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<hr>
<h3 class="section" id="Controlling-Subprocesses-1"><span>36.5 Controlling Subprocesses<a class="copiable-link" href="#Controlling-Subprocesses-1"> ¶</a></span></h3>
<p>Octave includes some high-level commands like <code class="code">system</code> and
<code class="code">popen</code> for starting subprocesses. If you want to run another
program to perform some task and then look at its output, you will
probably want to use these functions.
</p>
<p>Octave also provides several very low-level Unix-like functions which
can also be used for starting subprocesses, but you should probably only
use them if you can’t find any way to do what you need with the
higher-level functions.
</p>
<a class="anchor" id="XREFsystem"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-system"><span><strong class="def-name">system</strong> <code class="def-code-arguments">("<var class="var">string</var>")</code><a class="copiable-link" href="#index-system"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-system-1"><span><strong class="def-name">system</strong> <code class="def-code-arguments">("<var class="var">string</var>", <var class="var">return_output</var>)</code><a class="copiable-link" href="#index-system-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-system-2"><span><strong class="def-name">system</strong> <code class="def-code-arguments">("<var class="var">string</var>", <var class="var">return_output</var>, <var class="var">type</var>)</code><a class="copiable-link" href="#index-system-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-system-3"><span><code class="def-type">[<var class="var">status</var>, <var class="var">output</var>] =</code> <strong class="def-name">system</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-system-3"> ¶</a></span></dt>
<dd><p>Execute a shell command specified by <var class="var">string</var>.
</p>
<p>If <var class="var">system</var> is called with one or more output arguments, or if the optional
argument <var class="var">return_output</var> is true and the subprocess is started
synchronously, then the output from the command is returned as a variable.
Otherwise, if the subprocess is executed synchronously, its output is sent to
the standard output. To send the output of a command executed with
<code class="code">system</code> through the pager, use a command like
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">[~, text] = system ("cmd");
more on;
disp (text);
</pre></div></div>
<p>or
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">more on;
printf ("%s\n", nthargout (2, "system", "cmd"));
</pre></div></div>
<p>If the optional argument <var class="var">type</var> is <code class="code">"async"</code>, the process is started
in the background and the process ID of the child process is returned
immediately. Otherwise, the child process is started and Octave waits until it
exits. If the <var class="var">type</var> argument is omitted, it defaults to the value
<code class="code">"sync"</code>.
</p>
<p>The <code class="code">system</code> function can return two values. The first is the exit status
of the command and the second is any output from the command that was written
to the standard output stream. For example,
</p>
<div class="example">
<pre class="example-preformatted">[status, output] = system ("echo foo & exit 2");
</pre></div>
<p>will set the variable <var class="var">output</var> to the string ‘<samp class="samp">foo</samp>’, and the variable
<var class="var">status</var> to the integer ‘<samp class="samp">2</samp>’.
</p>
<p>For commands run asynchronously, <var class="var">status</var> is the process id of the command
shell that is started to run the command.
</p>
<p>The shell used for executing commands varies with operating system and is
typically <samp class="file">/bin/sh</samp> for UNIX systems and <samp class="file">cmd.exe</samp> for
Windows systems.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFunix">unix</a>, <a class="ref" href="#XREFdos">dos</a>.
</p></dd></dl>
<a class="anchor" id="XREFunix"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-unix"><span><strong class="def-name">unix</strong> <code class="def-code-arguments">("<var class="var">command</var>")</code><a class="copiable-link" href="#index-unix"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-unix-1"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">unix</strong> <code class="def-code-arguments">("<var class="var">command</var>")</code><a class="copiable-link" href="#index-unix-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-unix-2"><span><code class="def-type">[<var class="var">status</var>, <var class="var">text</var>] =</code> <strong class="def-name">unix</strong> <code class="def-code-arguments">("<var class="var">command</var>")</code><a class="copiable-link" href="#index-unix-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-unix-3"><span><code class="def-type">[…] =</code> <strong class="def-name">unix</strong> <code class="def-code-arguments">("<var class="var">command</var>", "-echo")</code><a class="copiable-link" href="#index-unix-3"> ¶</a></span></dt>
<dd><p>Execute a system command if running under a Unix-like operating system,
otherwise do nothing.
</p>
<p>Octave waits for the external command to finish before returning the exit
status of the program in <var class="var">status</var> and any output in <var class="var">text</var>.
