diff options
Diffstat (limited to 'lib/stdlib/doc/src/io.xml')
| -rw-r--r-- | lib/stdlib/doc/src/io.xml | 364 |
1 files changed, 237 insertions, 127 deletions
diff --git a/lib/stdlib/doc/src/io.xml b/lib/stdlib/doc/src/io.xml index e6d262466c..90f24c4cbc 100644 --- a/lib/stdlib/doc/src/io.xml +++ b/lib/stdlib/doc/src/io.xml @@ -4,7 +4,7 @@ <erlref> <header> <copyright> - <year>1996</year><year>2011</year> + <year>1996</year><year>2013</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -28,9 +28,9 @@ <rev></rev> </header> <module>io</module> - <modulesummary>Standard IO Server Interface Functions</modulesummary> + <modulesummary>Standard I/O Server Interface Functions</modulesummary> <description> - <p>This module provides an interface to standard Erlang IO servers. + <p>This module provides an interface to standard Erlang I/O servers. The output functions all return <c>ok</c> if they are successful, or exit if they are not.</p> <p>In the following description, all functions have an optional @@ -38,17 +38,16 @@ process which handles the IO protocols. Normally, it is the <c>IoDevice</c> returned by <seealso marker="kernel:file#open/2">file:open/2</seealso>.</p> - <p>For a description of the IO protocols refer to the STDLIB Users Guide.</p> + <p>For a description of the IO protocols refer to the <seealso marker="io_protocol">STDLIB User's Guide</seealso>.</p> <warning> <p>As of R13A, data supplied to the <seealso marker="#put_chars/2">put_chars</seealso> function should be in the <seealso marker="unicode#type-chardata"><c>unicode:chardata()</c></seealso> format. This means that programs supplying binaries to this function need to convert them to UTF-8 - before trying to output the data on an - <c>io_device()</c>.</p> + before trying to output the data on an IO device.</p> - <p>If an io_device() is set in binary mode, the functions <seealso + <p>If an IO device is set in binary mode, the functions <seealso marker="#get_chars/3">get_chars</seealso> and <seealso marker="#get_line/2">get_line</seealso> may return binaries instead of lists. The binaries will, as of R13A, be encoded in @@ -68,9 +67,9 @@ <datatype> <name name="device"/> <desc> - <p>Either <c>standard_io</c>, <c>standard_error</c>, a + <p>An IO device. Either <c>standard_io</c>, <c>standard_error</c>, a registered name, or a pid handling IO protocols (returned from - <seealso marker="kernel:file#open/2">file:open/2</seealso>).</p> + <seealso marker="kernel:file#open/2">file:open/2</seealso>).</p> </desc> </datatype> <datatype> @@ -89,17 +88,14 @@ <name name="format"/> </datatype> <datatype> - <name name="line"/> + <name name="location"/> </datatype> <datatype> <name name="prompt"/> </datatype> <datatype> - <name name="request_error"/> - </datatype> - <datatype> - <name name="error_description"/> - <desc><p>Whatever the I/O-server sends.</p></desc> + <name name="server_no_data"/> + <desc><p>What the I/O-server sends when there is no data.</p></desc> </datatype> </datatypes> @@ -107,11 +103,11 @@ <func> <name name="columns" arity="0"/> <name name="columns" arity="1"/> - <fsummary>Get the number of columns of a device</fsummary> + <fsummary>Get the number of columns of an IO device</fsummary> <desc> <p>Retrieves the number of columns of the <c><anno>IoDevice</anno></c> (i.e. the width of a terminal). The function - only succeeds for terminal devices, for all other devices + only succeeds for terminal devices, for all other IO devices the function returns <c>{error, enotsup}</c></p> </desc> </func> @@ -120,7 +116,7 @@ <name name="put_chars" arity="2"/> <fsummary>Write a list of characters</fsummary> <desc> - <p>Writes the characters of <c><anno>CharData</anno></c> to the io_server() + <p>Writes the characters of <c><anno>CharData</anno></c> to the I/O server (<c><anno>IoDevice</anno></c>).</p> </desc> </func> @@ -135,6 +131,7 @@ <func> <name name="get_chars" arity="2"/> <name name="get_chars" arity="3"/> + <type name="server_no_data"/> <fsummary>Read a specified number of characters</fsummary> <desc> <p>Reads <c><anno>Count</anno></c> characters from standard input @@ -143,19 +140,19 @@ <taglist> <tag><c><anno>Data</anno></c></tag> <item> - <p>The input characters. If the device supports Unicode, + <p>The input characters. If the IO device supports Unicode, the data may represent codepoints larger than 255 (the - latin1 range). If the io_server() is set to deliver + latin1 range). If the I/O server is set to deliver binaries, they will be encoded in UTF-8 (regardless of if - the device actually supports Unicode or not).</p> + the IO device actually supports Unicode or not).