling the runtime system. The first element is an atom describing the name of the compiler, or <c>undefined</c> if unknown. The second element is a term describing the - version of the compiler, or <c>undefined</c> if unknown. - </p> + version of the compiler, or <c>undefined</c> if unknown.</p> </item> <tag><c>check_io</c></tag> <item> <p>Returns a list containing miscellaneous information - regarding the emulators internal I/O checking. Note, - the content of the returned list may vary between - platforms and over time. The only thing guaranteed is + about the emulators internal I/O checking. Notice that + the content of the returned list can vary between + platforms and over time. It is only guaranteed that a list is returned.</p> </item> <tag><c>compat_rel</c></tag> <item> <p>Returns the compatibility mode of the local node as an integer. The integer returned represents the - Erlang/OTP release which the current emulator has been + Erlang/OTP release that the current emulator has been set to be backward compatible with. The compatibility - mode can be configured at startup by using the command - line flag <c>+R</c>, see - <seealso marker="erts:erl#compat_rel">erl(1)</seealso>.</p> + mode can be configured at startup by using command-line flag + <seealso marker="erts:erl#compat_rel">+R</seealso> in + <c>erl(1)</c>.</p> </item> <tag><c>cpu_topology</c></tag> <item> @@ -5670,110 +6782,200 @@ ok creation of a node is stored in process identifiers, port identifiers, and references. This makes it (to some extent) possible to distinguish between identifiers from - different incarnations of a node. Currently valid - creations are integers in the range 1..3, but this may - (probably will) change in the future. If the node is not - alive, 0 is returned.</p> + different incarnations of a node. The valid + creations are integers in the range 1..3, but this will + probably change in a future release. If the node is not + alive, <c>0</c> is returned.</p> </item> <tag><c>debug_compiled</c></tag> <item> <p>Returns <c>true</c> if the emulator has been debug - compiled; otherwise, <c>false</c>. - </p> + compiled, otherwise <c>false</c>.</p> + </item> + <tag><c>delayed_node_table_gc</c></tag> + <item> + <marker id="system_info_delayed_node_table_gc"></marker> + <p>Returns the amount of time in seconds garbage collection + of an entry in a node table is delayed. This limit can be set + on startup by passing the command line flag + <seealso marker="erts:erl#+zdntgc">+zdntgc</seealso> + to <c>erl</c>. For more information see the documentation of the + command line flag.</p> + </item> + <tag><c>dirty_cpu_schedulers</c></tag> + <item> + <marker id="system_info_dirty_cpu_schedulers"></marker> + <p>Returns the number of dirty CPU scheduler threads used by + the emulator. Dirty CPU schedulers execute CPU-bound + native functions, such as NIFs, linked-in driver code, + and BIFs that cannot be managed cleanly by the normal + emulator schedulers.</p> + <p>The number of dirty CPU scheduler threads is determined + at emulator boot time and cannot be changed after that. + However, the number of dirty CPU scheduler threads online + can be changed at any time. The number of dirty CPU + schedulers can be set at startup by passing + command-line flag + <seealso marker="erts:erl#+SDcpu">+SDcpu</seealso> or + <seealso marker="erts:erl#+SDPcpu">+SDPcpu</seealso> in + <c>erl(1)</c>.</p> + <p>Notice that the dirty schedulers functionality is + experimental. Enable support for dirty schedulers when + building OTP to try out the functionality.</p> + <p>See also + <seealso marker="#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>, + <seealso marker="#system_info_dirty_cpu_schedulers_online">erlang:system_info(dirty_cpu_schedulers_online)</seealso>, + <seealso marker="#system_info_dirty_io_schedulers">erlang:system_info(dirty_io_schedulers)</seealso>, + <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>, + <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>, and + <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>.</p> + </item> + <tag><c>dirty_cpu_schedulers_online</c></tag> + <item> + <marker id="system_info_dirty_cpu_schedulers_online"></marker> + <p>Returns the number of dirty CPU schedulers online. + The return value satisfies + <c><![CDATA[1 <= DirtyCPUSchedulersOnline <= N]]></c>, + where <c>N</c> is the smallest of the return values of + <c>erlang:system_info(dirty_cpu_schedulers)</c> and + <c>erlang:system_info(schedulers_online)</c>.</p> + <p>The number of dirty CPU schedulers online can be set at + startup by passing command-line flag + <seealso marker="erts:erl#+SDcpu">+SDcpu</seealso> in + <c>erl(1)</c>.</p> + <p>Notice that the dirty schedulers functionality is + experimental. Enable support for dirty schedulers when + building OTP to try out the functionality.</p> + <p>For more information, see + <seealso marker="#system_info_dirty_cpu_schedulers">erlang:system_info(dirty_cpu_schedulers)</seealso>, + <seealso marker="#system_info_dirty_io_schedulers">erlang:system_info(dirty_io_schedulers)</seealso>, + <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>, and + <seealso marker="#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>.</p> + </item> + <tag><c>dirty_io_schedulers</c></tag> + <item> + <marker id="system_info_dirty_io_schedulers"></marker> + <p>Returns the number of dirty I/O schedulers as an integer. + Dirty I/O schedulers execute I/O-bound native functions, + such as NIFs and linked-in driver code, which cannot be + managed cleanly by the normal emulator schedulers.</p> + <p>This value can be set at startup by passing command-line + argument <seealso marker="erts:erl#+SDio">+SDio</seealso> + in <c>erl(1)</c>.</p> + <p>Notice that the dirty schedulers functionality is + experimental. Enable support for dirty schedulers when + building OTP to try out the functionality.</p> + <p>For more information, see + <seealso marker="#system_info_dirty_cpu_schedulers">erlang:system_info(dirty_cpu_schedulers)</seealso>, + <seealso marker="#system_info_dirty_cpu_schedulers_online">erlang:system_info(dirty_cpu_schedulers_online)</seealso>, and + <seealso marker="#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>.</p> </item> <tag><c>dist</c></tag> <item> <p>Returns a binary containing a string of distribution information formatted as in Erlang crash dumps. For more - information see the <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> - chapter in the ERTS User's Guide.</p> + information, see Section + <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> + in the User's Guide.</p> </item> - <tag><marker id="system_info_dist_buf_busy_limit"><c>dist_buf_busy_limit</c></marker></tag> + <tag><c>dist_buf_busy_limit</c></tag> <item> + <marker id="system_info_dist_buf_busy_limit"></marker> <p>Returns the value of the distribution buffer busy limit - in bytes. This limit can be set on startup by passing the - <seealso marker="erts:erl#+zdbbl">+zdbbl</seealso> command line - flag to <c>erl</c>.</p> + in bytes. This limit can be set at startup by passing + command-line flag + <seealso marker="erts:erl#+zdbbl">+zdbbl</seealso> + to <c>erl</c>.</p> </item> <tag><c>dist_ctrl</c></tag> <item> <p>Returns a list of tuples - <c>{Node, ControllingEntity}</c>, one entry for each - connected remote node. The <c><anno>Node</anno></c> is the name of the - node and the <c><anno>ControllingEntity</anno></c> is the port or pid - responsible for the communication to that node. More - specifically, the <c><anno>ControllingEntity</anno></c> for nodes - connected via TCP/IP (the normal case) is the socket - actually used in communication with the specific node.</p> + <c>{<anno>Node</anno>, <anno>ControllingEntity</anno>}</c>, + one entry for each connected remote node. + <c><anno>Node</anno></c> is the node name + and <c><anno>ControllingEntity</anno></c> is the port or process + identifier responsible for the communication to that node. + More specifically, <c><anno>ControllingEntity</anno></c> for + nodes connected through TCP/IP (the normal case) is the socket + used in communication with the specific node.</p> </item> <tag><c>driver_version</c></tag> <item> - <p>Returns a string containing the erlang driver version - used by the runtime system. It will be on the form + <p>Returns a string containing the Erlang driver version + used by the runtime system. It has the form <seealso marker="erts:erl_driver#version_management">"<major ver>.<minor ver>"</seealso>.</p> </item> <tag><c>dynamic_trace</c></tag> <item> <p>Returns an atom describing the dynamic trace framework - compiled into the virtual machine. It can currently be either - <c>dtrace</c>, <c>systemtap</c> or <c>none</c>. For a - commercial or standard build, this is always <c>none</c>, - the other return values indicate a custom configuration - (e.g. <c>./configure --with-dynamic-trace=dtrace</c>). See - the <seealso marker="runtime_tools:dyntrace">dyntrace - </seealso> manual page and the + compiled into the virtual machine. It can be + <c>dtrace</c>, <c>systemtap</c>, or <c>none</c>. For a + commercial or standard build, it is always <c>none</c>. + The other return values indicate a custom configuration + (for example, <c>./configure --with-dynamic-trace=dtrace</c>). + For more information about dynamic tracing, see the + <seealso marker="runtime_tools:dyntrace">dyntrace</seealso> + manual page and the <c>README.dtrace</c>/<c>README.systemtap</c> files in the - Erlang source code top directory for more information - about dynamic tracing.</p> + Erlang source code top directory.</p> </item> <tag><c>dynamic_trace_probes</c></tag> <item> - <p>Returns a <c>boolean()</c> indicating if dynamic trace probes - (either dtrace or systemtap) are built into the - emulator. This can only be <c>true</c> if the virtual - machine was built for dynamic tracing - (i.e. <c>system_info(dynamic_trace)</c> returns + <p>Returns a <c>boolean()</c> indicating if dynamic trace + probes (<c>dtrace</c> or <c>systemtap</c>) are built into + the emulator. This can only be <c>true</c> if the Virtual + Machine was built for dynamic tracing (that is, + <c>system_info(dynamic_trace)</c> returns <c>dtrace</c> or <c>systemtap</c>).</p> </item> + <tag><marker id="system_info_end_time"/><c>end_time</c></tag> + <item><p>The last <seealso marker="#monotonic_time/0">Erlang monotonic + time</seealso> in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso> that + can be represented internally in the current Erlang runtime system + instance. The time between the + <seealso marker="#system_info_start_time">start time</seealso> and + the end time is at least a quarter of a millennium.</p></item> <tag><c>elib_malloc</c></tag> <item> <p>This option will be removed in a future release. - The return value will always be <c>false</c> since - the elib_malloc allocator has been removed.</p> + The return value will always be <c>false</c>, as the + <c>elib_malloc</c> allocator has been removed.</p> </item> - <tag><marker id="system_info_eager_check_io"><c>eager_check_io</c></marker></tag> + <tag><marker id="system_info_eager_check_io"/><c>eager_check_io</c></tag> <item> <p> - Returns the value of the <c>erl</c> - <seealso marker="erl#+secio">+secio</seealso> command line - flag which is either <c>true</c> or <c>false</c>. See the + Returns the value of the <c>erl</c> command line flag + <seealso marker="erl#+secio">+secio</seealso> + which is either <c>true</c> or <c>false</c>. See the documentation of the command line flag for information about the different values. </p> </item> <tag><c>ets_limit</c></tag> <item> - <p>Returns the maximum number of ETS tables allowed. This limit - can be increased on startup by passing the <seealso - marker="erts:erl#+e">+e</seealso> command line flag to - <c>erl</c> or by setting the environment variable - <c>ERL_MAX_ETS_TABLES</c> before starting the Erlang runtime - system.</p> + <p>Returns the maximum number of ETS tables allowed. This + limit can be increased at startup by passing + command-line flag + <seealso marker="erts:erl#+e">+e</seealso> to + <c>erl(1)</c> or by setting environment variable + <c>ERL_MAX_ETS_TABLES</c> before starting the Erlang + runtime system.</p> </item> <tag><c>fullsweep_after</c></tag> <item> - <p>Returns <c>{fullsweep_after, integer() >= 0}</c> which is the - <c>fullsweep_after</c> garbage collection setting used - by default. For more information see - <c>garbage_collection</c> described below.</p> + <p>Returns <c>{fullsweep_after, integer() >= 0}</c>, which is + the <c>fullsweep_after</c> garbage collection setting used + by default. For more information, see + <c>garbage_collection</c> described in the following.</p> </item> <tag><c>garbage_collection</c></tag> <item> <p>Returns a list describing the default garbage collection settings. A process spawned on the local node by a - <c>spawn</c> or <c>spawn_link</c> will use these + <c>spawn</c> or <c>spawn_link</c> uses these garbage collection settings. The default settings can be - changed by use of + changed by using <seealso marker="#system_flag/2">system_flag/2</seealso>. <seealso marker="#spawn_opt/4">spawn_opt/4</seealso> can spawn a process that does not use the default @@ -5787,8 +6989,8 @@ ok </item> <tag><c>heap_type</c></tag> <item> - <p>Returns the heap type used by the current emulator. - Currently only the following heap type exists:</p> + <p>Returns the heap type used by the current emulator. One + heap type exists:</p> <taglist> <tag><c>private</c></tag> <item> @@ -5803,51 +7005,51 @@ ok <item> <p>Returns a binary containing a string of miscellaneous system information formatted as in Erlang crash dumps. - For more information see the - <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> chapter in the ERTS - User's Guide.</p> + For more information, see Section + <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> + in the User's Guide.</p> </item> <tag><c>kernel_poll</c></tag> <item> <p>Returns <c>true</c> if the emulator uses some kind of - kernel-poll implementation; otherwise, <c>false</c>.</p> + kernel-poll implementation, otherwise <c>false</c>.</p> </item> <tag><c>loaded</c></tag> <item> <p>Returns a binary containing a string of loaded module information formatted as in Erlang crash dumps. For more - information see the <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> chapter - in the ERTS User's Guide.</p> + information, see Section + <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> + in the User's Guide.</p> </item> - <tag><marker id="logical_processors"><c>logical_processors</c></marker></tag> + <tag><c>logical_processors</c></tag> <item> + <marker id="logical_processors"></marker> <p>Returns the detected number of logical processors configured - on the system. The return value is either an integer, or - the atom <c>unknown</c> if the emulator wasn't able to - detect logical processors configured. - </p> + in the system. The return value is either an integer, or + the atom <c>unknown</c> if the emulator cannot + detect the configured logical processors.</p> </item> - <tag><marker id="logical_processors_available"><c>logical_processors_available</c></marker></tag> + <tag><c>logical_processors_available</c></tag> <item> - <p>Returns the detected number of logical processors available to - the Erlang runtime system. The return value is either an - integer, or the atom <c>unknown</c> if the emulator wasn't - able to detect logical processors available. The number - of logical processors available is less than or equal to - the number of <seealso marker="#logical_processors_online">logical - processors online</seealso>. - </p> + <marker id="logical_processors_available"></marker> + <p>Returns the detected number of logical processors available + to the Erlang runtime system. The return value is either an + integer, or the atom <c>unknown</c> if the emulator + cannot detect the available logical processors. The number + of available logical processors is less than or equal to + the number of + <seealso marker="#logical_processors_online">logical processors online</seealso>.