</p>
<p>When called with no output argument, or the <code class="code">"-echo"</code> argument is
given, then <var class="var">text</var> is also sent to standard output.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFdos">dos</a>, <a class="ref" href="#XREFsystem">system</a>, <a class="ref" href="System-Information.html#XREFisunix">isunix</a>, <a class="ref" href="System-Information.html#XREFismac">ismac</a>, <a class="ref" href="System-Information.html#XREFispc">ispc</a>.
</p></dd></dl>
<a class="anchor" id="XREFdos"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-dos"><span><strong class="def-name">dos</strong> <code class="def-code-arguments">("<var class="var">command</var>")</code><a class="copiable-link" href="#index-dos"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-dos-1"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">dos</strong> <code class="def-code-arguments">("<var class="var">command</var>")</code><a class="copiable-link" href="#index-dos-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-dos-2"><span><code class="def-type">[<var class="var">status</var>, <var class="var">text</var>] =</code> <strong class="def-name">dos</strong> <code class="def-code-arguments">("<var class="var">command"</var>)</code><a class="copiable-link" href="#index-dos-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-dos-3"><span><code class="def-type">[…] =</code> <strong class="def-name">dos</strong> <code class="def-code-arguments">("<var class="var">command</var>", "-echo")</code><a class="copiable-link" href="#index-dos-3"> ¶</a></span></dt>
<dd><p>Execute a system command if running under a Windows-like operating system,
otherwise do nothing.
</p>
<p>Octave waits for the external command to finish before returning the exit
status of the program in <var class="var">status</var> and any output in <var class="var">text</var>.
</p>
<p>When called with no output argument, or the <code class="code">"-echo"</code> argument is
given, then <var class="var">text</var> is also sent to standard output.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFunix">unix</a>, <a class="ref" href="#XREFsystem">system</a>, <a class="ref" href="System-Information.html#XREFisunix">isunix</a>, <a class="ref" href="System-Information.html#XREFismac">ismac</a>, <a class="ref" href="System-Information.html#XREFispc">ispc</a>.
</p></dd></dl>
<a class="anchor" id="XREFopen"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-open"><span><strong class="def-name">open</strong> <code class="def-code-arguments"><var class="var">file</var></code><a class="copiable-link" href="#index-open"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-open-1"><span><code class="def-type"><var class="var">output</var> =</code> <strong class="def-name">open</strong> <code class="def-code-arguments">(<var class="var">file</var>)</code><a class="copiable-link" href="#index-open-1"> ¶</a></span></dt>
<dd><p>Open the file <var class="var">file</var> in Octave or in an external application based on
the file type as determined by the filename extension.
</p>
<p>By default, recognized file types are
</p>
<dl class="table">
<dt><code class="code">.m</code></dt>
<dd><p>Open file in the editor. No <var class="var">output</var> value is returned.
</p>
</dd>
<dt><code class="code">.mat</code></dt>
<dt><code class="code">octave-workspace</code></dt>
<dd><p>Open the data file with <code class="code">load</code>. If no return value <var class="var">output</var>
is requested, variables are loaded in the base workspace. Otherwise
<var class="var">output</var> will be a structure containing loaded data.
See <a class="xref" href="Simple-File-I_002fO.html#XREFload">load function</a>.
</p>
</dd>
<dt><code class="code">.ofig</code></dt>
<dd><p>Open the figure with <code class="code">hgload</code>.
See <a class="xref" href="Printing-and-Saving-Plots.html#XREFhgload">hgload function</a>.
</p>
</dd>
<dt><code class="code">.fig, .ofig</code></dt>
<dd><p>Load the figure
</p>
</dd>
<dt><code class="code">.exe</code></dt>
<dd><p>Execute the program (on Windows systems only). No <var class="var">output</var> value
is returned.
</p></dd>
</dl>
<p>Custom file extensions may also be handled if a function <code class="code">openxxx</code>,
where <code class="code">xxx</code> is the extension, is found in the load path. The function
must accept the file name as input. For example, in order to load
<code class="code">".dat"</code> data files in the base workspace, as is done by
default for <code class="code">".mat"</code> files, one may define
<code class="code">"opendat.m"</code> with the following contents:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">function retval = opendat (fname)
evalin ("base", sprintf ("load ('%s');", fname));
endfunction
</pre></div></div>
<p>Other file types are opened in the appropriate external application.