</p> </item> <tag><c>eof</c></tag> <item> <p>End of file was encountered.</p> </item> - <tag><c>{error,<anno>Reason</anno>}</c></tag> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> <item> - <p>Other (rare) error condition, for instance <c>{error,estale}</c> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> if reading from an NFS file system.</p> </item> </taglist> @@ -164,6 +161,7 @@ <func> <name name="get_line" arity="1"/> <name name="get_line" arity="2"/> + <type name="server_no_data"/> <fsummary>Read a line</fsummary> <desc> <p>Reads a line from the standard input (<c><anno>IoDevice</anno></c>), @@ -172,19 +170,19 @@ <tag><c><anno>Data</anno></c></tag> <item> <p>The characters in the line terminated by a LF (or end of - file). If the device supports Unicode, + file). If the IO device supports Unicode, the data may represent codepoints larger than 255 (the - latin1 range). If the io_server() is set to deliver + latin1 range). If the I/O server is set to deliver binaries, they will be encoded in UTF-8 (regardless of if - the device actually supports Unicode or not).</p> + the IO device actually supports Unicode or not).</p> </item> <tag><c>eof</c></tag> <item> <p>End of file was encountered.</p> </item> - <tag><c>{error,<anno>Reason</anno>}</c></tag> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> <item> - <p>Other (rare) error condition, for instance <c>{error,estale}</c> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> if reading from an NFS file system.</p> </item> </taglist> @@ -195,7 +193,7 @@ <name name="getopts" arity="1"/> <fsummary>Get the supported options and values from an I/O-server</fsummary> <desc> - <p>This function requests all available options and their current values for a specific io_device(). Example:</p> + <p>This function requests all available options and their current values for a specific IO device. Example:</p> <pre> 1> <input>{ok,F} = file:open("/dev/null",[read]).</input> {ok,<0.42.0>} @@ -213,34 +211,46 @@ </desc> </func> <func> + <name name="printable_range" arity="0"/> + <fsummary>Get user requested printable character range</fsummary> + <desc> + <p>Return the user requested range of printable Unicode characters.</p> + <p>The user can request a range of characters that are to be considered printable in heuristic detection of strings by the shell and by the formatting functions. This is done by supplying <c>+pc <range></c> when starting Erlang.</p> + <p>Currently the only valid values for <c><range></c> are <c>latin1</c> and <c>unicode</c>. <c>latin1</c> means that only code points below 256 (with the exception of control characters etc) will be considered printable. <c>unicode</c> means that all printable characters in all unicode character ranges are considered printable by the io functions.</p> + <p>By default, Erlang is started so that only the <c>latin1</c> range of characters will indicate that a list of integers is a string.</p> + <p>The simplest way to utilize the setting is to call <seealso marker="io_lib#printable_list/1">io_lib:printable_list/1</seealso>, which will use the return value of this function to decide if a list is a string of printable characters or not.</p> + <note><p>In the future, this function may return more values and ranges. It is recommended to use the io_lib:printable_list/1 function to avoid compatibility problems.</p></note> + </desc> + </func> + <func> <name name="setopts" arity="1"/> <name name="setopts" arity="2"/> <fsummary>Set options</fsummary> <desc> - <p>Set options for the io_device() (<c><anno>IoDevice</anno></c>).</p> + <p>Set options for the standard IO device (<c><anno>IoDevice</anno></c>).</p> <p>Possible options and values vary depending on the actual - io_device(). For a list of supported options and their current values - on a specific device, use the <seealso + IO device. For a list of supported options and their current values + on a specific IO device, use the <seealso marker="#getopts/1">getopts/1</seealso> function.</p> - <p>The options and values supported by the current OTP io_devices are:</p> + <p>The options and values supported by the current OTP IO devices are:</p> <taglist> <tag><c>binary, list or {binary, boolean()}</c></tag> <item> - <p>If set in binary mode (binary or {binary,true}), the io_server() sends binary data (encoded in UTF-8) as answers to the get_line, get_chars and, if possible, get_until requests (see the I/O protocol description in STDLIB User's Guide for details). The immediate effect is that <c>get_chars/2,3</c> and <c>get_line/1,2</c> return UTF-8 binaries instead of lists of chars for the affected device.