diff options
Diffstat (limited to 'lib/kernel/doc')
| -rw-r--r-- | lib/kernel/doc/src/file.xml | 14 | ||||
| -rw-r--r-- | lib/kernel/doc/src/os.xml | 61 | ||||
| -rw-r--r-- | lib/kernel/doc/src/pg2.xml | 10 |
3 files changed, 66 insertions, 19 deletions
diff --git a/lib/kernel/doc/src/file.xml b/lib/kernel/doc/src/file.xml index dcb9640dcf..338d62e82b 100644 --- a/lib/kernel/doc/src/file.xml +++ b/lib/kernel/doc/src/file.xml @@ -1693,9 +1693,9 @@ <desc> <p>Makes sure that any buffers kept by the operating system (not by the Erlang runtime system) are written to disk. In - many ways it's resembles fsync but it not requires to update - some of file's metadata such as the access time. On - some platforms, this function might have no effect.</p> + many ways it resembles fsync but it does not update + some of the file's metadata such as the access time. On + some platforms this function has no effect.</p> <p>Applications that access databases or log files often write a tiny data fragment (e.g., one line in a log file) and then call fsync() immediately in order to ensure that the written @@ -1703,11 +1703,11 @@ will always initiate two write operations: one for the newly written data and another one in order to update the modification time stored in the inode. If the modification time is not a part - of the transaction concept fdatasync() can be used to avoid + of the transaction concept, fdatasync() can be used to avoid unnecessary inode disk write operations.</p> - <p>Available only in some POSIX systems. This call results in a - call to fsync(), or has no effect, in systems not implementing - the fdatasync syscall.</p> + <p>Available only in some POSIX systems, this call results in a + call to fsync(), or has no effect in systems not implementing + the fdatasync() syscall.</p> </desc> </func> <func> diff --git a/lib/kernel/doc/src/os.xml b/lib/kernel/doc/src/os.xml index 2b57e75023..b9dbede0d3 100644 --- a/lib/kernel/doc/src/os.xml +++ b/lib/kernel/doc/src/os.xml @@ -100,6 +100,19 @@ DirOut = os:cmd("dir"), % on Win32 platform</code> </desc> </func> <func> + <name name="getenv" arity="2"/> + <fsummary>Get the value of an environment variable</fsummary> + <desc> + <p>Returns the <c><anno>Value</anno></c> of the environment variable + <c><anno>VarName</anno></c>, or <c>DefaultValue</c> if the environment variable + is undefined.</p> + <p>If Unicode file name encoding is in effect (see the <seealso + marker="erts:erl#file_name_encoding">erl manual + page</seealso>), the strings (both <c><anno>VarName</anno></c> and + <c><anno>Value</anno></c>) may contain characters with codepoints > 255.</p> + </desc> + </func> + <func> <name name="getpid" arity="0"/> <fsummary>Return the process identifier of the emulator process</fsummary> <desc> @@ -129,14 +142,49 @@ DirOut = os:cmd("dir"), % on Win32 platform</code> </desc> </func> <func> + <name name="system_time" arity="0"/> + <fsummary>Current OS system time</fsummary> + <desc> + <p>Returns current + <seealso marker="erts:time_correction#OS_System_Time">OS system time</seealso> + in <c>native</c> + <seealso marker="erts:erlang#type_time_unit">time unit</seealso>.</p> + + <note><p>This time is <em>not</em> a monotonically increasing time.</p></note> + </desc> + </func> + <func> + <name name="system_time" arity="1"/> + <fsummary>Current OS system time</fsummary> + <desc> + <p>Returns current + <seealso marker="erts:time_correction#OS_System_Time">OS system time</seealso> + converted into the <c><anno>Unit</anno></c> passed as argument.</p> + + <p>Calling <c>os:system_time(<anno>Unit</anno>)</c> is equivalent to: + <seealso marker="erts:erlang#convert_time_unit/3"><c>erlang:convert_time_unit</c></seealso><c>(</c><seealso marker="#system_time/0"><c>os:system_time()</c></seealso><c>, + native, <anno>Unit</anno>)</c>.</p> + + <note><p>This time is <em>not</em> a monotonically increasing time.