</p></dd></dl>
<a class="anchor" id="XREFperl"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-perl"><span><code class="def-type"><var class="var">output</var> =</code> <strong class="def-name">perl</strong> <code class="def-code-arguments">(<var class="var">scriptfile</var>)</code><a class="copiable-link" href="#index-perl"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-perl-1"><span><code class="def-type"><var class="var">output</var> =</code> <strong class="def-name">perl</strong> <code class="def-code-arguments">(<var class="var">scriptfile</var>, <var class="var">argument1</var>, <var class="var">argument2</var>, …)</code><a class="copiable-link" href="#index-perl-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-perl-2"><span><code class="def-type">[<var class="var">output</var>, <var class="var">status</var>] =</code> <strong class="def-name">perl</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-perl-2"> ¶</a></span></dt>
<dd><p>Invoke Perl script <var class="var">scriptfile</var>, possibly with a list of command line
arguments.
</p>
<p>Return output in <var class="var">output</var> and optional status in <var class="var">status</var>. If
<var class="var">scriptfile</var> is not an absolute filename it is searched for in the
current directory and then in the Octave loadpath.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFsystem">system</a>, <a class="ref" href="#XREFpython">python</a>.
</p></dd></dl>
<a class="anchor" id="XREFpython"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-python"><span><code class="def-type"><var class="var">output</var> =</code> <strong class="def-name">python</strong> <code class="def-code-arguments">(<var class="var">scriptfile</var>)</code><a class="copiable-link" href="#index-python"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-python-1"><span><code class="def-type"><var class="var">output</var> =</code> <strong class="def-name">python</strong> <code class="def-code-arguments">(<var class="var">scriptfile</var>, <var class="var">argument1</var>, <var class="var">argument2</var>, …)</code><a class="copiable-link" href="#index-python-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-python-2"><span><code class="def-type">[<var class="var">output</var>, <var class="var">status</var>] =</code> <strong class="def-name">python</strong> <code class="def-code-arguments">(…)</code><a class="copiable-link" href="#index-python-2"> ¶</a></span></dt>
<dd><p>Invoke Python script <var class="var">scriptfile</var>, possibly with a list of command line
arguments.
</p>
<p>Return output in <var class="var">output</var> and optional status in <var class="var">status</var>. If
<var class="var">scriptfile</var> is not an absolute filename it is searched for in the
current directory and then in the Octave loadpath.
</p>
<p>Programming Note: On UNIX systems, the script will be executed by
<code class="command">python3</code> and on Windows by <code class="command">python</code>. You can override
these defaults by setting the <code class="env">PYTHON</code> environment variable, for example
from within Octave using <code class="code">setenv PYTHON /usr/local/bin/python3</code>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFsystem">system</a>, <a class="ref" href="#XREFperl">perl</a>.
</p></dd></dl>
<a class="anchor" id="XREFpopen"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-popen"><span><code class="def-type"><var class="var">fid</var> =</code> <strong class="def-name">popen</strong> <code class="def-code-arguments">(<var class="var">command</var>, <var class="var">mode</var>)</code><a class="copiable-link" href="#index-popen"> ¶</a></span></dt>
<dd><p>Start a process and create a pipe.
</p>
<p>The name of the command to run is given by <var class="var">command</var>. The argument
<var class="var">mode</var> may be
</p>
<dl class="table">
<dt><code class="code">"r"</code></dt>
<dd><p>The pipe will be connected to the standard output of the process, and
open for reading.
</p>
</dd>
<dt><code class="code">"w"</code></dt>
<dd><p>The pipe will be connected to the standard input of the process, and
open for writing.
</p></dd>
</dl>
<p>The file identifier corresponding to the input or output stream of the
process is returned in <var class="var">fid</var>.
</p>
<p>For example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">fid = popen ("ls -ltr / | tail -3", "r");
while (ischar (s = fgets (fid)))
fputs (stdout, s);
endwhile
-| drwxr-xr-x 33 root root 3072 Feb 15 13:28 etc
-| drwxr-xr-x 3 root root 1024 Feb 15 13:28 lib
-| drwxrwxrwt 15 root root 2048 Feb 17 14:53 tmp
</pre></div></div>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFpopen2">popen2</a>.