</p> - <p>By default, all io_devices in OTP are set in list mode, but the io functions can handle any of these modes and so should other, user written, modules behaving as clients to I/O-servers.</p> - <p>This option is supported by the standard shell (group.erl), the 'oldshell' (user.erl) and the file I/O servers.</p> + <p>If set in binary mode (<c>binary</c> or <c>{binary, true}</c>), the I/O server sends binary data (encoded in UTF-8) as answers to the <c>get_line</c>, <c>get_chars</c> and, if possible, <c>get_until</c> requests (see the I/O protocol description in <seealso marker="io_protocol">STDLIB User's Guide</seealso> for details). The immediate effect is that <c>get_chars/2,3</c> and <c>get_line/1,2</c> return UTF-8 binaries instead of lists of chars for the affected IO device.</p> + <p>By default, all IO devices in OTP are set in list mode, but the I/O functions can handle any of these modes and so should other, user written, modules behaving as clients to I/O-servers.</p> + <p>This option is supported by the standard shell (<c>group.erl</c>), the 'oldshell' (<c>user.erl</c>) and the file I/O servers.</p> </item> <tag><c>{echo, boolean()}</c></tag> <item> - <p>Denotes if the terminal should echo input. Only supported for the standard shell I/O-server (group.erl)</p> + <p>Denotes if the terminal should echo input. Only supported for the standard shell I/O-server (<c>group.erl</c>)</p> </item> <tag><c>{expand_fun, expand_fun()}</c></tag> <item> <p>Provide a function for tab-completion (expansion) - like the erlang shell. This function is called - when the user presses the Tab key. The expansion is + like the Erlang shell. This function is called + when the user presses the TAB key. The expansion is active when calling line-reading functions such as <c>get_line/1,2</c>.</p> <p>The function is called with the current line, upto @@ -253,25 +263,25 @@ will be printed and the current input line will be written once again.</p> <p>Trivial example (beep on anything except empty line, which - is expanded to "quit"):</p> + is expanded to <c>"quit"</c>):</p> <code type="none"> fun("") -> {yes, "quit", []}; (_) -> {no, "", ["quit"]} end</code> - <p>This option is supported by the standard shell only (group.erl).</p> + <p>This option is supported by the standard shell only (<c>group.erl</c>).</p> </item> <tag><c>{encoding, latin1 | unicode}</c></tag> <item> - <p>Specifies how characters are input or output from or to the actual device, implying that i.e. a terminal is set to handle Unicode input and output or a file is set to handle UTF-8 data encoding.</p> - <p>The option <em>does not</em> affect how data is returned from the io-functions or how it is sent in the I/O-protocol, it only affects how the io_device() is to handle Unicode characters towards the "physical" device.</p> - <p>The standard shell will be set for either unicode or latin1 encoding when the system is started. The actual encoding is set with the help of the "LANG" or "LC_CTYPE" environment variables on Unix-like system or by other means on other systems. The bottom line is that the user can input Unicode characters and the device will be in {encoding, unicode} mode if the device supports it. The mode can be changed, if the assumption of the runtime system is wrong, by setting this option.</p> - <p>The io_device() used when Erlang is started with the "-oldshell" or "-noshell" flags is by default set to latin1 encoding, meaning that any characters beyond codepoint 255 will be escaped and that input is expected to be plain 8-bit ISO-latin-1. If the encoding is changed to Unicode, input and output from the standard file descriptors will be in UTF-8 (regardless of operating system).</p> - <p>Files can also be set in {encoding, unicode}, meaning that data is written and read as UTF-8. More encodings are possible for files, see below.</p> - <p>{encoding, unicode | latin1} is supported by both the standard shell (group.erl including werl on windows), the 'oldshell' (user.erl) and the file I/O servers.</p> + <p>Specifies how characters are input or output from or to the actual IO device, implying that i.e. a terminal is set to handle Unicode input and output or a file is set to handle UTF-8 data encoding.</p> + <p>The option <em>does not</em> affect how data is returned from the I/O functions or how it is sent in the I/O-protocol, it only affects how the IO device is to handle Unicode characters towards the "physical" device.