</p> </item> - <tag><marker id="logical_processors_online"><c>logical_processors_online</c></marker></tag> + <tag><c>logical_processors_online</c></tag> <item> + <marker id="logical_processors_online"></marker> <p>Returns the detected number of logical processors online on the system. The return value is either an integer, - or the atom <c>unknown</c> if the emulator wasn't able to + or the atom <c>unknown</c> if the emulator cannot detect logical processors online. The number of logical processors online is less than or equal to the number of - <seealso marker="#logical_processors">logical processors - configured</seealso>. - </p> + <seealso marker="#logical_processors">logical processors configured</seealso>.</p> </item> <tag><c>machine</c></tag> <item> @@ -5855,27 +7057,30 @@ ok </item> <tag><c>min_heap_size</c></tag> <item> - <p>Returns <c>{min_heap_size, <anno>MinHeapSize</anno>}</c> where <c><anno>MinHeapSize</anno></c> is the current system wide - minimum heap size for spawned processes.</p> + <p>Returns <c>{min_heap_size, <anno>MinHeapSize</anno>}</c>, + where <c><anno>MinHeapSize</anno></c> is the current + system-wide minimum heap size for spawned processes.</p> </item> <tag><c>min_bin_vheap_size</c></tag> <item> - <p>Returns <c>{min_bin_vheap_size, <anno>MinBinVHeapSize</anno>}</c> where <c><anno>MinBinVHeapSize</anno></c> is the current system wide + <p>Returns <c>{min_bin_vheap_size, + <anno>MinBinVHeapSize</anno>}</c>, where + <c><anno>MinBinVHeapSize</anno></c> is the current system-wide minimum binary virtual heap size for spawned processes.</p> </item> <tag><c>modified_timing_level</c></tag> <item> - <p>Returns the modified timing level (an integer) if - modified timing has been enabled; otherwise, - <c>undefined</c>. See the <c>+T</c> command line flag - in the documentation of the - <seealso marker="erts:erl#+T">erl(1)</seealso> - command for more information on modified timing.</p> + <p>Returns the modified timing-level (an integer) if + modified timing is enabled, otherwise, <c>undefined</c>. + For more information about modified timing, see + command-line flag + <seealso marker="erts:erl#+T">+T</seealso> + in <c>erl(1)</c></p> </item> - <tag><marker id="system_info_multi_scheduling"><c>multi_scheduling</c></marker></tag> + <tag><c>multi_scheduling</c></tag> <item> - <p>Returns <c>disabled</c>, <c>blocked</c>, or <c>enabled</c>. - A description of the return values:</p> + <marker id="system_info_multi_scheduling"></marker> + <p>Returns <c>disabled</c>, <c>blocked</c>, or <c>enabled</c>:</p> <taglist> <tag><c>disabled</c></tag> <item> @@ -5886,167 +7091,317 @@ ok <tag><c>blocked</c></tag> <item> <p>The emulator has more than one scheduler thread, - but all scheduler threads but one have been blocked, - i.e., only one scheduler thread will schedule - Erlang processes and execute Erlang code.</p> + but all scheduler threads except one are blocked, + that is, only one scheduler thread schedules + Erlang processes and executes Erlang code.</p> </item> <tag><c>enabled</c></tag> <item> <p>The emulator has more than one scheduler thread, - and no scheduler threads have been blocked, i.e., - all available scheduler threads will schedule + and no scheduler threads are blocked, that is, + all available scheduler threads schedule Erlang processes and execute Erlang code.</p> </item> </taglist> - <p>See also <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>, - <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>, and + <p>See also + <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>, + <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>, + and <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p> </item> - <tag><marker id="system_info_multi_scheduling_blockers"><c>multi_scheduling_blockers</c></marker></tag> + <tag><c>multi_scheduling_blockers</c></tag> <item> - <p>Returns a list of <c><anno>PID</anno></c>s when multi-scheduling - is blocked; otherwise, the empty list. The <c><anno>PID</anno></c>s - in the list is <c><anno>PID</anno></c>s of the processes currently - blocking multi-scheduling. A <c><anno>PID</anno></c> will only be - present once in the list, even if the corresponding + <marker id="system_info_multi_scheduling_blockers"></marker> + <p>Returns a list of <c><anno>Pid</anno></c>s when + multi-scheduling is blocked, otherwise the empty list is + returned. The <c><anno>Pid</anno></c>s in the list + represent all the processes currently + blocking multi-scheduling. A <c><anno>Pid</anno></c> occurs + only once in the list, even if the corresponding process has blocked multiple times.</p> - <p>See also <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>, - <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, and + <p>See also + <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>, + <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, + and <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p> </item> - <tag><marker id="system_info_otp_release"><c>otp_release</c></marker></tag> + <tag><c>nif_version</c></tag> + <item> + <p>Returns a string containing the version of the Erlang NIF interface + used by the runtime system. It is on the form + "<major ver>.<minor ver>".</p> + </item> + <tag><c>otp_release</c></tag> + <item> + <marker id="system_info_otp_release"></marker> + <p>Returns a string containing the OTP release number of the + OTP release that the currently executing <c>ERTS</c> application is + part of.</p> + <p>As from OTP 17, the OTP release number corresponds to + the major OTP version number. No + <c>erlang:system_info()</c> argument gives the exact OTP + version. This is because the exact OTP version in the general case + is difficult to determine. For more information, see the description + of versions in <seealso marker="doc/system_principles:versions"> + System principles</seealso> in System Documentation.</p> + </item> + <tag><marker id="system_info_os_monotonic_time_source"/><c>os_monotonic_time_source</c></tag> + <item> + <p>Returns a list containing information about the source of + <seealso marker="erts:time_correction#OS_Monotonic_Time">OS + monotonic time</seealso> that is used by the runtime system.</p> + <p>If <c>[]</c> is returned, no OS monotonic time is + available. The list contains two-tuples with <c>Key</c>s + as first element, and <c>Value</c>s as second element. The + order of these tuples is undefined. The following + tuples can be part of the list, but more tuples can be + introduced in the future:</p> + <taglist> + <tag><c>{function, Function}</c></tag> + <item><p><c>Function</c> is the name of the function + used. This tuple always exist if OS monotonic time is + available to the runtime system.</p></item> + + <tag><c>{clock_id, ClockId}</c></tag> + <item><p>This tuple only exist if <c>Function</c> + can be used with different clocks. <c>ClockId</c> + corresponds to the clock identifier used when calling + <c>Function</c>.</p></item> + + <tag><c>{resolution, OsMonotonicTimeResolution}</c></tag> + <item><p>Highest possible + <seealso marker="time_correction#Time_Resolution">resolution</seealso> + of current OS monotonic time source as parts per + second. If no resolution information can be retrieved + from the OS, <c>OsMonotonicTimeResolution</c> is + set to the resolution of the time unit of + <c>Function</c>s return value. That is, the actual + resolution can be lower than + <c>OsMonotonicTimeResolution</c>. Also note that + the resolution does not say anything about the + <seealso marker="time_correction#Time_Accuracy">accuracy</seealso>, + and whether the + <seealso marker="time_correction#Time_Precision">precision</seealso> + do align with the resolution. You do, + however, know that the precision is not better than + <c>OsMonotonicTimeResolution</c>.</p></item> + + <tag><c>{extended, Extended}</c></tag> + <item><p><c>Extended</c> equals <c>yes</c> if + the range of time values has been extended; + otherwise, <c>Extended</c> equals <c>no</c>. The + range needs to be extended if <c>Function</c> + returns values that wrap fast. This typically + is the case when the return value is a 32-bit + value.</p></item> + + <tag><c>{parallel, Parallel}</c></tag> + <item><p><c>Parallel</c> equals <c>yes</c> if + <c>Function</c> is called in parallel from multiple + threads. If it is not called in parallel, because + calls needs to be serialized, <c>Parallel</c> equals + <c>no</c>.</p></item> + + <tag><c>{time, OsMonotonicTime}</c></tag> + <item><p><c>OsMonotonicTime</c> equals current OS + monotonic time in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso>.</p></item> + </taglist> + </item> + <tag><marker id="system_info_os_system_time_source"/><c>os_system_time_source</c></tag> <item> - <p>Returns a string containing the OTP release number.</p> + <p>Returns a list containing information about the source of + <seealso marker="erts:time_correction#OS_System_Time">OS + system time</seealso> that is used by the runtime system.</p> + <p>The list contains two-tuples with <c>Key</c>s + as first element, and <c>Value</c>s as second element. The + order if these tuples is undefined. The following + tuples can be part of the list, but more tuples can be + introduced in the future:</p> + <taglist> + <tag><c>{function, Function}</c></tag> + <item><p><c>Function</c> is the name of the funcion + used.</p></item> + + <tag><c>{clock_id, ClockId}</c></tag> + <item><p>This tuple only exist if <c>Function</c> + can be used with different clocks. <c>ClockId</c> + corresponds to the clock identifier used when calling + <c>Function</c>.</p></item> + + <tag><c>{resolution, OsSystemTimeResolution}</c></tag> + <item><p>Highest possible + <seealso marker="time_correction#Time_Resolution">resolution</seealso> + of current OS system time source as parts per + second. If no resolution information can be retrieved + from the OS, <c>OsSystemTimeResolution</c> is + set to the resolution of the time unit of + <c>Function</c>s return value. That is, the actual + resolution may be lower than + <c>OsSystemTimeResolution</c>. Also note that + the resolution does not say anything about the + <seealso marker="time_correction#Time_Accuracy">accuracy</seealso>, + and whether the + <seealso marker="time_correction#Time_Precision">precision</seealso> + do align with the resolution. You do, + however, know that the precision is not better than + <c>OsSystemTimeResolution</c>.</p></item> + + <tag><c>{parallel, Parallel}</c></tag> + <item><p><c>Parallel</c> equals <c>yes</c> if + <c>Function</c> is called in parallel from multiple + threads. If it is not called in parallel, because + calls needs to be serialized, <c>Parallel</c> equals + <c>no</c>.</p></item> + + <tag><c>{time, OsSystemTime}</c></tag> + <item><p><c>OsSystemTime</c> equals current OS + system time in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso>.</p></item> + </taglist> </item> - <tag><marker id="system_info_port_parallelism"><c>port_parallelism</c></marker></tag> - <item><p>Returns the default port parallelism scheduling hint used. - For more information see the - <seealso marker="erl#+spp">+spp</seealso> command line argument - of <seealso marker="erl">erl(1)</seealso>.</p></item> + <tag><c>port_parallelism</c></tag> + <item> + <marker id="system_info_port_parallelism"></marker> + <p>Returns the default port parallelism scheduling hint used. + For more information, see command-line argument + <seealso marker="erl#+spp">+spp</seealso> in <c>erl(1)</c>.</p></item> <tag><marker id="system_info_port_count"/><c>port_count</c></tag> <item> - <p>Returns the number of ports currently existing at - the local node as an integer. The same value as - <c>length(erlang:ports())</c> returns, but more efficient.</p> + <p>Returns the number of ports currently existing at the + local node. The value is given as an integer. This is + the same value as returned by + <c>length(erlang:ports())</c>, but more efficient.</p> </item> - <tag><marker id="system_info_port_limit"><c>port_limit</c></marker></tag> + <tag><c>port_limit</c></tag> <item> + <marker id="system_info_port_limit"></marker> <p>Returns the maximum number of simultaneously existing - ports at the local node as an integer. This limit - can be configured at startup by using the - <seealso marker="erl#+Q">+Q</seealso> - command line flag of - <seealso marker="erl">erl(1)</seealso>.</p> + ports at the local node as an integer. This limit can be + configured at startup by using command-line flag + <seealso marker="erl#+Q">+Q</seealso> in <c>erl(1)</c>.</p> </item> <tag><marker id="system_info_process_count"/><c>process_count</c></tag> <item> - <p>Returns the number of processes currently existing at - the local node as an integer. The same value as - <c>length(processes())</c> returns, but more efficient.</p> + <p>Returns the number of processes currently existing at the + local node. The value is given as an integer. This is + the same value as returned by + <c>length(processes())</c>, but more efficient.</p> </item> - <tag><marker id="system_info_process_limit"><c>process_limit</c></marker></tag> + <tag><c>process_limit</c></tag> <item> + <marker id="system_info_process_limit"></marker> <p>Returns the maximum number of simultaneously existing - processes at the local node as an integer. This limit - can be configured at startup by using the - <seealso marker="erl#+P">+P</seealso> - command line flag of - <seealso marker="erl">erl(1)</seealso>.</p> + processes at the local node. The value is given as an + integer. This limit can be configured at startup by using + command-line flag <seealso marker="erl#+P">+P</seealso> + in <c>erl(1)</c>.</p> </item> <tag><c>procs</c></tag> <item> <p>Returns a binary containing a string of process and port information formatted as in Erlang crash dumps. For more - information see the <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> chapter - in the ERTS User's Guide.</p> + information, see Section + <seealso marker="erts:crash_dump">"How to interpret the Erlang crash dumps"</seealso> + in the User's Guide.</p> </item> - <tag><marker id="system_info_scheduler_bind_type"><c>scheduler_bind_type</c></marker></tag> + <tag><c>scheduler_bind_type</c></tag> <item> - <p>Returns information on how user has requested + <marker id="system_info_scheduler_bind_type"></marker> + <p>Returns information about how the user has requested schedulers to be bound or not bound.</p> - <p><em>NOTE:</em> Even though user has requested - schedulers to be bound, they might have silently failed - to bind. In order to inspect actual scheduler bindings call - <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>. - </p> - <p>For more information, see - the <c>erl</c> <seealso marker="erts:erl#+sbt">+sbt</seealso> - command line argument, and - <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>. - </p> - </item> - <tag><marker id="system_info_scheduler_bindings"><c>scheduler_bindings</c></marker></tag> - <item> - <p>Returns information on currently used scheduler + <p>Notice that even though a user has requested + schedulers to be bound, they can silently have failed + to bind. To inspect the scheduler bindings, call + <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.</p> + <p>For more information, see command-line argument + <seealso marker="erts:erl#+sbt">+sbt</seealso> + in <c>erl(1)</c> and + <seealso marker="#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.</p> + </item> + <tag><c>scheduler_bindings</c></tag> + <item> + <marker id="system_info_scheduler_bindings"></marker> + <p>Returns information about the currently used scheduler bindings.