</p></dd></dl>
<a class="anchor" id="XREFpclose"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-pclose"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">pclose</strong> <code class="def-code-arguments">(<var class="var">fid</var>)</code><a class="copiable-link" href="#index-pclose"> ¶</a></span></dt>
<dd><p>Close a file identifier <var class="var">fid</var> that was opened by <code class="code">popen</code>.
</p>
<p>If successful, <code class="code">fclose</code> returns 0, otherwise, it returns -1.
</p>
<p>Programming Note: The function <code class="code">fclose</code> may also be used for the same
purpose.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Opening-and-Closing-Files.html#XREFfclose">fclose</a>, <a class="ref" href="#XREFpopen">popen</a>.
</p></dd></dl>
<a class="anchor" id="XREFpopen2"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-popen2"><span><code class="def-type">[<var class="var">in</var>, <var class="var">out</var>, <var class="var">pid</var>] =</code> <strong class="def-name">popen2</strong> <code class="def-code-arguments">(<var class="var">command</var>, <var class="var">args</var>)</code><a class="copiable-link" href="#index-popen2"> ¶</a></span></dt>
<dd><p>Start a subprocess with two-way communication.
</p>
<p>The name of the process is given by <var class="var">command</var>, and <var class="var">args</var> is an
array or cell array of strings containing options for the command.
</p>
<p>The file identifiers for the input and output streams of the subprocess are
returned in <var class="var">in</var> and <var class="var">out</var>. If execution of the command is
successful, <var class="var">pid</var> contains the process ID of the subprocess. Otherwise,
<var class="var">pid</var> is −1.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example-preformatted">[in, out, pid] = popen2 ("sort", "-r");
fputs (in, "these\nare\nsome\nstrings\n");
fclose (in);
EAGAIN = errno ("EAGAIN");
done = false;
do
s = fgets (out);
if (ischar (s))
fputs (stdout, s);
elseif (errno () == EAGAIN)
pause (0.1);
fclear (out);
else
done = true;
endif
until (done)
fclose (out);
waitpid (pid);
-| these
-| strings
-| some
-| are
</pre></div>
<p>Note that <code class="code">popen2</code>, unlike <code class="code">popen</code>, will not "reap"
the child process. If you don’t use <code class="code">waitpid</code> to check the child’s
exit status, it will linger until Octave exits.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFpopen">popen</a>, <a class="ref" href="#XREFwaitpid">waitpid</a>.
</p></dd></dl>
<a class="anchor" id="XREFEXEC_005fPATH"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-EXEC_005fPATH"><span><code class="def-type"><var class="var">val</var> =</code> <strong class="def-name">EXEC_PATH</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-EXEC_005fPATH"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-EXEC_005fPATH-1"><span><code class="def-type"><var class="var">old_val</var> =</code> <strong class="def-name">EXEC_PATH</strong> <code class="def-code-arguments">(<var class="var">new_val</var>)</code><a class="copiable-link" href="#index-EXEC_005fPATH-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-EXEC_005fPATH-2"><span><code class="def-type"><var class="var">old_val</var> =</code> <strong class="def-name">EXEC_PATH</strong> <code class="def-code-arguments">(<var class="var">new_val</var>, "local")</code><a class="copiable-link" href="#index-EXEC_005fPATH-2"> ¶</a></span></dt>
<dd><p>Query or set the internal variable that specifies a colon separated
list of directories to append to the shell PATH when executing external
programs.
</p>
<p>The initial value of is taken from the environment variable
<code class="env">OCTAVE_EXEC_PATH</code><!-- /@w -->, but that value can be overridden by the command
line argument <samp class="option">--exec-path PATH</samp>.
</p>
<p>When called from inside a function with the <code class="code">"local"</code> option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Loading-and-Saving-Images.html#XREFIMAGE_005fPATH">IMAGE_PATH</a>, <a class="ref" href="System-Information.html#XREFOCTAVE_005fHOME">OCTAVE_HOME</a>, <a class="ref" href="System-Information.html#XREFOCTAVE_005fEXEC_005fHOME">OCTAVE_EXEC_HOME</a>.
</p></dd></dl>
<p>In most cases, the following functions simply decode their arguments and
make the corresponding Unix system calls. For a complete example of how
they can be used, look at the definition of the function <code class="code">popen2</code>.