</p> + <p>The standard shell will be set for either Unicode or latin1 encoding when the system is started. The actual encoding is set with the help of the <c>LANG</c> or <c>LC_CTYPE</c> environment variables on Unix-like system or by other means on other systems. The bottom line is that the user can input Unicode characters and the IO device will be in <c>{encoding, unicode}</c> mode if the IO device supports it. The mode can be changed, if the assumption of the runtime system is wrong, by setting this option.</p> + <p>The IO device used when Erlang is started with the "-oldshell" or "-noshell" flags is by default set to latin1 encoding, meaning that any characters beyond codepoint 255 will be escaped and that input is expected to be plain 8-bit ISO-latin-1. If the encoding is changed to Unicode, input and output from the standard file descriptors will be in UTF-8 (regardless of operating system).</p> + <p>Files can also be set in <c>{encoding, unicode}</c>, meaning that data is written and read as UTF-8. More encodings are possible for files, see below.</p> + <p><c>{encoding, unicode | latin1}</c> is supported by both the standard shell (<c>group.erl</c> including <c>werl</c> on Windows®), the 'oldshell' (<c>user.erl</c>) and the file I/O servers.</p> </item> <tag><c>{encoding, utf8 | utf16 | utf32 | {utf16,big} | {utf16,little} | {utf32,big} | {utf32,little}}</c></tag> <item> <p>For disk files, the encoding can be set to various UTF variants. This will have the effect that data is expected to be read as the specified encoding from the file and the data will be written in the specified encoding to the disk file.</p> - <p>{encoding, utf8} will have the same effect as {encoding,unicode} on files.</p> + <p><c>{encoding, utf8}</c> will have the same effect as <c>{encoding, unicode}</c> on files.</p> <p>The extended encodings are only supported on disk files (opened by the <seealso marker="kernel:file#open/2">file:open/2</seealso> function)</p> </item> </taglist> @@ -289,6 +299,7 @@ <func> <name name="read" arity="1"/> <name name="read" arity="2"/> + <type name="server_no_data"/> <fsummary>Read a term</fsummary> <desc> <p>Reads a term <c><anno>Term</anno></c> from the standard input @@ -307,29 +318,43 @@ <item> <p>The parsing failed.</p> </item> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> + <item> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> + if reading from an NFS file system.</p> + </item> </taglist> </desc> </func> <func> <name name="read" arity="3"/> + <name name="read" arity="4"/> + <type name="server_no_data"/> <fsummary>Read a term</fsummary> <desc> <p>Reads a term <c><anno>Term</anno></c> from <c><anno>IoDevice</anno></c>, prompting it - with <c><anno>Prompt</anno></c>. Reading starts at line number - <c><anno>StartLine</anno></c>. It returns:</p> + with <c><anno>Prompt</anno></c>. Reading starts at location + <c><anno>StartLocation</anno></c>. The argument + <c><anno>Options</anno></c> is passed on as the <c>Options</c> + argument of the <c>erl_scan:tokens/4</c> function. It returns:</p> <taglist> - <tag><c>{ok, Term, <anno>EndLine</anno>}</c></tag> + <tag><c>{ok, Term, <anno>EndLocation</anno>}</c></tag> <item> <p>The parsing was successful.</p> </item> - <tag><c>{eof, <anno>EndLine</anno>}</c></tag> + <tag><c>{eof, <anno>EndLocation</anno>}</c></tag> <item> <p>End of file was encountered.</p> </item> - <tag><c>{error, <anno>ErrorInfo</anno>, <anno>ErrorLine</anno>}</c></tag> + <tag><c>{error, <anno>ErrorInfo</anno>, <anno>ErrorLocation</anno>}</c></tag> <item> <p>The parsing failed.</p> </item> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> + <item> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> + if reading from an NFS file system.</p> + </item> </taglist> </desc> </func> @@ -377,10 +402,11 @@ ok</pre> applicable, it is used for both the field width and precision. The default padding character is <c>' '</c> (space).</p> <p><c>Mod</c> is the control sequence modifier. It is either a - single character (currently only 't', for unicode translation, - is supported) that changes the interpretation of Data.</p> - - <p>The following control sequences are available:</p> + single character (currently only <c>t</c>, for Unicode + translation, and <c>l</c>, for stopping <c>p</c> and + <c>P</c> from detecting printable characters, are supported) + that changes the interpretation of Data.</p> + <p>The following control sequences are available:</p> <taglist> <tag><c>~</c></tag> <item> @@ -394,18 +420,18 @@ ok</pre> which in turn defaults to 1. The following example illustrates:</p> <pre> -2> <input>io:fwrite("|~10.5c|~-10.5c|~5c|~n", [$a, $b, $c]).