</p> <p>A tuple of a size equal to - <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso> is returned. The elements of the tuple are integers + <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso> + is returned. The tuple elements are integers or the atom <c>unbound</c>. Logical processor identifiers are represented as integers. The <c>N</c>th element of the tuple equals the current binding for the scheduler with the scheduler identifier equal to - <c>N</c>. E.g., if the schedulers have been bound, + <c>N</c>. For example, if the schedulers are bound, <c>element(erlang:system_info(scheduler_id), - erlang:system_info(scheduler_bindings))</c> will return + erlang:system_info(scheduler_bindings))</c> returns the identifier of the logical processor that the calling - process is executing on. - </p> - <p>Note that only schedulers online can be bound to logical + process is executing on.</p> + <p>Notice that only schedulers online can be bound to logical processors.</p> - <p>For more information, see - the <c>erl</c> <seealso marker="erts:erl#+sbt">+sbt</seealso> - command line argument, + <p>For more information, see command-line argument + <seealso marker="erts:erl#+sbt">+sbt</seealso> + in <c>erl(1)</c> and <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>. </p> </item> - <tag><marker id="system_info_scheduler_id"><c>scheduler_id</c></marker></tag> + <tag><c>scheduler_id</c></tag> <item> - <p>Returns the scheduler id (<c>SchedulerId</c>) of the + <marker id="system_info_scheduler_id"></marker> + <p>Returns the scheduler ID (<c>SchedulerId</c>) of the scheduler thread that the calling process is executing - on. <c><anno>SchedulerId</anno></c> is a positive integer; where - <c><![CDATA[1 <= SchedulerId <= erlang:system_info(schedulers)]]></c>. See also + on. <c><anno>SchedulerId</anno></c> is a positive integer, + where + <c><![CDATA[1 <= SchedulerId <= erlang:system_info(schedulers)]]></c>. + See also <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>.</p> </item> - <tag><marker id="system_info_schedulers"><c>schedulers</c></marker></tag> + <tag><c>schedulers</c></tag> <item> + <marker id="system_info_schedulers"></marker> <p>Returns the number of scheduler threads used by the emulator. Scheduler threads online schedules Erlang processes and Erlang ports, and execute Erlang code - and Erlang linked in driver code.</p> + and Erlang linked-in driver code.</p> <p>The number of scheduler threads is determined at - emulator boot time and cannot be changed after - that. The amount of schedulers online can - however be changed at any time.</p> - <p>See also <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>, + emulator boot time and cannot be changed later. + However, the number of schedulers online can + be changed at any time.</p> + <p>See also + <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>, <seealso marker="#system_info_schedulers_online">erlang:system_info(schedulers_online)</seealso>, <seealso marker="#system_info_scheduler_id">erlang:system_info(scheduler_id)</seealso>, <seealso marker="#system_flag_multi_scheduling">erlang:system_flag(multi_scheduling, BlockState)</seealso>, - <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, and - and <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>.</p> + <seealso marker="#system_info_multi_scheduling">erlang:system_info(multi_scheduling)</seealso>, + and + <seealso marker="#system_info_multi_scheduling_blockers">erlang:system_info(multi_scheduling_blockers)</seealso>.</p> </item> - <tag><marker id="system_info_schedulers_online"><c>schedulers_online</c></marker></tag> + <tag><c>schedulers_online</c></tag> <item> - <p>Returns the amount of schedulers online. The scheduler - identifiers of schedulers online satisfy the following - relationship: - <c><![CDATA[1 <= SchedulerId <= erlang:system_info(schedulers_online)]]></c>. - </p> + <marker id="system_info_schedulers_online"></marker> + <p>Returns the number of schedulers online. The scheduler + identifiers of schedulers online satisfy the relationship + <c><![CDATA[1 <= SchedulerId <= erlang:system_info(schedulers_online)]]></c>.</p> <p>For more information, see - <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>, + <seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso> and - <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>. - </p> <name name="system_info" arity="1" clause_i="49"/> - + <seealso marker="#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>.</p> </item> <tag><c>smp_support</c></tag> <item> <p>Returns <c>true</c> if the emulator has been compiled - with smp support; otherwise, <c>false</c>.</p> - </item> + with SMP support, otherwise <c>false</c> is returned.</p> + </item> + <tag><marker id="system_info_start_time"/><c>start_time</c></tag> + <item><p>The <seealso marker="#monotonic_time/0">Erlang monotonic + time</seealso> in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso> at the + time when current Erlang runtime system instance started. See also + <seealso marker="#system_info_end_time"><c>erlang:system_info(end_time)</c></seealso>. + </p></item> <tag><c>system_version</c></tag> <item> <p>Returns a string containing version number and - some important properties such as the number of schedulers.</p> + some important properties, such as the number of schedulers.</p> </item> <tag><c>system_architecture</c></tag> <item> @@ -6056,102 +7411,168 @@ ok <tag><c>threads</c></tag> <item> <p>Returns <c>true</c> if the emulator has been compiled - with thread support; otherwise, <c>false</c> is - returned.</p> + with thread support, otherwise <c>false</c> is returned.</p> </item> - <tag><marker id="system_info_thread_pool_size"><c>thread_pool_size</c></marker></tag> + <tag><c>thread_pool_size</c></tag> <item> + <marker id="system_info_thread_pool_size"></marker> <p>Returns the number of async threads in the async thread pool used for asynchronous driver calls - (<seealso marker="erts:erl_driver#driver_async">driver_async()</seealso>) - as an integer.</p> + (<seealso marker="erts:erl_driver#driver_async">driver_async()</seealso>). + The value is given as an integer.</p> + </item> + + <tag><c>time_correction</c></tag> + <item> + <marker id="system_info_time_correction"></marker> + <p>Returns a boolean value indicating whether + <seealso marker="time_correction#Time_Correction">time correction</seealso> + is enabled or not. + </p></item> + <tag><c>time_offset</c></tag> + <item> + <marker id="system_info_time_offset"></marker> + <p>Returns the state of the time offset:</p> + <taglist> + <tag><c>preliminary</c></tag> + <item><p>The time offset is preliminary, and will be changed + at a later time when being finalized. The preliminary time offset + is used during the preliminary phase of the + <seealso marker="time_correction#Single_Time_Warp_Mode">single + time warp mode</seealso>.</p></item> + + <tag><c>final</c></tag> + <item><p>The time offset is final. This either because + <seealso marker="time_correction#No_Time_Warp_Mode">no + time warp mode</seealso> is used, or because the time + offset have been finalized when + <seealso marker="time_correction#Single_Time_Warp_Mode">single + time warp mode</seealso> is used.</p></item> + + <tag><c>volatile</c></tag> + <item><p>The time offset is volatile. That is, it can + change at any time. This is because + <seealso marker="time_correction#Multi_Time_Warp_Mode">multi + time warp mode</seealso> is used.</p></item> + </taglist> + </item> + <tag><marker id="system_info_time_warp_mode"/><c>time_warp_mode</c></tag> + <item><p>Returns a value identifying the + <seealso marker="time_correction#Time_Warp_Modes">time warp + mode</seealso> being used:</p> + <taglist> + <tag><c>no_time_warp</c></tag> + <item><p>The <seealso marker="time_correction#No_Time_Warp_Mode">no + time warp mode</seealso> is used.</p></item> + + <tag><c>single_time_warp</c></tag> + <item><p>The <seealso marker="time_correction#Single_Time_Warp_Mode">single + time warp mode</seealso> is used.</p></item> + + <tag><c>multi_time_warp</c></tag> + <item><p>The <seealso marker="time_correction#Multi_Time_Warp_Mode">multi + time warp mode</seealso> is used.</p></item> + </taglist> + </item> + <tag><c>tolerant_timeofday</c></tag> + <item> + <marker id="system_info_tolerant_timeofday"></marker> + <p>Returns whether a pre erts-7.0 backwards compatible compensation + for sudden changes of system time is <c>enabled</c> or <c>disabled</c>. + Such compensation is <c>enabled</c> when the + <seealso marker="#system_info_time_offset">time offset</seealso> is + <c>final</c>, and + <seealso marker="#system_info_time_correction">time correction</seealso> + is enabled.</p> </item> <tag><c>trace_control_word</c></tag> <item> - <p>Returns the value of the node's trace control word. - For more information see documentation of the function - <c>get_tcw</c> in "Match Specifications in Erlang", - <seealso marker="erts:match_spec#get_tcw">ERTS User's Guide</seealso>.</p> + <p>Returns the value of the node trace control word. For + more information, see function <c>get_tcw</c> in Section + <seealso marker="erts:match_spec#get_tcw">Match Specifications in Erlang</seealso> in the User's Guide.</p> </item> - <tag><marker id="update_cpu_info"><c>update_cpu_info</c></marker></tag> + <tag><c>update_cpu_info</c></tag> <item> - <p>The runtime system rereads the CPU information available and - updates its internally stored information about the - <seealso marker="#system_info_cpu_topology_detected">detected CPU - topology</seealso> and the amount of logical processors + <marker id="update_cpu_info"></marker> + <p>The runtime system rereads the CPU information available + and updates its internally stored information about the + <seealso marker="#system_info_cpu_topology_detected">detected + CPU topology</seealso> and the number of logical processors <seealso marker="#logical_processors">configured</seealso>, <seealso marker="#logical_processors_online">online</seealso>, and - <seealso marker="#logical_processors_available">available</seealso>. - If the CPU information has changed since the last time it was read, - the atom <c>changed</c> is returned; otherwise, the atom - <c>unchanged</c> is returned. If the CPU information has changed + <seealso marker="#logical_processors_available">available</seealso>.</p> + <p>If the CPU information has changed since the last time + it was read, the atom <c>changed</c> is returned, otherwise + the atom <c>unchanged</c>. If the CPU information has changed, you probably want to - <seealso marker="#system_flag_schedulers_online">adjust the amount - of schedulers online</seealso>. You typically want to have as - many schedulers online as - <seealso marker="#logical_processors_available">logical processors - available</seealso>. - </p> + <seealso marker="#system_flag_schedulers_online">adjust the + number of schedulers online</seealso>. You typically want + to have as many schedulers online as + <seealso marker="#logical_processors_available">logical + processors available</seealso>.</p> </item> - <tag><marker id="system_info_version"><c>version</c></marker></tag> + <tag><c>version</c></tag> <item> + <marker id="system_info_version"></marker> <p>Returns a string containing the version number of the emulator.</p> </item> <tag><c>wordsize</c></tag> <item> - <p>Same as <c>{wordsize, internal}.</c></p> + <p>Same as <c>{wordsize, internal}</c>.</p> </item> <tag><c>{wordsize, internal}</c></tag> <item> <p>Returns the size of Erlang term words in bytes as an - integer, i.e. on a 32-bit architecture 4 is returned, - and on a pure 64-bit architecture 8 is returned. On a + integer, that is, 4 is returned on a 32-bit architecture, + and 8 is returned on a pure 64-bit architecture. On a halfword 64-bit emulator, 4 is returned, as the Erlang - terms are stored using a virtual wordsize of half the - system's wordsize.</p> + terms are stored using a virtual word size of half the + system word size.</p> </item> <tag><c>{wordsize, external}</c></tag> <item> - <p>Returns the true wordsize of the emulator, i.e. the size - of a pointer, in bytes as an integer. On a pure 32-bit - architecture 4 is returned, on both a halfword and pure + <p>Returns the true word size of the emulator, that is, + the size of a pointer. The value is given in bytes + as an integer. On a pure 32-bit architecture, 4 is + returned. On both a half word and on a pure 64-bit architecture, 8 is returned.</p> </item> </taglist> <note> - <p>The <c>scheduler</c> argument has changed name to - <c>scheduler_id</c>. This in order to avoid mixup with - the <c>schedulers</c> argument. The <c>scheduler</c> - argument was introduced in ERTS version 5.5 and renamed - in ERTS version 5.5.1.</p> + <p>Argument <c>scheduler</c> has changed name to + <c>scheduler_id</c> to avoid mix up with argument + <c>schedulers</c>. Argument <c>scheduler</c> was + introduced in <c>ERTS</c> 5.5 and renamed in + <c>ERTS</c> 5.5.1.</p> </note> </desc> </func> <func> <name name="system_monitor" arity="0"/> + <fsummary>Current system performance monitoring settings.</fsummary> <type name="system_monitor_option"/> - <fsummary>Current system performance monitoring settings</fsummary> <desc> <p>Returns the current system monitoring settings set by <seealso marker="#system_monitor/2">erlang:system_monitor/2</seealso> - as <c>{<anno>MonitorPid</anno>, <anno>Options</anno>}</c>, or <c>undefined</c> if there - are no settings. The order of the options may be different + as <c>{<anno>MonitorPid</anno>, <anno>Options</anno>}</c>, + or <c>undefined</c> if there + are no settings. The order of the options can be different from the one that was set.</p> </desc> </func> <func> <name name="system_monitor" arity="1"/> + <fsummary>Sets or clears system performance monitoring options.</fsummary> <type name="system_monitor_option"/> - <fsummary>Set or clear system performance monitoring options</fsummary> <desc> - <p>When called with the argument <c>undefined</c>, all + <p>When called with argument <c>undefined</c>, all system performance monitoring settings are cleared.</p> - <p>Calling the function with <c>{<anno>MonitorPid</anno>, <anno>Options</anno>}</c> as - argument, is the same as calling - <seealso marker="#system_monitor/2">erlang:system_monitor(<anno>MonitorPid</anno>, <anno>Options</anno>)</seealso>.</p> + <p>Calling the function with <c>{<anno>MonitorPid</anno>, + <anno>Options</anno>}</c> as argument is the same as calling + <seealso marker="#system_monitor/2"><c>erlang:system_monitor(<anno>MonitorPid</anno>, <anno>Options</anno>)</c></seealso>.</p> <p>Returns the previous system monitor settings just like <seealso marker="#system_monitor/0">erlang:system_monitor/0</seealso>.</p> </desc> @@ -6159,102 +7580,101 @@ ok <func> <name name="system_monitor" arity="2"/> + <fsummary>Sets system performance monitoring options.</fsummary> <type name="system_monitor_option"/> - <fsummary>Set system performance monitoring options</fsummary> <desc> - <p>Sets system performance monitoring options. <c><anno>MonitorPid</anno></c> - is a local pid that will receive system monitor messages, and - the second argument is a list of monitoring options:</p> + <p>Sets the system performance monitoring options. + <c><anno>MonitorPid</anno></c> is a local process identifier (pid) + receiving system monitor messages. The + second argument is a list of monitoring options:</p> <taglist> <tag><c>{long_gc, Time}</c></tag> <item> <p>If a garbage collection in the system takes at least - <c>Time</c> wallclock milliseconds, a message + <c>Time</c> wall clock milliseconds, a message <c>{monitor, GcPid, long_gc, Info}</c> is sent to - <c><anno>MonitorPid</anno></c>. <c>GcPid</c> is the pid that was - garbage collected and <c>Info</c> is a list of two-element - tuples describing the result of the garbage collection. - One of the tuples is <c>{timeout, GcTime}</c> where - <c>GcTime</c> is the actual time for the garbage + <c><anno>MonitorPid</anno></c>. <c>GcPid</c> is the pid that + was garbage collected. <c>Info</c> is a list of two-element + tuples describing the result of the garbage collection.