</p>
<a class="anchor" id="XREFfork"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-fork"><span><code class="def-type">[<var class="var">pid</var>, <var class="var">msg</var>] =</code> <strong class="def-name">fork</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-fork"> ¶</a></span></dt>
<dd><p>Create a copy of the current process.
</p>
<p>Fork can return one of the following values:
</p>
<dl class="table">
<dt>> 0</dt>
<dd><p>You are in the parent process. The value returned from <code class="code">fork</code> is the
process id of the child process. You should probably arrange to wait for
any child processes to exit.
</p>
</dd>
<dt>0</dt>
<dd><p>You are in the child process. You can call <code class="code">exec</code> to start another
process. If that fails, you should probably call <code class="code">exit</code>.
</p>
</dd>
<dt>< 0</dt>
<dd><p>The call to <code class="code">fork</code> failed for some reason. You must take evasive
action. A system dependent error message will be waiting in <var class="var">msg</var>.
</p></dd>
</dl>
</dd></dl>
<a class="anchor" id="XREFexec"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-exec"><span><code class="def-type">[<var class="var">err</var>, <var class="var">msg</var>] =</code> <strong class="def-name">exec</strong> <code class="def-code-arguments">(<var class="var">file</var>, <var class="var">args</var>)</code><a class="copiable-link" href="#index-exec"> ¶</a></span></dt>
<dd><p>Replace current process with a new process.
</p>
<p>Calling <code class="code">exec</code> without first calling <code class="code">fork</code> will terminate your
current Octave process and replace it with the program named by <var class="var">file</var>.
For example,
</p>
<div class="example">
<pre class="example-preformatted">exec ("ls", "-l")
</pre></div>
<p>will run <code class="code">ls</code> and return you to your shell prompt.
</p>
<p>If successful, <code class="code">exec</code> does not return. If <code class="code">exec</code> does return,
<var class="var">err</var> will be nonzero, and <var class="var">msg</var> will contain a system-dependent
error message.
</p></dd></dl>
<a class="anchor" id="XREFpipe"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-pipe"><span><code class="def-type">[<var class="var">read_fd</var>, <var class="var">write_fd</var>, <var class="var">err</var>, <var class="var">msg</var>] =</code> <strong class="def-name">pipe</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-pipe"> ¶</a></span></dt>
<dd><p>Create a pipe and return the reading and writing ends of the pipe into
<var class="var">read_fd</var> and <var class="var">write_fd</var> respectively.
</p>
<p>If successful, <var class="var">err</var> is 0 and <var class="var">msg</var> is an empty string.
Otherwise, <var class="var">err</var> is nonzero and <var class="var">msg</var> contains a system-dependent
error message.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Filesystem-Utilities.html#XREFmkfifo">mkfifo</a>.
</p></dd></dl>
<a class="anchor" id="XREFdup2"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-dup2"><span><code class="def-type">[<var class="var">fid</var>, <var class="var">msg</var>] =</code> <strong class="def-name">dup2</strong> <code class="def-code-arguments">(<var class="var">old</var>, <var class="var">new</var>)</code><a class="copiable-link" href="#index-dup2"> ¶</a></span></dt>
<dd><p>Duplicate a file descriptor.
</p>
<p>If successful, <var class="var">fid</var> is greater than zero and contains the new file ID.
Otherwise, <var class="var">fid</var> is negative and <var class="var">msg</var> contains a system-dependent
error message.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>, <a class="ref" href="Opening-and-Closing-Files.html#XREFfclose">fclose</a>, <a class="ref" href="#XREFfcntl">fcntl</a>.
</p></dd></dl>
<a class="anchor" id="XREFwaitpid"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-waitpid"><span><code class="def-type">[<var class="var">pid</var>, <var class="var">status</var>, <var class="var">msg</var>] =</code> <strong class="def-name">waitpid</strong> <code class="def-code-arguments">(<var class="var">pid</var>, <var class="var">options</var>)</code><a class="copiable-link" href="#index-waitpid"> ¶</a></span></dt>
<dd><p>Wait for process <var class="var">pid</var> to terminate.
</p>
<p>The <var class="var">pid</var> argument can be:
</p>
<dl class="table">
<dt>−1</dt>
<dd><p>Wait for any child process.
</p>
</dd>
<dt>0</dt>
<dd><p>Wait for any child process whose process group ID is equal to that of the
Octave interpreter process.