</input> +1> <input>io:fwrite("|~10.5c|~-10.5c|~5c|~n", [$a, $b, $c]).</input> | aaaaa|bbbbb |ccccc| ok</pre> - <p>If the Unicode translation modifier ('t') is in effect, + <p>If the Unicode translation modifier (<c>t</c>) is in effect, the integer argument can be any number representing a - valid unicode codepoint, otherwise it should be an integer + valid Unicode codepoint, otherwise it should be an integer less than or equal to 255, otherwise it is masked with 16#FF:</p> <pre> -1> <input>io:fwrite("~tc~n",[1024]).</input> +2> <input>io:fwrite("~tc~n",[1024]).</input> \x{400} ok -2> <input>io:fwrite("~c~n",[1024]).</input> +3> <input>io:fwrite("~c~n",[1024]).</input> ^@ ok</pre> @@ -437,29 +463,32 @@ ok</pre> </item> <tag><c>s</c></tag> <item> - <p>Prints the argument with the <c>string</c> syntax. The + <p>Prints the argument with the string syntax. The argument is, if no Unicode translation modifier is present, an - iolist(), a binary, or an atom. If the Unicode translation modifier ('t') is in effect, the argument is unicode:chardata(), meaning that binaries are in UTF-8. The characters + <c>iolist()</c>, a <c>binary()</c>, or an <c>atom()</c>. + If the Unicode translation modifier (<c>t</c>) is in effect, + the argument is <c>unicode:chardata()</c>, meaning that + binaries are in UTF-8. The characters are printed without quotes. The string is first truncated by the given precision and then padded and justified to the given field width. The default precision is the field width.</p> <p>This format can be used for printing any object and truncating the output so it fits a specified field:</p> <pre> -3> <input>io:fwrite("|~10w|~n", [{hey, hey, hey}]).</input> +1> <input>io:fwrite("|~10w|~n", [{hey, hey, hey}]).</input> |**********| ok -4> <input>io:fwrite("|~10s|~n", [io_lib:write({hey, hey, hey})]).</input> +2> <input>io:fwrite("|~10s|~n", [io_lib:write({hey, hey, hey})]).</input> |{hey,hey,h| -5> <input>io:fwrite("|~-10.8s|~n", [io_lib:write({hey, hey, hey})]).</input> +3> <input>io:fwrite("|~-10.8s|~n", [io_lib:write({hey, hey, hey})]).</input> |{hey,hey | ok</pre> <p>A list with integers larger than 255 is considered an error if the Unicode translation modifier is not given:</p> <pre> -1> <input>io:fwrite("~ts~n",[[1024]]).</input> +4> <input>io:fwrite("~ts~n",[[1024]]).</input> \x{400} ok -2> io:fwrite("~s~n",[[1024]]). +5> <input>io:fwrite("~s~n",[[1024]]).</input> ** exception exit: {badarg,[{io,format,[<0.26.0>,"~s~n",[[1024]]]}, ...</pre> </item> @@ -476,20 +505,22 @@ ok <p>Writes the data with standard syntax in the same way as <c>~w</c>, but breaks terms whose printed representation is longer than one line into many lines and indents each - line sensibly. It also tries to detect lists of printable - characters and to output these as strings. For example:</p> + line sensibly. It also tries to detect lists of + printable characters and to output these as strings. The + Unicode translation modifier is used for determining + what characters are printable. For example:</p> <pre> -5> <input>T = [{attributes,[[{id,age,1.50000},{mode,explicit},</input> +1> <input>T = [{attributes,[[{id,age,1.50000},{mode,explicit},</input> <input>{typename,"INTEGER"}], [{id,cho},{mode,explicit},{typename,'Cho'}]]},</input> <input>{typename,'Person'},{tag,{'PRIVATE',3}},{mode,implicit}].</input> ... -6> <input>io:fwrite("~w~n", [T]).</input> +2> <input>io:fwrite("~w~n", [T]).</input> [{attributes,[[{id,age,1.5},{mode,explicit},{typename, [73,78,84,69,71,69,82]}],[{id,cho},{mode,explicit},{typena me,'Cho'}]]},{typename,'Person'},{tag,{'PRIVATE',3}},{mode ,implicit}] ok -7> <input>io:fwrite("~62p~n", [T]).</input> +3> <input>io:fwrite("~62p~n", [T]).</input> [{attributes,[[{id,age,1.5}, {mode,explicit}, {typename,"INTEGER"}], @@ -505,7 +536,7 @@ ok</pre> <c>io:fwrite</c> or <c>io:format</c>. For example, using <c>T</c> above:</p> <pre> -8> <input>io:fwrite("Here T = ~62p~n", [T]).</input> +4> <input>io:fwrite("Here T = ~62p~n", [T]).</input> Here T = [{attributes,[[{id,age,1.5}, {mode,explicit}, {typename,"INTEGER"}], @@ -516,6 +547,31 @@ Here T = [{attributes,[[{id,age,1.5}, {tag,{'PRIVATE',3}}, {mode,implicit}] ok</pre> + <p>When the modifier <c>l</c> is given no detection of + printable character lists will take place. For example:</p> + <pre> +5> <input>S = [{a,"a"}, {b, "b"}].</input> +6> <input>io:fwrite("~15p~n", [S]).</input> +[{a,"a"}, + {b,"b"}] +ok +7> <input>io:fwrite("~15lp~n", [S]).</input> +[{a,[97]}, + {b,[98]}] +ok</pre> + <p>Binaries that look like UTF-8 encoded strings will be + output with the string syntax if the Unicode translation + modifier is given:</p> + <pre> +9> <input>io:fwrite("~p~n",[[1024]]).