</p> + <p>One of the tuples is <c>{timeout, GcTime}</c>, where + <c>GcTime</c> is the time for the garbage collection in milliseconds. The other tuples are - tagged with <c>heap_size</c>, <c>heap_block_size</c>, - <c>stack_size</c>, <c>mbuf_size</c>, <c>old_heap_size</c>, - and <c>old_heap_block_size</c>. These tuples are - explained in the documentation of the - <seealso marker="#gc_start">gc_start</seealso> - trace message (see - <seealso marker="#trace/3">erlang:trace/3</seealso>). - New tuples may be added, and the order of the tuples in - the <c>Info</c> list may be changed at any time without prior - notice. - </p> + tagged with <c>heap_size</c>, <c>heap_block_size</c> + <c>stack_size</c>, <c>mbuf_size</c>, <c>old_heap_size</c>, + and <c>old_heap_block_size</c>. These tuples are + explained in the description of trace message + <seealso marker="#gc_start">gc_start</seealso> (see + <seealso marker="#trace/3">erlang:trace/3</seealso>). + New tuples can be added, and the order of the tuples in + the <c>Info</c> list can be changed at any time without + prior notice.</p> </item> <tag><c>{long_schedule, Time}</c></tag> <item> - <p>If a process or port in the system runs uninterrupted + <p>If a process or port in the system runs uninterrupted for at least <c>Time</c> wall clock milliseconds, a message <c>{monitor, PidOrPort, long_schedule, Info}</c> is sent to <c>MonitorPid</c>. <c>PidOrPort</c> is the - process or port that was running and <c>Info</c> is a - list of two-element tuples describing the event. In case - of a <c>pid()</c>, the tuples <c>{timeout, Millis}</c>, - <c>{in, Location}</c> and <c>{out, Location}</c> will be + process or port that was running. <c>Info</c> is a + list of two-element tuples describing the event.</p> + <p>If a <c>pid()</c>, the tuples <c>{timeout, Millis}</c>, + <c>{in, Location}</c>, and <c>{out, Location}</c> are present, where <c>Location</c> is either an MFA (<c>{Module, Function, Arity}</c>) describing the function where the process was scheduled in/out, or the - atom <c>undefined</c>. In case of a <c>port()</c>, the + atom <c>undefined</c>.</p> + <p>If a <c>port()</c>, the tuples <c>{timeout, Millis}</c> and <c>{port_op,Op}</c> - will be present. <c>Op</c> will be one of <c>proc_sig</c>, + are present. <c>Op</c> is one of <c>proc_sig</c>, <c>timeout</c>, <c>input</c>, <c>output</c>, - <c>event</c> or <c>dist_cmd</c>, depending on which - driver callback was executing. <c>proc_sig</c> is an - internal operation and should never appear, while the + <c>event</c>, or <c>dist_cmd</c>, depending on which + driver callback was executing.</p> + <p><c>proc_sig</c> is an + internal operation and is never to appear, while the others represent the corresponding driver callbacks <c>timeout</c>, <c>ready_input</c>, <c>ready_output</c>, - <c>event</c> and finally <c>outputv</c> (when the port - is used by distribution). The <c>Millis</c> value in - the <c>timeout</c> tuple will tell you the actual - uninterrupted execution time of the process or port, - which will always be <c>>=</c> the <c>Time</c> value - supplied when starting the trace. New tuples may be - added to the <c>Info</c> list in the future, and the - order of the tuples in the list may be changed at any - time without prior notice. - </p> - <p>This can be used to detect problems with NIF's or - drivers that take too long to execute. Generally, 1 ms - is considered a good maximum time for a driver callback - or a NIF. However, a time sharing system should usually - consider everything below 100 ms as "possible" and - fairly "normal". Schedule times above that might however - indicate swapping or a NIF/driver that is - misbehaving. Misbehaving NIF's and drivers could cause - bad resource utilization and bad overall performance of - the system.</p> + <c>event</c>, and <c>outputv</c> (when the port + is used by distribution). Value <c>Millis</c> in + the <c>timeout</c> tuple informs about the + uninterrupted execution time of the process or port, which + always is equal to or higher than the <c>Time</c> value + supplied when starting the trace. New tuples can be + added to the <c>Info</c> list in a future release. The + order of the tuples in the list can be changed at any + time without prior notice.</p> + <p>This can be used to detect problems with NIFs or + drivers that take too long to execute. 1 ms is + considered a good maximum time for a driver callback + or a NIF. However, a time-sharing system is usually to + consider everything below 100 ms as "possible" and + fairly "normal". However, longer schedule times can + indicate swapping or a misbehaving NIF/driver. + Misbehaving NIFs and drivers can cause bad resource + utilization and bad overall system performance.</p> </item> <tag><c>{large_heap, Size}</c></tag> <item> <p>If a garbage collection in the system results in the allocated size of a heap being at least <c>Size</c> words, a message <c>{monitor, GcPid, large_heap, Info}</c> - is sent to <c><anno>MonitorPid</anno></c>. <c>GcPid</c> and <c>Info</c> - are the same as for <c>long_gc</c> above, except that - the tuple tagged with <c>timeout</c> is not present. - <em>Note</em>: As of erts version 5.6 the monitor message - is sent if the sum of the sizes of all memory blocks allocated - for all heap generations is equal to or larger than <c>Size</c>. - Previously the monitor message was sent if the memory block - allocated for the youngest generation was equal to or larger - than <c>Size</c>. - </p> + is sent to <c><anno>MonitorPid</anno></c>. + <c>GcPid</c> and <c>Info</c> + are the same as for <c>long_gc</c> earlier, except that + the tuple tagged with <c>timeout</c> is not present.</p> + <p>As of <c>ERTS</c> 5.6, the monitor message is sent + if the sum of the sizes of all memory blocks allocated + for all heap generations is equal to or higher than <c>Size</c>. + Previously the monitor message was sent if the memory block + allocated for the youngest generation was equal to or higher + than <c>Size</c>.</p> </item> <tag><c>busy_port</c></tag> <item> <p>If a process in the system gets suspended because it sends to a busy port, a message <c>{monitor, SusPid, busy_port, Port}</c> is sent to - <c><anno>MonitorPid</anno></c>. <c>SusPid</c> is the pid that got - suspended when sending to <c>Port</c>.</p> + <c><anno>MonitorPid</anno></c>. <c>SusPid</c> is the pid + that got suspended when sending to <c>Port</c>.</p> </item> <tag><c>busy_dist_port</c></tag> <item> @@ -6262,8 +7682,8 @@ ok sends to a process on a remote node whose inter-node communication was handled by a busy port, a message <c>{monitor, SusPid, busy_dist_port, Port}</c> is sent to - <c><anno>MonitorPid</anno></c>. <c>SusPid</c> is the pid that got - suspended when sending through the inter-node + <c><anno>MonitorPid</anno></c>. <c>SusPid</c> is the pid + that got suspended when sending through the inter-node communication port <c>Port</c>.</p> </item> </taglist> @@ -6272,85 +7692,152 @@ ok <note> <p>If a monitoring process gets so large that it itself starts to cause system monitor messages when garbage - collecting, the messages will enlarge the process's + collecting, the messages enlarge the process message queue and probably make the problem worse.</p> <p>Keep the monitoring process neat and do not set the system monitor limits too tight.</p> </note> - <p>Failure: <c>badarg</c> if <c><anno>MonitorPid</anno></c> does not exist or is not a local process.</p> + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item>If <c><anno>MonitorPid</anno></c> does not exist.</item> + <tag><c>badarg</c></tag> + <item>If <c><anno>MonitorPid</anno></c> is not a local process.</item> + </taglist> </desc> </func> <func> <name name="system_profile" arity="0"/> + <fsummary>Current system profiling settings.</fsummary> <type name="system_profile_option"/> - <fsummary>Current system profiling settings</fsummary> <desc> <p>Returns the current system profiling settings set by <seealso marker="#system_profile/2">erlang:system_profile/2</seealso> - as <c>{<anno>ProfilerPid</anno>, <anno>Options</anno>}</c>, or <c>undefined</c> if there - are no settings. The order of the options may be different + as <c>{<anno>ProfilerPid</anno>, <anno>Options</anno>}</c>, + or <c>undefined</c> if there + are no settings. The order of the options can be different from the one that was set.</p> </desc> </func> <func> <name name="system_profile" arity="2"/> + <fsummary>Current system profiling settings.</fsummary> <type name="system_profile_option"/> - <fsummary>Current system profiling settings</fsummary> <desc> <p>Sets system profiler options. <c><anno>ProfilerPid</anno></c> - is a local pid or port that will receive profiling messages. The - receiver is excluded from all profiling. + is a local process identifier (pid) or port receiving profiling + messages. The receiver is excluded from all profiling. The second argument is a list of profiling options:</p> <taglist> <tag><c>exclusive</c></tag> <item> - <p> - If a synchronous call to a port from a process is done, the + <p>If a synchronous call to a port from a process is done, the calling process is considered not runnable during the call runtime to the port. The calling process is notified as - <c>inactive</c> and subsequently <c>active</c> when the port - callback returns. - </p> + <c>inactive</c>, and later <c>active</c> when the port + callback returns.</p> + </item> + <tag><c>monotonic_timestamp</c></tag> + <item> + <p>Timestamps in profile messages will use + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso>. The time-stamp (Ts) has the same + format and value as produced by + <c>erlang:monotonic_time(nano_seconds)</c>.</p> </item> <tag><c>runnable_procs</c></tag> <item> - <p>If a process is put into or removed from the run queue a message, - <c>{profile, Pid, State, Mfa, Ts}</c>, is sent to - <c><anno>ProfilerPid</anno></c>. Running processes that is reinserted into the - run queue after having been preemptively scheduled out will not trigger this - message. - </p> + <p>If a process is put into or removed from the run queue, a + message, <c>{profile, Pid, State, Mfa, Ts}</c>, is sent to + <c><anno>ProfilerPid</anno></c>. Running processes that + are reinserted into the run queue after having been + preempted do not trigger this message.</p> </item> <tag><c>runnable_ports</c></tag> <item> - <p>If a port is put into or removed from the run queue a message, - <c>{profile, Port, State, 0, Ts}</c>, is sent to - <c><anno>ProfilerPid</anno></c>. - </p> + <p>If a port is put into or removed from the run queue, a + message, <c>{profile, Port, State, 0, Ts}</c>, is sent to + <c><anno>ProfilerPid</anno></c>.</p> </item> <tag><c>scheduler</c></tag> <item> - <p>If a scheduler is put to sleep or awoken a message, - <c>{profile, scheduler, Id, State, NoScheds, Ts}</c>, is sent - to <c><anno>ProfilerPid</anno></c>. - </p> + <p>If a scheduler is put to sleep or awoken, a message, + <c>{profile, scheduler, Id, State, NoScheds, Ts}</c>, is + sent to <c><anno>ProfilerPid</anno></c>.</p> + </item> + <tag><c>strict_monotonic_timestamp</c></tag> + <item> + <p>Timestamps in profile messages will consisting of + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso> and a monotonically increasing + integer. The time-stamp (Ts) has the same format and value + as produced by <c>{erlang:monotonic_time(nano_seconds), + erlang:unique_integer([monotonic])}</c>.</p> + </item> + <tag><c>timestamp</c></tag> + <item> + <p>Timestamps in profile messages will include a + time-stamp (Ts) that has the same form as returned by + <c>erlang:now()</c>. This is also the default if no + timestamp flag is given. If <c>cpu_timestamp</c> has + been enabled via <c>erlang:trace/3</c>, this will also + effect the timestamp produced in profiling messages + when <c>timestamp</c> flag is enabled.</p> </item> </taglist> - <note><p><c>erlang:system_profile</c> is considered experimental and - its behaviour may change in the future.</p> + <note><p><c>erlang:system_profile</c> is considered experimental + and its behavior can change in a future release.</p> </note> </desc> </func> + <func> + <name name="system_time" arity="0"/> + <fsummary>Current Erlang system time</fsummary> + <desc> + <p>Returns current + <seealso marker="time_correction#Erlang_System_Time">Erlang system time</seealso> + in <c>native</c> + <seealso marker="#type_time_unit">time unit</seealso>.</p> + + <p>Calling <c>erlang:system_time()</c> is equivalent to: + <seealso marker="#monotonic_time/0"><c>erlang:monotonic_time()</c></seealso><c> + + + </c><seealso marker="#time_offset/0"><c>erlang:time_offset()</c></seealso>.</p> + <note><p>This time is <em>not</em> a monotonically increasing time + in the general case. For more information, see the documentation of + <seealso marker="time_correction#Time_Warp_Modes">time warp modes</seealso> in the + ERTS User's Guide.</p></note> + </desc> + </func> + <func> + <name name="system_time" arity="1"/> + <fsummary>Current Erlang system time</fsummary> + <desc> + <p>Returns current + <seealso marker="time_correction#Erlang_System_Time">Erlang system time</seealso> + converted into the <c><anno>Unit</anno></c> passed as argument.</p> + + <p>Calling <c>erlang:system_time(<anno>Unit</anno>)</c> is equivalent to: + <seealso marker="#convert_time_unit/3"><c>erlang:convert_time_unit</c></seealso><c>(</c><seealso marker="#system_time/0"><c>erlang:system_time()</c></seealso><c>, + native, <anno>Unit</anno>)</c>.</p> + + <note><p>This time is <em>not</em> a monotonically increasing time + in the general case. For more information, see the documentation of + <seealso marker="time_correction#Time_Warp_Modes">time warp modes</seealso> in the + ERTS User's Guide.</p></note> + </desc> + </func> <func> <name name="term_to_binary" arity="1"/> - <fsummary>Encode a term to an Erlang external term format binary</fsummary> + <fsummary>Encodes a term to an Erlang external term format binary.</fsummary> <desc> - <p>Returns a binary data object which is the result of encoding - <c><anno>Term</anno></c> according to the Erlang external term format.</p> - <p>This can be used for a variety of purposes, for example + <p>Returns a binary data object that is the result of encoding + <c><anno>Term</anno></c> according to the Erlang external + term format.</p> + <p>This can be used for various purposes, for example, writing a term to a file in an efficient way, or sending an Erlang term to some type of communications channel not supported by distributed Erlang.</p> @@ -6358,246 +7845,372 @@ ok <seealso marker="#binary_to_term/1">binary_to_term/1</seealso>.</p> </desc> </func> + <func> <name name="term_to_binary" arity="2"/> - <fsummary>Encode a term to en Erlang external term format binary</fsummary> - <desc> - <p>Returns a binary data object which is the result of encoding - <c><anno>Term</anno></c> according to the Erlang external term format.</p> - <p>If the option <c>compressed</c> is provided, the external - term format will be compressed. The compressed format is - automatically recognized by <c>binary_to_term/1</c> in R7B and later.</p> - <p>It is also possible to specify a compression level by giving - the option <c>{compressed, <anno>Level</anno>}</c>, where <c><anno>Level</anno></c> is an - integer from 0 through 9. <c>0</c> means that no compression - will be done (it is the same as not giving any <c>compressed</c> option); - <c>1</c> will take the least time but may not compress as well as - the higher levels; <c>9</c> will take the most time and may produce - a smaller result. Note the "mays" in the preceding sentence; depending - on the input term, level 9 compression may or may not produce a smaller - result than level 1 compression.