</p>
</dd>
<dt>> 0</dt>
<dd><p>Wait for termination of the child process with ID <var class="var">pid</var>.
</p></dd>
</dl>
<p>The <var class="var">options</var> argument can be a bitwise OR of zero or more of the
following constants:
</p>
<dl class="table">
<dt><code class="code">0</code></dt>
<dd><p>Wait until signal is received or a child process exits (this is the default
if the <var class="var">options</var> argument is missing).
</p>
</dd>
<dt><code class="code">WNOHANG</code></dt>
<dd><p>Do not hang if status is not immediately available.
</p>
</dd>
<dt><code class="code">WUNTRACED</code></dt>
<dd><p>Report the status of any child processes that are stopped, and whose status
has not yet been reported since they stopped.
</p>
</dd>
<dt><code class="code">WCONTINUE</code></dt>
<dd><p>Return if a stopped child has been resumed by delivery of <code class="code">SIGCONT</code>.
This value may not be meaningful on all systems.
</p></dd>
</dl>
<p>If the returned value of <var class="var">pid</var> is greater than 0, it is the process ID
of the child process that exited. If an error occurs, <var class="var">pid</var> will be
less than zero and <var class="var">msg</var> will contain a system-dependent error message.
The value of <var class="var">status</var> contains additional system-dependent information
about the subprocess that exited.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFWCONTINUE">WCONTINUE</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWNOHANG">WNOHANG</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWUNTRACED">WUNTRACED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWCONTINUE"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WCONTINUE"><span><code class="def-type"><var class="var">v</var> =</code> <strong class="def-name">WCONTINUE</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-WCONTINUE"> ¶</a></span></dt>
<dd><p>Return the numerical value of the <code class="code">WCONTINUE</code> macro.
</p>
<p><code class="code">WCONTINUE</code> is the option argument that may be passed to
<code class="code">waitpid</code> to indicate that it should also return if a stopped child
has been resumed by delivery of a <code class="code">SIGCONT</code> signal.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWNOHANG">WNOHANG</a>, <a class="ref" href="#XREFWUNTRACED">WUNTRACED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWCOREDUMP"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WCOREDUMP"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WCOREDUMP</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WCOREDUMP"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
true if the child produced a core dump.
</p>
<p>This function should only be employed if <code class="code">WIFSIGNALED</code> returned true.
The macro used to implement this function is not specified in POSIX.1-2001
and is not available on some Unix implementations (e.g., AIX, SunOS).
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWEXITSTATUS"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WEXITSTATUS"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WEXITSTATUS</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WEXITSTATUS"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
the exit status of the child.
</p>
<p>This function should only be employed if <code class="code">WIFEXITED</code> returned true.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWIFCONTINUED"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WIFCONTINUED"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WIFCONTINUED</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WIFCONTINUED"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
true if the child process was resumed by delivery of <code class="code">SIGCONT</code>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>.
</p></dd></dl>
<a class="anchor" id="XREFWIFSIGNALED"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WIFSIGNALED"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WIFSIGNALED</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WIFSIGNALED"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
true if the child process was terminated by a signal.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWIFSTOPPED"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WIFSTOPPED"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WIFSTOPPED</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WIFSTOPPED"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
true if the child process was stopped by delivery of a signal.
</p>
<p>This is only possible if the call was done using <code class="code">WUNTRACED</code> or when
the child is being traced (see ptrace(2)).
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWIFEXITED"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WIFEXITED"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WIFEXITED</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WIFEXITED"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
true if the child terminated normally.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWNOHANG"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WNOHANG"><span><code class="def-type"><var class="var">v</var> =</code> <strong class="def-name">WNOHANG</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-WNOHANG"> ¶</a></span></dt>
<dd><p>Return the numerical value of the <code class="code">WNOHANG</code> macro.
</p>
<p><code class="code">WNOHANG</code> is the option argument that may be passed to
<code class="code">waitpid</code> to indicate that it should return its status immediately
instead of waiting for a process to exit.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWUNTRACED">WUNTRACED</a>, <a class="ref" href="#XREFWCONTINUE">WCONTINUE</a>.
</p></dd></dl>
<a class="anchor" id="XREFWSTOPSIG"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WSTOPSIG"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WSTOPSIG</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WSTOPSIG"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
the number of the signal which caused the child to stop.