</input> +[1024] +10> <input>io:fwrite("~tp~n",[[1024]]).</input> +"\x{400}" +11> <input>io:fwrite("~tp~n", [<<128,128>>]).</input> +<<128,128>> +12> <input>io:fwrite("~tp~n", [<<208,128>>]).</input> +<<"\x{400}"/utf8>> +ok</pre> </item> <tag><c>W</c></tag> <item> @@ -524,7 +580,7 @@ ok</pre> are printed. Anything below this depth is replaced with <c>...</c>. For example, using <c>T</c> above:</p> <pre> -9> <input>io:fwrite("~W~n", [T,9]).</input> +8> <input>io:fwrite("~W~n", [T,9]).</input> [{attributes,[[{id,age,1.5},{mode,explicit},{typename,...}], [{id,cho},{mode,...},{...}]]},{typename,'Person'}, {tag,{'PRIVATE',3}},{mode,implicit}] @@ -541,7 +597,7 @@ ok</pre> are printed. Anything below this depth is replaced with <c>...</c>. For example:</p> <pre> -10> <input>io:fwrite("~62P~n", [T,9]).</input> +9> <input>io:fwrite("~62P~n", [T,9]).</input> [{attributes,[[{id,age,1.5},{mode,explicit},{typename,...}], [{id,cho},{mode,...},{...}]]}, {typename,'Person'}, @@ -555,13 +611,13 @@ ok</pre> 10. A leading dash is printed for negative integers.</p> <p>The precision field selects base. For example:</p> <pre> -11> <input>io:fwrite("~.16B~n", [31]).</input> +1> <input>io:fwrite("~.16B~n", [31]).</input> 1F ok -12> <input>io:fwrite("~.2B~n", [-19]).</input> +2> <input>io:fwrite("~.2B~n", [-19]).</input> -10011 ok -13> <input>io:fwrite("~.36B~n", [5*36+35]).</input> +3> <input>io:fwrite("~.36B~n", [5*36+35]).</input> 5Z ok</pre> </item> @@ -573,22 +629,22 @@ ok</pre> <p>The prefix can be a possibly deep list of characters or an atom.</p> <pre> -14> <input>io:fwrite("~X~n", [31,"10#"]).</input> +1> <input>io:fwrite("~X~n", [31,"10#"]).</input> 10#31 ok -15> <input>io:fwrite("~.16X~n", [-31,"0x"]).</input> +2> <input>io:fwrite("~.16X~n", [-31,"0x"]).</input> -0x1F ok</pre> </item> <tag><c>#</c></tag> <item> <p>Like <c>B</c>, but prints the number with an Erlang style - '#'-separated base prefix.</p> + <c>#</c>-separated base prefix.</p> <pre> -16> <input>io:fwrite("~.10#~n", [31]).</input> +1> <input>io:fwrite("~.10#~n", [31]).</input> 10#31 ok -17> <input>io:fwrite("~.16#~n", [-31]).</input> +2> <input>io:fwrite("~.16#~n", [-31]).</input> -16#1F ok</pre> </item> @@ -622,10 +678,10 @@ ok</pre> </taglist> <p>If an error occurs, there is no output. For example:</p> <pre> -18> <input>io:fwrite("~s ~w ~i ~w ~c ~n",['abc def', 'abc def', {foo, 1},{foo, 1}, 65]).</input> +1> <input>io:fwrite("~s ~w ~i ~w ~c ~n",['abc def', 'abc def', {foo, 1},{foo, 1}, 65]).</input> abc def 'abc def' {foo,1} A ok -19> <input>io:fwrite("~s", [65]).</input> +2> <input>io:fwrite("~s", [65]).</input> ** exception exit: {badarg,[{io,format,[<0.22.0>,"~s","A"]}, {erl_eval,do_apply,5}, {shell,exprs,6}, @@ -633,13 +689,14 @@ ok {shell,eval_loop,3}]} in function io:o_request/2</pre> <p>In this example, an attempt was made to output the single - character '65' with the aid of the string formatting directive + character 65 with the aid of the string formatting directive "~s".</p> </desc> </func> <func> <name name="fread" arity="2"/> <name name="fread" arity="3"/> + <type name="server_no_data"/> <fsummary>Read formatted input</fsummary> <desc> <p>Reads characters from the standard input (<c><anno>IoDevice</anno></c>), @@ -664,7 +721,7 @@ ok return suppression character. It provides a method to specify a field which is to be omitted. <c>F</c> is the <c>field width</c> of the input field, <c>M</c> is an optional - translation modifier (of which 't' is the only currently + translation modifier (of which <c>t</c> is the only currently supported, meaning Unicode translation) and <c>C</c> determines the type of control sequence.</p> @@ -690,8 +747,8 @@ ok <tag><c>-</c></tag> <item> <p>An optional sign character is expected. A sign - character '-' gives the return value <c>-1</c>. Sign - character '+' or none gives <c>1</c>. The field width + character <c>-</c> gives the return value <c>-1</c>. Sign + character <c>+</c> or none gives <c>1</c>. The field width parameter is ignored. Leading white-space characters are not skipped.</p> </item> @@ -713,7 +770,7 @@ ok characters are stripped. An Erlang string (list of characters) is returned.</p> - <p>If Unicode translation is in effect (~ts), + <p>If Unicode translation is in effect (<c>~ts</c>), characters larger than 255 are accepted, otherwise not. With the translation modifier, the list returned may as a consequence also contain @@ -769,10 +826,15 @@ Prompt> <input><Character beyond latin1 range not printable in this medium> <item> <p>End of file was encountered.