</p></note> + </desc> + </func> + <func> <name name="timestamp" arity="0"/> <type_desc variable="Timestamp">Timestamp = {MegaSecs, Secs, MicroSecs}</type_desc> - <fsummary>Returna a timestamp from the OS in the erlang:now/0 format</fsummary> + <fsummary>Current OS system time on the erlang:timestamp/0 format</fsummary> <desc> - <p>Returns a tuple in the same format as <seealso marker="erts:erlang#now/0">erlang:now/0</seealso>. The difference is that this function returns what the operating system thinks (a.k.a. the wall clock time) without any attempts at time correction. The result of two different calls to this function is <em>not</em> guaranteed to be different.</p> - <p>The most obvious use for this function is logging. The tuple can be used together with the function <seealso marker="stdlib:calendar#now_to_universal_time/1">calendar:now_to_universal_time/1</seealso> -or <seealso marker="stdlib:calendar#now_to_local_time/1">calendar:now_to_local_time/1</seealso> to get calendar time. Using the calendar time together with the <c>MicroSecs</c> part of the return tuple from this function allows you to log timestamps in high resolution and consistent with the time in the rest of the operating system.</p> - <p>Example of code formatting a string in the format "DD Mon YYYY HH:MM:SS.mmmmmm", where DD is the day of month, Mon is the textual month name, YYYY is the year, HH:MM:SS is the time and mmmmmm is the microseconds in six positions:</p> + <p>Returns current + <seealso marker="erts:time_correction#OS_System_Time">OS system time</seealso> + in the same format as <seealso marker="erts:erlang#timestamp/0">erlang:timestamp/0</seealso>. + The tuple can be used together with the function + <seealso marker="stdlib:calendar#now_to_universal_time/1">calendar:now_to_universal_time/1</seealso> + or <seealso marker="stdlib:calendar#now_to_local_time/1">calendar:now_to_local_time/1</seealso> to + get calendar time. Using the calendar time together with the <c>MicroSecs</c> part of the return + tuple from this function allows you to log timestamps in high resolution and consistent with the + time in the rest of the operating system.</p> + <p>Example of code formatting a string in the format "DD Mon YYYY HH:MM:SS.mmmmmm", where + DD is the day of month, Mon is the textual month name, YYYY is the year, HH:MM:SS is the time and + mmmmmm is the microseconds in six positions:</p> <code> -module(print_time). -export([format_utc_timestamp/0]). @@ -155,6 +203,9 @@ format_utc_timestamp() -> 1> <input>io:format("~s~n",[print_time:format_utc_timestamp()]).</input> 29 Apr 2009 9:55:30.051711 </pre> + <p>OS system time can also be retreived by + <c><seealso marker="#system_time/0"><c>os:system_time/0</c></seealso></c>, + and <seealso marker="#system_time/1"><c>os:system_time/1</c></seealso>.</p> </desc> </func> <func> diff --git a/lib/kernel/doc/src/pg2.xml b/lib/kernel/doc/src/pg2.xml index 5eb63c1ef6..35cf85470a 100644 --- a/lib/kernel/doc/src/pg2.xml +++ b/lib/kernel/doc/src/pg2.xml @@ -34,11 +34,8 @@ <module>pg2</module> <modulesummary>Distributed Named Process Groups</modulesummary> <description> - <p>This module implements process groups. The groups in this - module differ from the groups in the module <c>pg</c> in several - ways. In <c>pg</c>, each message is sent to all members in the - group. In this module, each message may be sent to one, some, or - all members. + <p>This module implements process groups. Each message may be sent + to one, some, or all members of the group. </p> <p>A group of processes can be accessed by a common name. For example, if there is a group named <c>foobar</c>, there can be a @@ -160,8 +157,7 @@ <section> <title>See Also</title> - <p><seealso marker="kernel_app">kernel(6)</seealso>, - <seealso marker="stdlib:pg">pg(3)</seealso></p> + <p><seealso marker="kernel_app">kernel(6)</seealso></p> </section> </erlref> |