</p>
<p>This function should only be employed if <code class="code">WIFSTOPPED</code> returned true.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWTERMSIG">WTERMSIG</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWTERMSIG"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WTERMSIG"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">WTERMSIG</strong> <code class="def-code-arguments">(<var class="var">status</var>)</code><a class="copiable-link" href="#index-WTERMSIG"> ¶</a></span></dt>
<dd><p>Given <var class="var">status</var> from a call to <code class="code">waitpid</code>, return
the number of the signal that caused the child process to terminate.
</p>
<p>This function should only be employed if <code class="code">WIFSIGNALED</code> returned true.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWIFEXITED">WIFEXITED</a>, <a class="ref" href="#XREFWEXITSTATUS">WEXITSTATUS</a>, <a class="ref" href="#XREFWIFSIGNALED">WIFSIGNALED</a>, <a class="ref" href="#XREFWCOREDUMP">WCOREDUMP</a>, <a class="ref" href="#XREFWIFSTOPPED">WIFSTOPPED</a>, <a class="ref" href="#XREFWSTOPSIG">WSTOPSIG</a>, <a class="ref" href="#XREFWIFCONTINUED">WIFCONTINUED</a>.
</p></dd></dl>
<a class="anchor" id="XREFWUNTRACED"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-WUNTRACED"><span><code class="def-type"><var class="var">v</var> =</code> <strong class="def-name">WUNTRACED</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-WUNTRACED"> ¶</a></span></dt>
<dd><p>Return the numerical value of the <code class="code">WUNTRACED</code> macro.
</p>
<p><code class="code">WUNTRACED</code> is the option argument that may be passed to
<code class="code">waitpid</code> to indicate that it should also return if the child
process has stopped but is not traced via the <code class="code">ptrace</code> system call
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFwaitpid">waitpid</a>, <a class="ref" href="#XREFWNOHANG">WNOHANG</a>, <a class="ref" href="#XREFWCONTINUE">WCONTINUE</a>.
</p></dd></dl>
<a class="anchor" id="XREFfcntl"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-fcntl"><span><strong class="def-name">fcntl</strong> <code class="def-code-arguments">(<var class="var">fid</var>, <var class="var">request</var>, <var class="var">arg</var>)</code><a class="copiable-link" href="#index-fcntl"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-fcntl-1"><span><code class="def-type">[<var class="var">status</var>, <var class="var">msg</var>] =</code> <strong class="def-name">fcntl</strong> <code class="def-code-arguments">(<var class="var">fid</var>, <var class="var">request</var>, <var class="var">arg</var>)</code><a class="copiable-link" href="#index-fcntl-1"> ¶</a></span></dt>
<dd><p>Change the properties of the open file <var class="var">fid</var>.
</p>
<p>The following values may be passed as <var class="var">request</var>:
</p>
<dl class="vtable">
<dt><a id="index-F_005fDUPFD"></a><span><code class="code">F_DUPFD</code><a class="copiable-link" href="#index-F_005fDUPFD"> ¶</a></span></dt>
<dd><p>Return a duplicate file descriptor.
</p>
</dd>
<dt><a id="index-F_005fGETFD"></a><span><code class="code">F_GETFD</code><a class="copiable-link" href="#index-F_005fGETFD"> ¶</a></span></dt>
<dd><p>Return the file descriptor flags for <var class="var">fid</var>.
</p>
</dd>
<dt><a id="index-F_005fSETFD"></a><span><code class="code">F_SETFD</code><a class="copiable-link" href="#index-F_005fSETFD"> ¶</a></span></dt>
<dd><p>Set the file descriptor flags for <var class="var">fid</var>.
</p>
</dd>
<dt><a id="index-F_005fGETFL"></a><span><code class="code">F_GETFL</code><a class="copiable-link" href="#index-F_005fGETFL"> ¶</a></span></dt>
<dd><p>Return the file status flags for <var class="var">fid</var>. The following codes may be
returned (some of the flags may be undefined on some systems).
</p>
<dl class="vtable">
<dt><a id="index-O_005fRDONLY"></a><span><code class="code">O_RDONLY</code><a class="copiable-link" href="#index-O_005fRDONLY"> ¶</a></span></dt>
<dd><p>Open for reading only.
</p>
</dd>
<dt><a id="index-O_005fWRONLY"></a><span><code class="code">O_WRONLY</code><a class="copiable-link" href="#index-O_005fWRONLY"> ¶</a></span></dt>
<dd><p>Open for writing only.