</p> </item> - <tag><c>{error, <anno>What</anno>}</c></tag> + <tag><c>{error, <anno>FreadError</anno>}</c></tag> + <item> + <p>The reading failed and <c>FreadError</c> gives a + hint about the error.</p> + </item> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> <item> <p>The read operation failed and the parameter - <c><anno>What</anno></c> gives a hint about the error.</p> + <c><anno>ErrorDescription</anno></c> gives a hint about the error.</p> </item> </taglist> </item> @@ -793,11 +855,11 @@ enter><input>:</input> <input>alan</input> <input>:</input> <input>joe</in <func> <name name="rows" arity="0"/> <name name="rows" arity="1"/> - <fsummary>Get the number of rows of a device</fsummary> + <fsummary>Get the number of rows of an IO device</fsummary> <desc> <p>Retrieves the number of rows of the <c><anno>IoDevice</anno></c> (i.e. the height of a terminal). The function - only succeeds for terminal devices, for all other devices + only succeeds for terminal devices, for all other IO devices the function returns <c>{error, enotsup}</c></p> </desc> </func> @@ -805,26 +867,40 @@ enter><input>:</input> <input>alan</input> <input>:</input> <input>joe</in <name name="scan_erl_exprs" arity="1"/> <name name="scan_erl_exprs" arity="2"/> <name name="scan_erl_exprs" arity="3"/> + <name name="scan_erl_exprs" arity="4"/> + <type name="server_no_data"/> <fsummary>Read and tokenize Erlang expressions</fsummary> <desc> <p>Reads data from the standard input (<c>IoDevice</c>), - prompting it with <c>Prompt</c>. Reading starts at line number - <c>StartLine</c> (1). The data is tokenized as if it were a - sequence of Erlang expressions until a final <c>'.'</c> is + prompting it with <c>Prompt</c>. Reading starts at location + <c>StartLocation</c> (<c>1</c>). The argument <c><anno>Options</anno></c> + is passed on as the <c>Options</c> argument of the + <c>erl_scan:tokens/4</c> function. The data is tokenized as if + it were a + sequence of Erlang expressions until a final dot (<c>.</c>) is reached. This token is also returned. It returns:</p> <taglist> - <tag><c>{ok, Tokens, EndLine}</c></tag> + <tag><c>{ok, Tokens, EndLocation}</c></tag> <item> <p>The tokenization succeeded.</p> </item> - <tag><c>{eof, EndLine}</c></tag> + <tag><c>{eof, EndLocation}</c></tag> <item> - <p>End of file was encountered.</p> + <p>End of file was encountered by the tokenizer.</p> </item> - <tag><c>{error, ErrorInfo, ErrorLine}</c></tag> + <tag><c>eof</c></tag> + <item> + <p>End of file was encountered by the I/O-server.</p> + </item> + <tag><c>{error, ErrorInfo, ErrorLocation}</c></tag> <item> - <p>An error occurred.</p> + <p>An error occurred while tokenizing.</p> </item> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> + <item> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> + if reading from an NFS file system.</p> + </item> </taglist> <p>Example:</p> <pre> @@ -840,13 +916,18 @@ enter><input>1.0er.</input> <name name="scan_erl_form" arity="1"/> <name name="scan_erl_form" arity="2"/> <name name="scan_erl_form" arity="3"/> + <name name="scan_erl_form" arity="4"/> + <type name="server_no_data"/> <fsummary>Read and tokenize an Erlang form</fsummary> <desc> <p>Reads data from the standard input (<c><anno>IoDevice</anno></c>), - prompting it with <c><anno>Prompt</anno></c>. Starts reading at line number - <c><anno>StartLine</anno></c> (1). The data is tokenized as if it were an + prompting it with <c><anno>Prompt</anno></c>. Starts reading + at location <c><anno>StartLocation</anno></c> (<c>1</c>). The + argument <c><anno>Options</anno></c> is passed on as the + <c>Options</c> argument of the <c>erl_scan:tokens/4</c> + function. The data is tokenized as if it were an Erlang form - one of the valid Erlang expressions in an - Erlang source file - until a final <c>'.'</c> is reached. + Erlang source file - until a final dot (<c>.</c>) is reached. This last token is also returned. The return values are the same as for <c>scan_erl_exprs/1,2,3</c> above.</p> </desc> @@ -855,27 +936,42 @@ enter><input>1.0er.</input> <name name="parse_erl_exprs" arity="1"/> <name name="parse_erl_exprs" arity="2"/> <name name="parse_erl_exprs" arity="3"/> + <name name="parse_erl_exprs" arity="4"/> <type name="parse_ret"/> + <type name="server_no_data"/> <fsummary>Read, tokenize and parse Erlang expressions</fsummary> <desc> - <p>Reads data from the standard input (<c><anno>IoDevice</anno></c>), - prompting it with <c><anno>Prompt</anno></c>. Starts reading at line number - <c><anno>StartLine</anno></c> (1). The data is tokenized and parsed as if - it were a sequence of Erlang expressions until a final '.' is - reached. It returns:</p> + <p>Reads data from the standard input + (<c><anno>IoDevice</anno></c>), prompting it with + <c><anno>Prompt</anno></c>. Starts reading at location + <c><anno>StartLocation</anno></c> (<c>1</c>). The argument + <c><anno>Options</anno></c> is passed on as the + <c>Options</c> argument of the <c>erl_scan:tokens/4</c> + function. The data is tokenized and parsed as if it were a + sequence of Erlang expressions until a final dot (<c>.