</p> - <p>Currently, <c>compressed</c> gives the same result as - <c>{compressed, 6}</c>.</p> - <p>The option <c>{minor_version, <anno>Version</anno>}</c> can be use to control - some details of the encoding. This option was - introduced in R11B-4. Currently, the allowed values for <c><anno>Version</anno></c> - are <c>0</c> and <c>1</c>.</p> - <p><c>{minor_version, 1}</c> forces any floats in the term to be encoded - in a more space-efficient and exact way (namely in the 64-bit IEEE format, - rather than converted to a textual representation). <c>binary_to_term/1</c> - in R11B-4 and later is able decode the new representation.</p> - <p><c>{minor_version, 0}</c> is currently the default, meaning that floats - will be encoded using a textual representation; this option is useful if - you want to ensure that releases prior to R11B-4 can decode resulting + <fsummary>Encodes a term to en Erlang external term format binary.</fsummary> + <desc> + <p>Returns a binary data object that is the result of encoding + <c><anno>Term</anno></c> according to the Erlang external + term format.</p> + <p>If option <c>compressed</c> is provided, the external term + format is compressed. The compressed format is automatically + recognized by <c>binary_to_term/1</c> as from Erlang R7B.</p> + <p>A compression level can be specified by giving option + <c>{compressed, <anno>Level</anno>}</c>. + <c><anno>Level</anno></c> is an integer + with range 0..9, where:</p> + <list type="bulleted"> + <item><c>0</c> - No compression is done (it is the same as + giving no <c>compressed</c> option).</item> + <item><c>1</c> - Takes least time but may not compress + as well as the higher levels.</item> + <item><c>6</c> - Default level when option <c>compressed</c> + is provided.</item> + <item><c>9</c> - Takes most time and tries to produce a smaller + result. Notice "tries" in the preceding sentence; depending + on the input term, level 9 compression either does or does + not produce a smaller result than level 1 compression.</item> + </list> + <p>Option <c>{minor_version, <anno>Version</anno>}</c> + can be used to control + some encoding details. This option was introduced in OTP R11B-4. + The valid values for <c><anno>Version</anno></c> are + <c>0</c> and <c>1</c>.</p> + <p>As from OTP 17.0, <c>{minor_version, 1}</c> is the default. It + forces any floats in the term to be encoded in a more + space-efficient and exact way (namely in the 64-bit IEEE format, + rather than converted to a textual representation).</p> + <p>As from OTP R11B-4, <c>binary_to_term/1</c> can decode this + representation.</p> + <p><c>{minor_version, 0}</c> means that floats are encoded + using a textual representation. This option is useful to + ensure that releases before OTP R11B-4 can decode resulting binary.</p> <p>See also <seealso marker="#binary_to_term/1">binary_to_term/1</seealso>.</p> </desc> </func> + <func> <name name="throw" arity="1"/> - <fsummary>Throw an exception</fsummary> + <fsummary>Throws an exception.</fsummary> <desc> <p>A non-local return from a function. If evaluated within a - <c>catch</c>, <c>catch</c> will return the value <c><anno>Any</anno></c>.</p> + <c>catch</c>, <c>catch</c> returns value <c><anno>Any</anno></c>.</p> + <p>Example:</p> <pre> > <input>catch throw({hello, there}).</input> {hello,there}</pre> <p>Failure: <c>nocatch</c> if not evaluated within a catch.</p> </desc> </func> + <func> <name name="time" arity="0"/> - <fsummary>Current time</fsummary> + <fsummary>Current time.</fsummary> <desc> <p>Returns the current time as <c>{Hour, Minute, Second}</c>.</p> - <p>The time zone and daylight saving time correction depend on + <p>The time zone and Daylight Saving Time correction depend on the underlying OS.</p> + <p>Example:</p> <pre> > <input>time().</input> {9,42,44}</pre> </desc> </func> + + <func> + <name name="time_offset" arity="0"/> + <fsummary>Current time offset</fsummary> + <desc> + <p>Returns the current time offset between + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang monotonic time</seealso> + and + <seealso marker="time_correction#Erlang_System_Time">Erlang system time</seealso> in + <c>native</c> <seealso marker="#type_time_unit">time unit</seealso>. + Current time offset added to an Erlang monotonic time gives + corresponding Erlang system time.</p> + + <p>The time offset may or may not change during operation depending + on the <seealso marker="time_correction#Time_Warp_Modes">time + warp mode</seealso> used.</p> + + <note> + <p>A change in time offset may be observed at slightly + different points in time by different processes.</p> + + <p>If the runtime system is in + <seealso marker="time_correction#Multi_Time_Warp_Mode">multi + time warp mode</seealso>, the time offset will be changed when + the runtime system detects that the + <seealso marker="time_correction#OS_System_Time">OS system + time</seealso> has changed. The runtime system will, however, + not detect this immediately when it happens. A task checking + the time offset is scheduled to execute at least once a minute, + so under normal operation this should be detected within a + minute, but during heavy load it might take longer time.</p> + </note> + </desc> + </func> + <func> + <name name="time_offset" arity="1"/> + <fsummary>Current time offset</fsummary> + <desc> + <p>Returns the current time offset between + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang monotonic time</seealso> + and + <seealso marker="time_correction#Erlang_System_Time">Erlang system time</seealso> + converted into the <c><anno>Unit</anno></c> passed as argument.</p> + + <p>Same as calling + <seealso marker="#convert_time_unit/3"><c>erlang:convert_time_unit</c></seealso><c>(</c><seealso marker="#time_offset/0"><c>erlang:time_offset()</c></seealso><c>, native, <anno>Unit</anno>)</c> + however optimized for commonly used <c><anno>Unit</anno></c>s.</p> + </desc> + </func> + <func> + <name name="timestamp" arity="0"/> + <fsummary>Current Erlang System time</fsummary> + <type name="timestamp"/> + <desc> + <p>Returns current + <seealso marker="time_correction#Erlang_System_Time">Erlang system time</seealso> + on the format <c>{MegaSecs, Secs, MicroSecs}</c>. This format is + the same as <seealso marker="kernel:os#timestamp/0"><c>os:timestamp/0</c></seealso> + and the deprecated <seealso marker="#now/0"><c>erlang:now/0</c></seealso> + uses. The reason for the existence of <c>erlang:timestamp()</c> is + purely to simplify usage for existing code that assumes this timestamp + format. Current Erlang system time can more efficiently be retrieved in + the time unit of your choice using + <seealso marker="#system_time/1"><c>erlang:system_time/1</c></seealso>.</p> + + <p>The <c>erlang:timestamp()</c> BIF is equivalent to:</p><code type="none"> +timestamp() -> + ErlangSystemTime = erlang:system_time(micro_seconds), + MegaSecs = ErlangSystemTime div 1000000000000, + Secs = ErlangSystemTime div 1000000 - MegaSecs*1000000, + MicroSecs = ErlangSystemTime rem 1000000, + {MegaSecs, Secs, MicroSecs}.</code> + <p>It, however, uses a native implementation which does + not build garbage on the heap and with slightly better + performance.</p> + + <note><p>This time is <em>not</em> a monotonically increasing time + in the general case. For more information, see the documentation of + <seealso marker="time_correction#Time_Warp_Modes">time warp modes</seealso> in the + ERTS User's Guide.</p></note> + </desc> + + </func> <func> <name name="tl" arity="1"/> - <fsummary>Tail of a list</fsummary> + <fsummary>Tail of a list.</fsummary> <desc> - <p>Returns the tail of <c><anno>List</anno></c>, that is, the list minus - the first element.</p> + <p>Returns the tail of <c><anno>List</anno></c>, that is, + the list minus the first element, for example:</p> <pre> > <input>tl([geesties, guilies, beasties]).</input> [guilies, beasties]</pre> <p>Allowed in guard tests.</p> - <p>Failure: <c>badarg</c> if <c><anno>List</anno></c> is the empty list [].</p> + <p>Failure: <c>badarg</c> if <c><anno>List</anno></c> + is the empty list <c>[]</c>.</p> </desc> </func> + <func> <name name="trace" arity="3"/> + <fsummary>Sets trace flags for a process or processes.</fsummary> <type name="trace_flag"/> - <fsummary>Set trace flags for a process or processes</fsummary> <desc> <p>Turns on (if <c><anno>How</anno> == true</c>) or off (if - <c><anno>How</anno> == false</c>) the trace flags in <c><anno>FlagList</anno></c> for - the process or processes represented by <c><anno>PidSpec</anno></c>.</p> - <p><c><anno>PidSpec</anno></c> is either a pid for a local process, or one of - the following atoms:</p> + <c><anno>How</anno> == false</c>) the trace flags in + <c><anno>FlagList</anno></c> for + the process or processes represented by + <c><anno>PidSpec</anno></c>.</p> + <p><c><anno>PidSpec</anno></c> is either a process identifier + (pid) for a local process, or one of the following atoms:</p> <taglist> <tag><c>existing</c></tag> <item> - <p>All processes currently existing.</p> + <p>All currently existing processes.</p> </item> <tag><c>new</c></tag> <item> - <p>All processes that will be created in the future.</p> + <p>All processes that are created in the future.</p> </item> <tag><c>all</c></tag> <item> <p>All currently existing processes and all processes that - will be created in the future.</p> + are created in the future.</p> </item> </taglist> - <p><c><anno>FlagList</anno></c> can contain any number of the following - flags (the "message tags" refers to the list of messages - following below):</p> + <p><c><anno>FlagList</anno></c> can contain any number of the + following flags (the "message tags" refers to the list of + <seealso marker="#trace_3_trace_messages">trace messages</seealso>):</p> <taglist> <tag><c>all</c></tag> <item> - <p>Set all trace flags except <c>{tracer, Tracer}</c> and - <c>cpu_timestamp</c> that are in their nature different + <p>Sets all trace flags except <c>{tracer, Tracer}</c> and + <c>cpu_timestamp</c>, which are in their nature different than the others.</p> </item> <tag><c>send</c></tag> <item> - <p>Trace sending of messages.</p> - <p>Message tags: <c>send</c>, + <p>Traces sending of messages.</p> + <p>Message tags: <c>send</c> and <c>send_to_non_existing_process</c>.</p> </item> <tag><c>'receive'</c></tag> <item> - <p>Trace receiving of messages.</p> + <p>Traces receiving of messages.</p> <p>Message tags: <c>'receive'</c>.</p> </item> <tag><c>procs</c></tag> <item> - <p>Trace process related events.</p> + <p>Traces process-related events.</p> <p>Message tags: <c>spawn</c>, <c>exit</c>, <c>register</c>, <c>unregister</c>, <c>link</c>, - <c>unlink</c>, <c>getting_linked</c>, + <c>unlink</c>, <c>getting_linked</c>, and <c>getting_unlinked</c>.</p> </item> <tag><c>call</c></tag> <item> - <p>Trace certain function calls. Specify which function + <p>Traces certain function calls. Specify which function calls to trace by calling <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p> - <p>Message tags: <c>call</c>, <c>return_from</c>.</p> + <p>Message tags: <c>call</c> and <c>return_from</c>.</p> </item> <tag><c>silent</c></tag> <item> - <p>Used in conjunction with the <c>call</c> trace flag. - The <c>call</c>, <c>return_from</c> and <c>return_to</c> - trace messages are inhibited if this flag is set, - but if there are match specs they are executed as normal.</p> + <p>Used with the <c>call</c> trace flag. + The <c>call</c>, <c>return_from</c>, and <c>return_to</c> + trace messages are inhibited if this flag is set, but they + are executed as normal if there are match specifications.</p> <p>Silent mode is inhibited by executing <c>erlang:trace(_, false, [silent|_])</c>, - or by a match spec executing the <c>{silent, false}</c> - function.</p> + or by a match specification executing the function + <c>{silent, false}</c>.</p> <p>The <c>silent</c> trace flag facilitates setting up a trace on many or even all processes in the system. - Then the interesting trace can be activated and - deactivated using the <c>{silent,Bool}</c> - match spec function, giving a high degree - of control of which functions with which - arguments that triggers the trace.</p> - <p>Message tags: <c>call</c>, <c>return_from</c>, + The trace can then be activated and deactivated using the match + specification function <c>{silent,Bool}</c>, giving + a high degree of control of which functions with which + arguments that trigger the trace.</p> + <p>Message tags: <c>call</c>, <c>return_from</c>, and <c>return_to</c>. Or rather, the absence of.</p> </item> <tag><c>return_to</c></tag> <item> - <p>Used in conjunction with the <c>call</c> trace flag. - Trace the actual return from a traced function back to + <p>Used with the <c>call</c> trace flag. + Traces the return from a traced function back to its caller. Only works for functions traced with - the <c>local</c> option to + option <c>local</c> to <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p> <p>The semantics is that a trace message is sent when a - call traced function actually returns, that is, when a - chain of tail recursive calls is ended. There will be - only one trace message sent per chain of tail recursive - calls, why the properties of tail recursiveness for + call traced function returns, that is, when a + chain of tail recursive calls ends. Only one trace + message is sent per chain of tail recursive calls, + so the properties of tail recursiveness for function calls are kept while tracing with this flag. Using <c>call</c> and <c>return_to</c> trace together makes it possible to know exactly in which function a process executes at any time.</p> <p>To get trace messages containing return values from - functions, use the <c>{return_trace}</c> match_spec - action instead.</p> + functions, use the <c>{return_trace}</c> match + specification action instead.</p> <p>Message tags: <c>return_to</c>.</p> </item> <tag><c>running</c></tag> <item> - <p>Trace scheduling of processes.</p> - <p>Message tags: <c>in</c>, and <c>out</c>.</p> + <p>Traces scheduling of processes.</p> + <p>Message tags: <c>in</c> and <c>out</c>.</p> </item> <tag><c>exiting</c></tag> <item> - <p>Trace scheduling of an exiting processes.</p> + <p>Traces scheduling of exiting processes.</p> <p>Message tags: <c>in_exiting</c>, <c>out_exiting</c>, and <c>out_exited</c>.</p> </item> <tag><c>garbage_collection</c></tag> <item> - <p>Trace garbage collections of processes.</p> - <p>Message tags: <c>gc_start</c>, <c>gc_end</c>.</p> + <p>Traces garbage collections of processes.</p> + <p>Message tags: <c>gc_start</c> and <c>gc_end</c>.</p> </item> <tag><c>timestamp</c></tag> <item> - <p>Include a time stamp in all trace messages. The time - stamp (Ts) is of the same form as returned by + <p>Includes a time-stamp in all trace messages. The + time-stamp (Ts) has the same form as returned by <c>erlang:now()</c>.</p> </item> <tag><c>cpu_timestamp</c></tag> <item> <p>A global trace flag for the Erlang node that makes all - trace timestamps be in CPU time, not wallclock. It is - only allowed with <c>PidSpec==all</c>. If the host - machine operating system does not support high resolution + trace time-stamps using the <c>timestamp</c> flag to be + in CPU time, not wall clock time. That is, <c>cpu_timestamp</c> + will not be used if <c>monotonic_timestamp</c>, or + <c>strict_monotonic_timestamp</c> is enabled. + Only allowed with <c>PidSpec==all</c>. If the host + machine OS does not support high-resolution CPU time measurements, <c>trace/3</c> exits with - <c>badarg</c>.</p> + <c>badarg</c>. Notice that most OS do + not synchronize this value across cores, so be prepared + that time might seem to go backwards when using this option.