</p>
</dd>
<dt><a id="index-O_005fRDWR"></a><span><code class="code">O_RDWR</code><a class="copiable-link" href="#index-O_005fRDWR"> ¶</a></span></dt>
<dd><p>Open for reading and writing.
</p>
</dd>
<dt><a id="index-O_005fAPPEND"></a><span><code class="code">O_APPEND</code><a class="copiable-link" href="#index-O_005fAPPEND"> ¶</a></span></dt>
<dd><p>Append on each write.
</p>
</dd>
<dt><a id="index-O_005fCREAT"></a><span><code class="code">O_CREAT</code><a class="copiable-link" href="#index-O_005fCREAT"> ¶</a></span></dt>
<dd><p>Create the file if it does not exist.
</p>
</dd>
<dt><a id="index-O_005fNONBLOCK"></a><span><code class="code">O_NONBLOCK</code><a class="copiable-link" href="#index-O_005fNONBLOCK"> ¶</a></span></dt>
<dd><p>Non-blocking mode.
</p>
</dd>
<dt><a id="index-O_005fSYNC"></a><span><code class="code">O_SYNC</code><a class="copiable-link" href="#index-O_005fSYNC"> ¶</a></span></dt>
<dd><p>Wait for writes to complete.
</p>
</dd>
<dt><a id="index-O_005fASYNC"></a><span><code class="code">O_ASYNC</code><a class="copiable-link" href="#index-O_005fASYNC"> ¶</a></span></dt>
<dd><p>Asynchronous I/O.
</p></dd>
</dl>
</dd>
<dt><a id="index-F_005fSETFL"></a><span><code class="code">F_SETFL</code><a class="copiable-link" href="#index-F_005fSETFL"> ¶</a></span></dt>
<dd><p>Set the file status flags for <var class="var">fid</var> to the value specified by <var class="var">arg</var>.
The only flags that can be changed are <code class="code">O_APPEND</code><!-- /@w --> and
<code class="code">O_NONBLOCK</code><!-- /@w -->.
</p></dd>
</dl>
<p>If successful, <var class="var">status</var> is 0 and <var class="var">msg</var> is an empty string. Otherwise,
<var class="var">status</var> is -1 and <var class="var">msg</var> contains a system-dependent error
message.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>, <a class="ref" href="#XREFdup2">dup2</a>.
</p></dd></dl>
<a class="anchor" id="XREFkill"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-kill"><span><strong class="def-name">kill</strong> <code class="def-code-arguments">(<var class="var">pid</var>, <var class="var">sig</var>)</code><a class="copiable-link" href="#index-kill"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-kill-1"><span><code class="def-type">[<var class="var">status</var>, <var class="var">msg</var>] =</code> <strong class="def-name">kill</strong> <code class="def-code-arguments">(<var class="var">pid</var>, <var class="var">sig</var>)</code><a class="copiable-link" href="#index-kill-1"> ¶</a></span></dt>
<dd><p>Send signal <var class="var">sig</var> to process <var class="var">pid</var>.
</p>
<p>If <var class="var">pid</var> is positive, then signal <var class="var">sig</var> is sent to <var class="var">pid</var>.
</p>
<p>If <var class="var">pid</var> is 0, then signal <var class="var">sig</var> is sent to every process in the
process group of the current process.
</p>
<p>If <var class="var">pid</var> is -1, then signal <var class="var">sig</var> is sent to every process except
process 1.
</p>
<p>If <var class="var">pid</var> is less than -1, then signal <var class="var">sig</var> is sent to every process in
the process group <var class="var">-pid</var>.
</p>
<p>If <var class="var">sig</var> is 0, then no signal is sent, but error checking is still
performed.
</p>
<p>If successful, <var class="var">status</var> is 0 and <var class="var">msg</var> is an empty string.
Otherwise, <var class="var">status</var> is -1 and <var class="var">msg</var> contains a system-dependent
error message.
</p></dd></dl>
<a class="anchor" id="XREFSIG"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-SIG"><span><code class="def-type"><var class="var">S</var> =</code> <strong class="def-name">SIG</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-SIG"> ¶</a></span></dt>
<dd><p>Return a structure containing Unix signal names and their defined values.
</p></dd></dl>
</div>
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