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108 lines
4.2 KiB
HTML
108 lines
4.2 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<title>system (The Red Hat newlib C Library)</title>
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<meta name="description" content="system (The Red Hat newlib C Library)">
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<link href="Document-Index.html#Document-Index" rel="index" title="Document Index">
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<link href="Document-Index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Stdlib.html#Stdlib" rel="up" title="Stdlib">
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<body lang="en">
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<a name="system"></a>
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<div class="header">
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<p>
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Next: <a href="utoa.html#utoa" accesskey="n" rel="next">utoa</a>, Previous: <a href="wcstoull.html#wcstoull" accesskey="p" rel="prev">wcstoull</a>, Up: <a href="Stdlib.html#Stdlib" accesskey="u" rel="up">Stdlib</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="system_002d_002d_002dexecute-command-string"></a>
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<h3 class="section">2.48 <code>system</code>—execute command string</h3>
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<a name="index-system"></a>
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<a name="index-_005fsystem_005fr"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <stdlib.h>
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int system(char *<var>s</var>);
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int _system_r(void *<var>reent</var>, char *<var>s</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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</p>
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<p>Use <code>system</code> to pass a command string <code>*<var>s</var></code> to <code>/bin/sh</code> on
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your system, and wait for it to finish executing.
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</p>
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<p>Use “<code>system(NULL)</code>” to test whether your system has <code>/bin/sh</code>
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available.
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</p>
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<p>The alternate function <code>_system_r</code> is a reentrant version. The
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extra argument <var>reent</var> is a pointer to a reentrancy structure.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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<code>system(NULL)</code> returns a non-zero value if <code>/bin/sh</code> is available, and
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<code>0</code> if it is not.
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</p>
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<p>With a command argument, the result of <code>system</code> is the exit status
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returned by <code>/bin/sh</code>.
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</p>
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<br>
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<p><strong>Portability</strong><br>
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ANSI C requires <code>system</code>, but leaves the nature and effects of a
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command processor undefined. ANSI C does, however, specify that
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<code>system(NULL)</code> return zero or nonzero to report on the existence of
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a command processor.
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</p>
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<p>POSIX.2 requires <code>system</code>, and requires that it invoke a <code>sh</code>.
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Where <code>sh</code> is found is left unspecified.
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</p>
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<p>Supporting OS subroutines required: <code>_exit</code>, <code>_execve</code>, <code>_fork_r</code>,
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<code>_wait_r</code>.
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</p>
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<br>
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