</p> + </item> + <tag><c>monotonic_timestamp</c></tag> + <item> + <p>Includes an + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso> time-stamp in all trace messages. The + time-stamp (Ts) has the same format and value as produced by + <c>erlang:monotonic_time(nano_seconds)</c>. This flag overrides + the <c>cpu_timestamp</c> flag.</p> + </item> + <tag><c>strict_monotonic_timestamp</c></tag> + <item> + <p>Includes an timestamp consisting of + <seealso marker="time_correction#Erlang_Monotonic_Time">Erlang + monotonic time</seealso> and a monotonically increasing + integer in all trace messages. The time-stamp (Ts) has the + same format and value as produced by + <c>{erlang:monotonic_time(nano_seconds), + erlang:unique_integer([monotonic])}</c>. This flag overrides + the <c>cpu_timestamp</c> flag.</p> </item> <tag><c>arity</c></tag> <item> - <p>Used in conjunction with the <c>call</c> trace flag. - <c>{M, F, Arity}</c> will be specified instead of + <p>Used with the <c>call</c> trace flag. + <c>{M, F, Arity}</c> is specified instead of <c>{M, F, Args}</c> in call trace messages.</p> </item> <tag><c>set_on_spawn</c></tag> <item> <p>Makes any process created by a traced process inherit - its trace flags, including the <c>set_on_spawn</c> flag.</p> + its trace flags, including flag <c>set_on_spawn</c>.</p> </item> <tag><c>set_on_first_spawn</c></tag> <item> <p>Makes the first process created by a traced process - inherit its trace flags, excluding - the <c>set_on_first_spawn</c> flag.</p> + inherit its trace flags, excluding flag + <c>set_on_first_spawn</c>.</p> </item> <tag><c>set_on_link</c></tag> <item> <p>Makes any process linked by a traced process inherit its - trace flags, including the <c>set_on_link</c> flag.</p> + trace flags, including flag <c>set_on_link</c>.</p> </item> <tag><c>set_on_first_link</c></tag> <item> <p>Makes the first process linked to by a traced process - inherit its trace flags, excluding - the <c>set_on_first_link</c> flag.</p> + inherit its trace flags, excluding flag + <c>set_on_first_link</c>.</p> </item> <tag><c>{tracer, Tracer}</c></tag> <item> - <p>Specify where to send the trace messages. <c>Tracer</c> - must be the pid of a local process or the port identifier + <p>Specifies where to send the trace messages. <c>Tracer</c> + must be the process identifier of a local process + or the port identifier of a local port. If this flag is not given, trace - messages will be sent to the process that called + messages are sent to the process that called <c>erlang:trace/3</c>.</p> </item> </taglist> @@ -6605,27 +8218,34 @@ ok <c>set_on_link</c> is the same as having <c>set_on_first_link</c> alone. Likewise for <c>set_on_spawn</c> and <c>set_on_first_spawn</c>.</p> - <p>If the <c>timestamp</c> flag is not given, the tracing - process will receive the trace messages described below. - <c>Pid</c> is the pid of the traced process in which - the traced event has occurred. The third element of the tuple - is the message tag.</p> - <p>If the <c>timestamp</c> flag is given, the first element of - the tuple will be <c>trace_ts</c> instead and the timestamp - is added last in the tuple.</p> + <p>The tracing process receives the <em>trace messages</em> described + in the following list. <c>Pid</c> is the process identifier of the + traced process in which the traced event has occurred. The + third tuple element is the message tag.</p> + <p>If flag <c>timestamp</c>, <c>strict_monotonic_timestamp</c>, or + <c>monotonic_timestamp</c> is given, the first tuple + element is <c>trace_ts</c> instead, and the time-stamp + is added as an extra element last in the message tuple. If + multiple timestamp flags are passed, <c>timestamp</c> has + precedence over <c>strict_monotonic_timestamp</c> which + in turn has precedence over <c>monotonic_timestamp</c>. All + timestamp flags are remembered, so if two are passed + and the one with highest precedence later is disabled + the other one will become active.</p> + <marker id="trace_3_trace_messages"></marker> <taglist> <tag><c>{trace, Pid, 'receive', Msg}</c></tag> <item> - <p>When <c>Pid</c> receives the message <c>Msg</c>.</p> + <p>When <c>Pid</c> receives message <c>Msg</c>.</p> </item> <tag><c>{trace, Pid, send, Msg, To}</c></tag> <item> - <p>When <c>Pid</c> sends the message <c>Msg</c> to - the process <c>To</c>.</p> + <p>When <c>Pid</c> sends message <c>Msg</c> to + process <c>To</c>.</p> </item> <tag><c>{trace, Pid, send_to_non_existing_process, Msg, To}</c></tag> <item> - <p>When <c>Pid</c> sends the message <c>Msg</c> to + <p>When <c>Pid</c> sends message <c>Msg</c> to the non-existing process <c>To</c>.</p> </item> <tag><c>{trace, Pid, call, {M, F, Args}}</c></tag> @@ -6633,7 +8253,7 @@ ok <p>When <c>Pid</c> calls a traced function. The return values of calls are never supplied, only the call and its arguments.</p> - <p>Note that the trace flag <c>arity</c> can be used to + <p>Trace flag <c>arity</c> can be used to change the contents of this message, so that <c>Arity</c> is specified instead of <c>Args</c>.</p> </item> @@ -6641,35 +8261,34 @@ ok <item> <p>When <c>Pid</c> returns <em>to</em> the specified function. This trace message is sent if both - the <c>call</c> and the <c>return_to</c> flags are set, + the flags <c>call</c> and <c>return_to</c> are set, and the function is set to be traced on <em>local</em> function calls. The message is only sent when returning - from a chain of tail recursive function calls where at + from a chain of tail recursive function calls, where at least one call generated a <c>call</c> trace message - (that is, the functions match specification matched and + (that is, the functions match specification matched, and <c>{message, false}</c> was not an action).</p> </item> <tag><c>{trace, Pid, return_from, {M, F, Arity}, ReturnValue}</c></tag> <item> <p>When <c>Pid</c> returns <em>from</em> the specified - function. This trace message is sent if the <c>call</c> - flag is set, and the function has a match specification + function. This trace message is sent if flag <c>call</c> + is set, and the function has a match specification with a <c>return_trace</c> or <c>exception_trace</c> action.</p> </item> <tag><c>{trace, Pid, exception_from, {M, F, Arity}, {Class, Value}}</c></tag> <item> <p>When <c>Pid</c> exits <em>from</em> the specified - function due to an exception. This trace message is sent - if the <c>call</c> flag is set, and the function has + function because of an exception. This trace message is + sent if flag <c>call</c> is set, and the function has a match specification with an <c>exception_trace</c> action.</p> </item> <tag><c>{trace, Pid, spawn, Pid2, {M, F, Args}}</c></tag> <item> <p>When <c>Pid</c> spawns a new process <c>Pid2</c> with the specified function call as entry point.</p> - <p>Note that <c>Args</c> is supposed to be the argument - list, but may be any term in the case of an erroneous - spawn.</p> + <p><c>Args</c> is supposed to be the argument list, + but can be any term if the spawn is erroneous.</p> </item> <tag><c>{trace, Pid, exit, Reason}</c></tag> <item> @@ -6699,148 +8318,158 @@ ok <tag><c>{trace, Pid, unregister, RegName}</c></tag> <item> <p>When <c>Pid</c> gets the name <c>RegName</c> unregistered. - Note that this is done automatically when a registered + This is done automatically when a registered process exits.</p> </item> <tag><c>{trace, Pid, in, {M, F, Arity} | 0}</c></tag> <item> - <p>When <c>Pid</c> is scheduled to run. The process will - run in function <c>{M, F, Arity}</c>. On some rare - occasions the current function cannot be determined, then - the last element <c>Arity</c> is 0.</p> + <p>When <c>Pid</c> is scheduled to run. The process + runs in function <c>{M, F, Arity}</c>. On some rare + occasions, the current function cannot be determined, + then the last element is <c>0</c>.</p> </item> <tag><c>{trace, Pid, out, {M, F, Arity} | 0}</c></tag> <item> <p>When <c>Pid</c> is scheduled out. The process was - running in function {M, F, Arity}. On some rare occasions + running in function {M, F, Arity}. On some rare occasions, the current function cannot be determined, then the last - element <c>Arity</c> is 0.</p> + element is <c>0</c>.</p> </item> - <tag><marker id="gc_start"><c>{trace, Pid, gc_start, Info}</c></marker></tag> + <tag><c>{trace, Pid, gc_start, Info}</c></tag> <item> + <marker id="gc_start"></marker> <p>Sent when garbage collection is about to be started. <c>Info</c> is a list of two-element tuples, where the first element is a key, and the second is the value. - You should not depend on the tuples have any defined - order. Currently, the following keys are defined:</p> + Do not depend on any order of the tuples. + The following keys are defined:</p> <taglist> <tag><c>heap_size</c></tag> <item>The size of the used part of the heap.</item> <tag><c>heap_block_size</c></tag> <item>The size of the memory block used for storing - the heap and the stack.</item> + the heap and the stack.</item> <tag><c>old_heap_size</c></tag> <item>The size of the used part of the old heap.</item> <tag><c>old_heap_block_size</c></tag> <item>The size of the memory block used for storing - the old heap.</item> + the old heap.</item> <tag><c>stack_size</c></tag> - <item>The actual size of the stack.</item> + <item>The size of the stack.</item> <tag><c>recent_size</c></tag> <item>The size of the data that survived the previous garbage - collection.</item> + collection.</item> <tag><c>mbuf_size</c></tag> <item>The combined size of message buffers associated with - the process.</item> - + the process.</item> <tag><c>bin_vheap_size</c></tag> - <item>The total size of unique off-heap binaries referenced from the process heap.</item> + <item>The total size of unique off-heap binaries referenced + from the process heap.</item> <tag><c>bin_vheap_block_size</c></tag> - <item>The total size of binaries, in words, allowed in the virtual - heap in the process before doing a garbage collection. </item> + <item>The total size of binaries allowed in the virtual + heap in the process before doing a garbage collection.</item> <tag><c>bin_old_vheap_size</c></tag> - <item>The total size of unique off-heap binaries referenced from the process old heap.</item> - <tag><c>bin_vheap_block_size</c></tag> - <item>The total size of binaries, in words, allowed in the virtual - old heap in the process before doing a garbage collection. </item> - - + <item>The total size of unique off-heap binaries referenced + from the process old heap.</item> + <tag><c>bin_old_vheap_block_size</c></tag> + <item>The total size of binaries allowed in the virtual + old heap in the process before doing a garbage collection.</item> </taglist> <p>All sizes are in words.</p> </item> <tag><c>{trace, Pid, gc_end, Info}</c></tag> <item> <p>Sent when garbage collection is finished. <c>Info</c> - contains the same kind of list as in the <c>gc_start</c> - message, but the sizes reflect the new sizes after + contains the same kind of list as in message <c>gc_start</c>, + but the sizes reflect the new sizes after garbage collection.</p> </item> </taglist> - <p>If the tracing process dies, the flags will be silently + <p>If the tracing process dies, the flags are silently removed.</p> - <p>Only one process can trace a particular process. For this - reason, attempts to trace an already traced process will fail.</p> + <p>Only one process can trace a particular process. Therefore, + attempts to trace an already traced process fail.</p> <p>Returns: A number indicating the number of processes that - matched <c><anno>PidSpec</anno></c>. If <c><anno>PidSpec</anno></c> is a pid, - the return value will be <c>1</c>. If <c><anno>PidSpec</anno></c> is - <c>all</c> or <c>existing</c> the return value will be + matched <c><anno>PidSpec</anno></c>. + If <c><anno>PidSpec</anno></c> is a process + identifier, the return value is <c>1</c>. + If <c><anno>PidSpec</anno></c> + is <c>all</c> or <c>existing</c>, the return value is the number of processes running, excluding tracer processes. - If <c><anno>PidSpec</anno></c> is <c>new</c>, the return value will be + If <c><anno>PidSpec</anno></c> is <c>new</c>, the return value is <c>0</c>.</p> - <p>Failure: If specified arguments are not supported. For - example <c>cpu_timestamp</c> is not supported on all - platforms.</p> + <p>Failure: <c>badarg</c> if the specified arguments are + not supported. For example, <c>cpu_timestamp</c> is not + supported on all platforms.</p> </desc> </func> + <func> <name name="trace_delivered" arity="1"/> - <fsummary>Notification when trace has been delivered</fsummary> + <fsummary>Notification when trace has been delivered.</fsummary> <desc> <p>The delivery of trace messages is dislocated on the time-line - compared to other events in the system. If you know that the - <c><anno>Tracee</anno></c> has passed some specific point in its execution, + compared to other events in the system. If you know that + <c><anno>Tracee</anno></c> has passed some specific point + in its execution, and you want to know when at least all trace messages - corresponding to events up to this point have reached the tracer - you can use <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>. A + corresponding to events up to this point have reached the + tracer, use <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>. A <c>{trace_delivered, <anno>Tracee</anno>, <anno>Ref</anno>}</c> message is sent to the caller of <c>erlang:trace_delivered(<anno>Tracee</anno>)</c> when it - is guaranteed that all trace messages have been delivered to - the tracer up to the point that the <c><anno>Tracee</anno></c> had reached + is guaranteed that all trace messages are delivered to + the tracer up to the point that <c><anno>Tracee</anno></c> reached at the time of the call to <c>erlang:trace_delivered(<anno>Tracee</anno>)</c>.</p> - <p>Note that the <c>trace_delivered</c> message does <em>not</em> - imply that trace messages have been delivered; instead, it implies - that all trace messages that <em>should</em> be delivered have - been delivered. It is not an error if <c><anno>Tracee</anno></c> isn't, and - hasn't been traced by someone, but if this is the case, - <em>no</em> trace messages will have been delivered when the + <p>Notice that message <c>trace_delivered</c> does <em>not</em> + imply that trace messages have been delivered. + Instead it implies that all trace messages that + <em>are to be delivered</em> have been delivered. + It is not an error if <c><anno>Tracee</anno></c> is not, and + has not been traced by someone, but if this is the case, + <em>no</em> trace messages have been delivered when the <c>trace_delivered</c> message arrives.</p> - <p>Note that <c><anno>Tracee</anno></c> has to refer to a process currently, + <p>Notice that that <c><anno>Tracee</anno></c> must refer + to a process currently, or previously existing on the same node as the caller of <c>erlang:trace_delivered(<anno>Tracee</anno>)</c> resides on. - The special <c><anno>Tracee</anno></c> atom <c>all</c> denotes all processes + The special <c><anno>Tracee</anno></c> atom <c>all</c> + denotes all processes that currently are traced in the node.</p> - <p>An example: Process <c>A</c> is <c><anno>Tracee</anno></c>, port <c>B</c> is - tracer, and process <c>C</c> is the port owner of <c>B</c>. - <c>C</c> wants to close <c>B</c> when <c>A</c> exits. <c>C</c> - can ensure that the trace isn't truncated by calling - <c>erlang:trace_delivered(A)</c> when <c>A</c> exits and wait - for the <c>{trace_delivered, A, <anno>Ref</anno>}</c> message before closing - <c>B</c>.</p> - <p>Failure: <c>badarg</c> if <c><anno>Tracee</anno></c> does not refer to a + <p>Example: Process <c>A</c> is <c><anno>Tracee</anno></c>, + port <c>B</c> is tracer, and process <c>C</c> is the port + owner of <c>B</c>. <c>C</c> wants to close <c>B</c> when + <c>A</c> exits. To ensure that the trace is not truncated, + <c>C</c> can call <c>erlang:trace_delivered(A)</c>, when + <c>A</c> exits, and wait for message <c>{trace_delivered, A, + <anno>Ref</anno>}</c> before closing <c>B</c>.