</c>) is reached. + It returns:</p> <taglist> - <tag><c>{ok, ExprList, EndLine}</c></tag> + <tag><c>{ok, ExprList, EndLocation}</c></tag> <item> <p>The parsing was successful.</p> </item> - <tag><c>{eof, EndLine}</c></tag> + <tag><c>{eof, EndLocation}</c></tag> <item> - <p>End of file was encountered.</p> + <p>End of file was encountered by the tokenizer.</p> + </item> + <tag><c>eof</c></tag> + <item> + <p>End of file was encountered by the I/O-server.</p> </item> - <tag><c>{error, ErrorInfo, ErrorLine}</c></tag> + <tag><c>{error, ErrorInfo, ErrorLocation}</c></tag> <item> - <p>An error occurred.</p> + <p>An error occurred while tokenizing or parsing.</p> </item> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> + <item> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> + if reading from an NFS file system.</p> + </item> </taglist> <p>Example:</p> <pre> @@ -891,28 +987,42 @@ enter><input>abc("hey".</input> <name name="parse_erl_form" arity="1"/> <name name="parse_erl_form" arity="2"/> <name name="parse_erl_form" arity="3"/> + <name name="parse_erl_form" arity="4"/> <type name="parse_form_ret"/> + <type name="server_no_data"/> <fsummary>Read, tokenize and parse an Erlang form</fsummary> <desc> <p>Reads data from the standard input (<c><anno>IoDevice</anno></c>), - prompting it with <c><anno>Prompt</anno></c>. Starts reading at line number - <c><anno>StartLine</anno></c> (1). The data is tokenized and parsed as if + prompting it with <c><anno>Prompt</anno></c>. Starts reading at + location <c><anno>StartLocation</anno></c> (<c>1</c>). The argument + <c><anno>Options</anno></c> is passed on as the + <c>Options</c> argument of the <c>erl_scan:tokens/4</c> + function. The data is tokenized and parsed as if it were an Erlang form - one of the valid Erlang expressions - in an Erlang source file - until a final '.' is reached. It + in an Erlang source file - until a final dot (<c>.</c>) is reached. It returns:</p> <taglist> - <tag><c>{ok, AbsForm, EndLine}</c></tag> + <tag><c>{ok, AbsForm, EndLocation}</c></tag> <item> <p>The parsing was successful.</p> </item> - <tag><c>{eof, EndLine}</c></tag> + <tag><c>{eof, EndLocation}</c></tag> <item> - <p>End of file was encountered.</p> + <p>End of file was encountered by the tokenizer.</p> + </item> + <tag><c>eof</c></tag> + <item> + <p>End of file was encountered by the I/O-server.</p> </item> - <tag><c>{error, ErrorInfo, ErrorLine}</c></tag> + <tag><c>{error, ErrorInfo, ErrorLocation}</c></tag> <item> - <p>An error occurred.</p> + <p>An error occurred while tokenizing or parsing.</p> </item> + <tag><c>{error, <anno>ErrorDescription</anno>}</c></tag> + <item> + <p>Other (rare) error condition, for instance <c>{error, estale}</c> + if reading from an NFS file system.</p> + </item> </taglist> </desc> </func> @@ -940,7 +1050,7 @@ enter><input>bar.</input> </section> <section> <title>Standard Error</title> - <p>In certain situations, especially when the standard output is redirected, access to an io_server() specific for error messages might be convenient. The io_device 'standard_error' can be used to direct output to whatever the current operating system considers a suitable device for error output. Example on a Unix-like operating system:</p> + <p>In certain situations, especially when the standard output is redirected, access to an I/O-server specific for error messages might be convenient. The IO device <c>standard_error</c> can be used to direct output to whatever the current operating system considers a suitable IO device for error output. Example on a Unix-like operating system:</p> <pre> $ <input>erl -noshell -noinput -eval 'io:format(standard_error,"Error: ~s~n",["error 11"]),'\</input> <input>'init:stop().' > /dev/null</input> @@ -956,7 +1066,7 @@ Error: error 11</pre> <c>ErrorInfo</c> structure which is returned from all IO modules. It has the format:</p> <code type="none"> -{ErrorLine, Module, ErrorDescriptor}</code> +{ErrorLocation, Module, ErrorDescriptor}</code> <p>A string which describes the error is obtained with the following call:</p> <code type="none"> |