</p> + <p>Failure: <c>badarg</c> if <c><anno>Tracee</anno></c> + does not refer to a process (dead or alive) on the same node as the caller of <c>erlang:trace_delivered(<anno>Tracee</anno>)</c> resides on.</p> </desc> </func> + <func> <name name="trace_info" arity="2"/> + <fsummary>Trace information about a process or function.</fsummary> <type name="trace_info_return"/> <type name="trace_info_item_result"/> <type name="trace_info_flag"/> <type name="trace_match_spec"/> - <fsummary>Trace information about a process or function</fsummary> <desc> <p>Returns trace information about a process or function.</p> - <p>To get information about a process, <c><anno>PidOrFunc</anno></c> should - be a pid or the atom <c>new</c>. The atom <c>new</c> means - that the default trace state for processes to be created will - be returned. <c><anno>Item</anno></c> must have one of the following - values:</p> + <p>To get information about a process, + <c><anno>PidOrFunc</anno></c> is to + be a process identifier (pid) or the atom <c>new</c>. + The atom <c>new</c> means that the default trace state for + processes to be created is returned.</p> + <p>The following <c>Item</c>s are valid:</p> <taglist> <tag><c>flags</c></tag> <item> - <p>Return a list of atoms indicating what kind of traces is - enabled for the process. The list will be empty if no + <p>Returns a list of atoms indicating what kind of traces is + enabled for the process. The list is empty if no traces are enabled, and one or more of the followings atoms if traces are enabled: <c>send</c>, <c>'receive'</c>, <c>set_on_spawn</c>, <c>call</c>, @@ -6851,358 +8480,474 @@ ok </item> <tag><c>tracer</c></tag> <item> - <p>Return the identifier for process or port tracing this + <p>Returns the identifier for process or port tracing this process. If this process is not being traced, the return - value will be <c>[]</c>.</p> + value is <c>[]</c>.</p> </item> </taglist> - <p>To get information about a function, <c>PidOrFunc</c> should - be a three-element tuple: <c>{Module, Function, Arity}</c> or - the atom <c>on_load</c>. No wildcards are allowed. Returns - <c>undefined</c> if the function does not exist or - <c>false</c> if the function is not traced at all. <c>Item</c> - must have one of the following values:</p> + <p>To get information about a function, <c>PidOrFunc</c> is to + be the three-element tuple <c>{Module, Function, Arity}</c> or + the atom <c>on_load</c>. No wild cards are allowed. Returns + <c>undefined</c> if the function does not exist, or + <c>false</c> if the function is not traced.</p> + <p>The following <c>Item</c>s are valid::</p> <taglist> <tag><c>traced</c></tag> <item> - <p>Return <c>global</c> if this function is traced on + <p>Returns <c>global</c> if this function is traced on global function calls, <c>local</c> if this function is - traced on local function calls (i.e local and global - function calls), and <c>false</c> if neither local nor - global function calls are traced.</p> + traced on local function calls (that is, local and global + function calls), and <c>false</c> if local or + global function calls are not traced.</p> </item> <tag><c>match_spec</c></tag> <item> - <p>Return the match specification for this function, if it + <p>Returns the match specification for this function, if it has one. If the function is locally or globally traced but has no match specification defined, the returned value is <c>[]</c>.</p> </item> <tag><c>meta</c></tag> <item> - <p>Return the meta trace tracer process or port for this - function, if it has one. If the function is not meta - traced the returned value is <c>false</c>, and if - the function is meta traced but has once detected that - the tracer proc is invalid, the returned value is [].</p> + <p>Returns the meta-trace tracer process or port for this + function, if it has one. If the function is not + meta-traced, the returned value is <c>false</c>. If + the function is meta-traced but has once detected that + the tracer process is invalid, the returned value is [].</p> </item> <tag><c>meta_match_spec</c></tag> <item> - <p>Return the meta trace match specification for this - function, if it has one. If the function is meta traced + <p>Returns the meta-trace match specification for this + function, if it has one. If the function is meta-traced but has no match specification defined, the returned value is <c>[]</c>.</p> </item> <tag><c>call_count</c></tag> <item> - <p>Return the call count value for this function or + <p>Returns the call count value for this function or <c>true</c> for the pseudo function <c>on_load</c> if call - count tracing is active. Return <c>false</c> otherwise. + count tracing is active. Otherwise <c>false</c> is returned. See also <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p> </item> <tag><c>call_time</c></tag> <item> - <p>Return the call time values for this function or + <p>Returns the call time values for this function or <c>true</c> for the pseudo function <c>on_load</c> if call - time tracing is active. Returns <c>false</c> otherwise. + time tracing is active. Otherwise <c>false</c> is returned. The call time values returned, <c>[{Pid, Count, S, Us}]</c>, - is a list of each process that has executed the function and its specific counters. - See also + is a list of each process that executed the function + and its specific counters. See also <seealso marker="#trace_pattern/3">erlang:trace_pattern/3</seealso>.</p> </item> <tag><c>all</c></tag> <item> - <p>Return a list containing the <c>{<anno>Item</anno>, Value}</c> tuples - for all other items, or return <c>false</c> if no tracing + <p>Returns a list containing the + <c>{<anno>Item</anno>, Value}</c> tuples + for all other items, or returns <c>false</c> if no tracing is active for this function.</p> </item> </taglist> - <p>The actual return value will be <c>{<anno>Item</anno>, Value}</c>, where - <c>Value</c> is the requested information as described above. + <p>The return value is <c>{<anno>Item</anno>, Value}</c>, where + <c>Value</c> is the requested information as described earlier. If a pid for a dead process was given, or the name of a - non-existing function, <c>Value</c> will be <c>undefined</c>.</p> - <p>If <c><anno>PidOrFunc</anno></c> is the <c>on_load</c>, the information + non-existing function, <c>Value</c> is <c>undefined</c>.</p> + <p>If <c><anno>PidOrFunc</anno></c> is <c>on_load</c>, the information returned refers to the default value for code that will be loaded.</p> </desc> </func> + <func> <name name="trace_pattern" arity="2" clause_i="1"/> + <fsummary>Sets trace patterns for global call tracing.</fsummary> <type name="trace_pattern_mfa"/> <type name="trace_match_spec"/> - <fsummary>Set trace patterns for global call tracing</fsummary> <desc> <p>The same as <seealso marker="#trace_pattern/3">erlang:trace_pattern(MFA, MatchSpec, [])</seealso>, retained for backward compatibility.</p> </desc> </func> + <func> <name name="trace_pattern" arity="3"/> + <fsummary>Sets trace patterns for tracing of function calls.</fsummary> <type name="trace_pattern_mfa"/> <type name="trace_match_spec"/> <type name="trace_pattern_flag"/> - <fsummary>Set trace patterns for tracing of function calls</fsummary> <desc> - <p>This BIF is used to enable or disable call tracing for - exported functions. It must be combined with + <p>Enables or disables call tracing for + one or more functions. Must be combined with <seealso marker="#trace/3">erlang:trace/3</seealso> to set the <c>call</c> trace flag for one or more processes.</p> - <p>Conceptually, call tracing works like this: Inside - the Erlang virtual machine there is a set of processes to be - traced and a set of functions to be traced. Tracing will be - enabled on the intersection of the set. That is, if a process - included in the traced process set calls a function included - in the traced function set, the trace action will be taken. - Otherwise, nothing will happen.</p> - <p>Use - <seealso marker="#trace/3">erlang:trace/3</seealso> to - add or remove one or more processes to the set of traced - processes. Use <c>erlang:trace_pattern/2</c> to add or remove - exported functions to the set of traced functions.</p> - <p>The <c>erlang:trace_pattern/3</c> BIF can also add match - specifications to an exported function. A match specification - comprises a pattern that the arguments to the function must - match, a guard expression which must evaluate to <c>true</c> + <p>Conceptually, call tracing works as follows. Inside + the Erlang Virtual Machine, a set of processes and + a set of functions are to be traced. If a traced process + calls a traced function, the trace action is taken. + Otherwise, nothing happens.</p> + <p>To add or remove one or more processes to the set of traced + processes, use + <seealso marker="#trace/3">erlang:trace/3</seealso>.</p> + <p>To add or remove functions to the set of traced + functions, use <c>erlang:trace_pattern/3</c>.</p> + <p>The BIF <c>erlang:trace_pattern/3</c> can also add match + specifications to a function. A match specification + comprises a pattern that the function arguments must + match, a guard expression that must evaluate to <c>true</c>, and an action to be performed. The default action is to send a trace message. If the pattern does not match or the guard - fails, the action will not be executed.</p> - <p>The <c><anno>MFA</anno></c> argument should be a tuple like - <c>{Module, Function, Arity}</c> or the atom <c>on_load</c> - (described below). It can be the module, function, and arity - for an exported function (or a BIF in any module). - The <c>'_'</c> atom can be used to mean any of that kind. - Wildcards can be used in any of the following ways:</p> + fails, the action is not executed.</p> + <p>Argument <c><anno>MFA</anno></c> is to be a tuple, such as + <c>{Module, Function, Arity}</c>, or the atom <c>on_load</c> + (described in the following). It can be the module, function, + and arity for a function (or a BIF in any module). + The atom <c>'_'</c> can be used as a wild card in any of the + following ways:</p> <taglist> <tag><c>{Module,Function,'_'}</c></tag> <item> - <p>All exported functions of any arity named <c>Function</c> + <p>All functions of any arity named <c>Function</c> in module <c>Module</c>.</p> </item> <tag><c>{Module,'_','_'}</c></tag> <item> - <p>All exported functions in module <c>Module</c>.</p> + <p>All functions in module <c>Module</c>.</p> </item> <tag><c>{'_','_','_'}</c></tag> <item> - <p>All exported functions in all loaded modules.</p> + <p>All functions in all loaded modules.</p> </item> </taglist> <p>Other combinations, such as <c>{Module,'_',Arity}</c>, are - not allowed. Local functions will match wildcards only if - the <c>local</c> option is in the <c><anno>FlagList</anno></c>.</p> - <p>If the <c><anno>MFA</anno></c> argument is the atom <c>on_load</c>, - the match specification and flag list will be used on all + not allowed. Local functions match wild cards only if + option <c>local</c> is in <c><anno>FlagList</anno></c>.</p> + <p>If argument <c><anno>MFA</anno></c> is the atom <c>on_load</c>, + the match specification and flag list are used on all modules that are newly loaded.</p> - <p>The <c><anno>MatchSpec</anno></c> argument can take any of the following - forms:</p> + <p>Argument <c><anno>MatchSpec</anno></c> can take the + following forms:</p> <taglist> <tag><c>false</c></tag> <item> - <p>Disable tracing for the matching function(s). Any match - specification will be removed.</p> + <p>Disables tracing for the matching functions. + Any match specification is removed.</p> </item> <tag><c>true</c></tag> <item> - <p>Enable tracing for the matching function(s).</p> + <p>Enables tracing for the matching functions.</p> </item> <tag><c><anno>MatchSpecList</anno></c></tag> <item> <p>A list of match specifications. An empty list is - equivalent to <c>true</c>. See the ERTS User's Guide - for a description of match specifications.</p> + equivalent to <c>true</c>. For a description of match + specifications, see the User's Guide.</p> </item> <tag><c>restart</c></tag> <item> - <p>For the <c><anno>FlagList</anno></c> option <c>call_count</c> and <c>call_time</c>: - restart the existing counters. The behaviour is undefined + <p>For the <c><anno>FlagList</anno></c> options <c>call_count</c> + and <c>call_time</c>: restarts + the existing counters. The behavior is undefined for other <c><anno>FlagList</anno></c> options.</p> </item> <tag><c>pause</c></tag> <item> - <p>For the <c><anno>FlagList</anno></c> option <c>call_count</c> and <c>call_time</c>: pause - the existing counters. The behaviour is undefined for - other <c>FlagList</c> options.</p> + <p>For the <c><anno>FlagList</anno></c> options + <c>call_count</c> and <c>call_time</c>: pauses + the existing counters. The behavior is undefined for + other <c><anno>FlagList</anno></c> options.</p> </item> </taglist> - <p>The <c><anno>FlagList</anno></c> parameter is a list of options. - The following options are allowed:</p> + <p>Parameter <c><anno>FlagList</anno></c> is a list of options. + The following are the valid options:</p> <taglist> <tag><c>global</c></tag> <item> - <p>Turn on or off call tracing for global function calls + <p>Turns on or off call tracing for global function calls (that is, calls specifying the module explicitly). Only - exported functions will match and only global calls will - generate trace messages. This is the default.</p> + exported functions match and only global calls + generate trace messages. <em>This is the default</em>.</p> </item> <tag><c>local</c></tag> <item> - <p>Turn on or off call tracing for all types of function - calls. Trace messages will be sent whenever any of + <p>Turns on or off call tracing for all types of function + calls. Trace messages are sent whenever any of the specified functions are called, regardless of how they - are called. If the <c>return_to</c> flag is set for - the process, a <c>return_to</c> message will also be sent + are called. If flag <c>return_to</c> is set for + the process, a <c>return_to</c> message is also sent when this function returns to its caller.</p> </item> <tag><c>meta | {meta, <anno>Pid</anno>}</c></tag> <item> - <p>Turn on or off meta tracing for all types of function - calls. Trace messages will be sent to the tracer process + <p>Turns on or off meta-tracing for all types of function + calls. Trace messages are sent to the tracer process or port <c><anno>Pid</anno></c> whenever any of the specified functions are called, regardless of how they are called. - If no <c><anno>Pid</anno></c> is specified, <c>self()</c> is used as a - default tracer process.</p> - <p>Meta tracing traces all processes and does not care + If no <c><anno>Pid</anno></c> is specified, + <c>self()</c> is used as a default tracer process.</p> + <p>Meta-tracing traces all processes and does not care about the process trace flags set by <c>trace/3</c>, the trace flags are instead fixed to <c>[call, timestamp]</c>.</p> - <p>The match spec function <c>{return_trace}</c> works with - meta trace and send its trace message to the same tracer - process.</p> + <p>The match specification function <c>{return_trace}</c> + works with meta-trace and sends its trace message to the + same tracer process.</p> </item> <tag><c>call_count</c></tag> <item> <p>Starts (<c><anno>MatchSpec</anno> == true</c>) or stops - (<c><anno>MatchSpec</anno> == false</c>) call count tracing for all - types of function calls. For every function a counter is + (<c><anno>MatchSpec</anno> == false</c>) + call count tracing for all + types of function calls. For every function, a counter is incremented when the function is called, in any process. No process trace flags need to be activated.</p> <p>If call count tracing is started while already running, - the count is restarted from zero. Running counters can be - paused with <c><anno>MatchSpec</anno> == pause</c>. Paused and running - counters can be restarted from zero with + the count is restarted from zero. To pause running + counters, use <c><anno>MatchSpec</anno> == pause</c>. + Paused and running counters can be restarted from zero with <c><anno>MatchSpec</anno> == restart</c>.</p> - <p>The counter value can be read with + <p>To read the counter value, use <seealso marker="#trace_info/2">erlang:trace_info/2</seealso>.</p> </item> <tag><c>call_time</c></tag> <item> <p>Starts (<c><anno>MatchSpec</anno> == true</c>) or stops - (<c><anno>MatchSpec</anno> == false</c>) call time tracing for all - types of function calls. For every function a counter is - incremented when the function is called. Time spent in the function - is accumulated in two other counters, seconds and micro-seconds. + (<c><anno>MatchSpec</anno> == false</c>) call time + tracing for all + types of function calls. For every function, a counter is + incremented when the function is called. + Time spent in the function is accumulated in + two other counters, seconds and microseconds. The counters are stored for each call traced process.</p> <p>If call time tracing is started while already running, - the count and time is restarted from zero. Running counters can be - paused with <c><anno>MatchSpec</anno> == pause</c>. Paused and running - counters can be restarted from zero with + the count and time is restarted from zero. To pause + running counters, use <c><anno>MatchSpec</anno> == pause</c>. + Paused and running counters can be restarted from zero with <c><anno>MatchSpec</anno> == restart</c>.</p> - <p>The counter value can be read with + <p>To read the counter value, use <seealso marker="#trace_info/2">erlang:trace_info/2</seealso>.</p> </item> - </taglist> - <p>The <c>global</c> and <c>local</c> options are mutually - exclusive and <c>global</c> is the default (if no options are - specified). The <c>call_count</c> and <c>meta</c> options - perform a kind of local tracing, and can also not be combined - with <c>global</c>. A function can be either globally or + <p>The options <c>global</c> and <c>local</c> are mutually + exclusive, and <c>global</c> is the default (if no options are + specified). The options <c>call_count</c> and <c>meta</c> + perform a kind of local tracing, and cannot be combined + with <c>global</c>. A function can be globally or locally traced. If global tracing is specified for a - specified set of functions; local, meta, call time and call count - tracing for the matching set of local functions will be - disabled, and vice versa.</p> + set of functions, then local, meta, call time, and call count + tracing for the matching set of local functions is + disabled, and conversely.</p> <p>When disabling trace, the option must match the type of trace - that is set on the function, so that local tracing must be - disabled with the <c>local</c> option and global tracing with - the <c>global</c> option (or no option at all), and so forth.</p> - <p>There is no way to directly change part of a match - specification list. If a function has a match specification, - you can replace it with a completely new one. If you need to - change an existing match specification, use the + set on the function. That is, local tracing must be + disabled with option <c>local</c> and global tracing with + option <c>global</c> (or no option), and so forth.</p> + <p>Part of a match specification list cannot be changed directly. + If a function has a match specification, it can be replaced + with a new one. To change an existing match specification, + use the BIF <seealso marker="#trace_info/2">erlang:trace_info/2</seealso> - BIF to retrieve the existing match specification.</p> - <p>Returns the number of exported functions that matched - the <c><anno>MFA</anno></c> argument. This will be zero if none matched at - all.</p> + to retrieve the existing match specification.</p> + <p>Returns the number of functions matching + argument <c><anno>MFA</anno></c>. This is zero if none matched.</p> </desc> </func> + <func> <name name="trunc" arity="1"/> - <fsummary>Return an integer by the truncating a number</fsummary> + <fsummary>Returns an integer by truncating a number</fsummary> <desc> - <p>Returns an integer by the truncating <c><anno>Number</anno></c>.</p> + <p>Returns an integer by truncating <c><anno>Number</anno></c>, + for example:</p> <pre> > <input>trunc(5.5).</input> 5</pre> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="tuple_size" arity="1"/> - <fsummary>Return the size of a tuple</fsummary> + <fsummary>Returns the size of a tuple.</fsummary> <desc> - <p>Returns an integer which is the number of elements in <c><anno>Tuple</anno></c>.</p> + <p>Returns an integer that is the number of elements in + <c><anno>Tuple</anno></c>, for example:</p> <pre> > <input>tuple_size({morni, mulle, bwange}).</input> 3</pre> <p>Allowed in guard tests.</p> </desc> </func> + <func> <name name="tuple_to_list" arity="1"/> - <fsummary>Convert a tuple to a list</fsummary> + <fsummary>Converts a tuple to a list.</fsummary> <desc> - <p>Returns a list which corresponds to <c><anno>Tuple</anno></c>. - <c><anno>Tuple</anno></c> may contain any Erlang terms.</p> + <p>Returns a list corresponding to <c><anno>Tuple</anno></c>. + <c><anno>Tuple</anno></c> can contain any Erlang terms.</p> + <p>Example:</p> <pre> > <input>tuple_to_list({share, {'Ericsson_B', 163}}).</input> [share,{'Ericsson_B',163}]</pre> </desc> </func> + <func> <name name="universaltime" arity="0"/> - <fsummary>Current date and time according to Universal Time Coordinated (UTC)</fsummary> + <fsummary>Current date and time according to Universal Time Coordinated (UTC).</fsummary> <desc> <p>Returns the current date and time according to Universal - Time Coordinated (UTC), also called GMT, in the form + Time Coordinated (UTC) in the form <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c> if - supported by the underlying operating system. If not, - <c>erlang:universaltime()</c> is equivalent to + supported by the underlying OS. + Otherwise <c>erlang:universaltime()</c> is equivalent to <c>erlang:localtime()</c>.</p> + <p>Example:</p> <pre> > <input>erlang:universaltime().</input> {{1996,11,6},{14,18,43}}</pre> </desc> </func> + <func> <name name="universaltime_to_localtime" arity="1"/> - <fsummary>Convert from Universal Time Coordinated (UTC) to local date and time</fsummary> + <fsummary>Converts from Universal Time Coordinated (UTC) to local date and time.</fsummary> <desc> <p>Converts Universal Time Coordinated (UTC) date and time to - local date and time, if this is supported by the underlying - OS. Otherwise, no conversion is done, and + local date and time in the form + <c>{{Year, Month, Day}, {Hour, Minute, Second}}</c> if + supported by the underlying OS. + Otherwise no conversion is done, and <c><anno>Universaltime</anno></c> is returned.</p> + <p>Example:</p> <pre> > <input>erlang:universaltime_to_localtime({{1996,11,6},{14,18,43}}).</input> {{1996,11,7},{15,18,43}}</pre> - <p>Failure: <c>badarg</c> if <c>Universaltime</c> does not denote - a valid date and time.</p> + <p>Failure: <c>badarg</c> if <c>Universaltime</c> denotes + an invalid date and time.</p> + </desc> + </func> + + <func> + <name name="unique_integer" arity="0"/> + <fsummary>Get a unique integer value</fsummary> + <desc> + <p>Generates and returns an + <seealso marker="doc/efficiency_guide:advanced#unique_integers">integer + unique on current runtime system instance</seealso>. The same as calling + <seealso marker="#unique_integer/1"><c>erlang:unique_integer([])</c></seealso>.</p> + </desc> + </func> + <func> + <name name="unique_integer" arity="1"/> + <fsummary>Get a unique integer value</fsummary> + <desc> + <p>Generates and returns an + <seealso marker="doc/efficiency_guide:advanced#unique_integers">integer + unique on current runtime system + instance</seealso>. The integer is unique in the + sense that this BIF, using the same set of + modifiers, will not return the same integer more + than once on the current runtime system instance. + Each integer value can of course be constructed + by other means.</p> + + <p>By default, when <c>[]</c> is passed as + <c><anno>ModifierList</anno></c>, both negative and + positive integers can be returned. This in order + to utilize the range of integers that do + not need heap memory allocation as much as possible. + By default the returned integers are also only + guaranteed to be unique, that is, any returned integer + can be smaller or larger than previously + returned integers.</p> + + <p>Valid <c><anno>Modifier</anno></c>s:</p> + <taglist> + + <tag>positive</tag> + <item><p>Return only positive integers.</p> + <p>Note that by passing the <c>positive</c> modifier + you will get heap allocated integers (bignums) + quicker.</p> + </item> + + <tag>monotonic</tag> + <item><p>Return + <seealso marker="time_correction#Strictly_Monotonically_Increasing">strictly + monotonically increasing</seealso> integers + corresponding to creation time. That is, the integer + returned will always be larger than previously + returned integers on the current runtime system + instance.</p> + <p>These values can be used to determine order between events + on the runtime system instance. That is, if both + <c>X = erlang:unique_integer([monotonic])</c> and + <c>Y = erlang:unique_integer([monotonic])</c> are + executed by different processes (or the same + process) on the same runtime system instance and + <c>X < Y</c> we know that <c>X</c> was created + before <c>Y</c>.</p> + <warning><p>Strictly monotonically increasing values + are inherently quite expensive to generate and scales + poorly. This is because the values need to be + synchronized between cpu cores. That is, do not pass the <c>monotonic</c> + modifier unless you really need strictly monotonically + increasing values.</p></warning> + </item> + + </taglist> + + <p>All valid <c><anno>Modifier</anno></c>s + can be combined. Repeated (valid) + <c><anno>Modifier</anno></c>s in the <c>ModifierList</c> + are ignored.</p> + + <note><p>Note that the set of integers returned by + <c>unique_integer/1</c> using different sets of + <c><anno>Modifier</anno></c>s <em>will overlap</em>. + For example, by calling <c>unique_integer([monotonic])</c>, + and <c>unique_integer([positive, monotonic])</c> + repeatedly, you will eventually see some integers being + returned by both calls.</p></note> + + <p>Failures:</p> + <taglist> + <tag><c>badarg</c></tag> + <item>if <c><anno>ModifierList</anno></c> is not a + proper list.</item> + <tag><c>badarg</c></tag> + <item>if <c><anno>Modifier</anno></c> is not a + valid modifier.</item> + </taglist> </desc> </func> <func> <name name="unlink" arity="1"/> - <fsummary>Remove a link, if there is one, to another process or port</fsummary> + <fsummary>Removes a link to another process or port.</fsummary> <desc> <p>Removes the link, if there is one, between the calling - process and the process or port referred to by <c><anno>Id</anno></c>.</p> + process and the process or port referred to by + <c><anno>Id</anno></c>.</p> <p>Returns <c>true</c> and does not fail, even if there is no - link to <c><anno>Id</anno></c>, or if <c><anno>Id</anno></c> does not exist.</p> - <p>Once <c>unlink(<anno>Id</anno>)</c> has returned it is guaranteed that + link to <c><anno>Id</anno></c>, or if <c><anno>Id</anno></c> + does not exist.</p> + <p>Once <c>unlink(<anno>Id</anno>)</c> has returned, + it is guaranteed that the link between the caller and the entity referred to by - <c><anno>Id</anno></c> has no effect on the caller in the future (unless - the link is setup again). If caller is trapping exits, an - <c>{'EXIT', <anno>Id</anno>, _}</c> message due to the link might have - been placed in the caller's message queue prior to the call, - though. Note, the <c>{'EXIT', <anno>Id</anno>, _}</c> message can be the - result of the link, but can also be the result of <c><anno>Id</anno></c> - calling <c>exit/2</c>. Therefore, it <em>may</em> be - appropriate to cleanup the message queue when trapping exits - after the call to <c>unlink(<anno>Id</anno>)</c>, as follow:</p> + <c><anno>Id</anno></c> has no effect on the caller + in the future (unless + the link is setup again). If the caller is trapping exits, an + <c>{'EXIT', <anno>Id</anno>, _}</c> message from the link + can have been placed in the caller's message queue before + the call.</p> + <p>Notice that the <c>{'EXIT', <anno>Id</anno>, _}</c> + message can be the + result of the link, but can also be the result of <c>Id</c> + calling <c>exit/2</c>. Therefore, it <em>can</em> be + appropriate to clean up the message queue when trapping exits + after the call to <c>unlink(<anno>Id</anno>)</c>, as follows:</p> <code type="none"> - unlink(Id), receive {'EXIT', Id, _} -> @@ -7211,23 +8956,25 @@ ok true end</code> <note> - <p>Prior to OTP release R11B (erts version 5.5) <c>unlink/1</c> - behaved completely asynchronous, i.e., the link was active + <p>Prior to OTP release R11B (ERTS version 5.5) <c>unlink/1</c> + behaved completely asynchronously, i.e., the link was active until the "unlink signal" reached the linked entity. This - had one undesirable effect, though. You could never know when + had an undesirable effect, as you could never know when you were guaranteed <em>not</em> to be effected by the link.</p> - <p>Current behavior can be viewed as two combined operations: + <p>The current behavior can be viewed as two combined operations: asynchronously send an "unlink signal" to the linked entity and ignore any future results of the link.</p> </note> </desc> </func> + <func> <name name="unregister" arity="1"/> - <fsummary>Remove the registered name for a process (or port)</fsummary> + <fsummary>Removes the registered name for a process (or port).</fsummary> <desc> - <p>Removes the registered name <c><anno>RegName</anno></c>, associated with a - pid or a port identifier.</p> + <p>Removes the registered name <c><anno>RegName</anno></c> + associated with a + process identifier or a port identifier, for example:</p> <pre> > <input>unregister(db).</input> true</pre> @@ -7236,31 +8983,34 @@ true</pre> name.</p> </desc> </func> + <func> <name name="whereis" arity="1"/> - <fsummary>Get the pid (or port) with a given registered name</fsummary> + <fsummary>Gets the pid (or port) with a given registered name.</fsummary> <desc> - <p>Returns the pid or port identifier with the registered name - <c>RegName</c>. Returns <c>undefined</c> if the name is not - registered.</p> + <p>Returns the process identifier or port identifier with + the registered name <c>RegName</c>. Returns <c>undefined</c> + if the name is not registered.</p> + <p>Example:</p> <pre> > <input>whereis(db).</input> <0.43.0></pre> </desc> </func> + <func> <name name="yield" arity="0"/> - <fsummary>Let other processes get a chance to execute</fsummary> + <fsummary>Lets other processes get a chance to execute.</fsummary> <desc> - <p>Voluntarily let other processes (if any) get a chance to + <p>Voluntarily lets other processes (if any) get a chance to execute. Using <c>erlang:yield()</c> is similar to <c>receive after 1 -> ok end</c>, except that <c>yield()</c> is faster.</p> <warning><p>There is seldom or never any need to use this BIF, - especially in the SMP-emulator as other processes will have a - chance to run in another scheduler thread anyway. - Using this BIF without a thorough grasp of how the scheduler - works may cause performance degradation.</p></warning> + especially in the SMP emulator, as other processes have a + chance to run in another scheduler thread anyway. + Using this BIF without a thorough grasp of how the scheduler + works can cause performance degradation.</p></warning> </desc> </func> </funcs> |