1<html lang="en"> 2<head> 3<title>system - Untitled</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Untitled"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Stdlib.html#Stdlib" title="Stdlib"> 9<link rel="prev" href="wcstoull.html#wcstoull" title="wcstoull"> 10<link rel="next" href="wcstombs.html#wcstombs" title="wcstombs"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<meta http-equiv="Content-Style-Type" content="text/css"> 13<style type="text/css"><!-- 14 pre.display { font-family:inherit } 15 pre.format { font-family:inherit } 16 pre.smalldisplay { font-family:inherit; font-size:smaller } 17 pre.smallformat { font-family:inherit; font-size:smaller } 18 pre.smallexample { font-size:smaller } 19 pre.smalllisp { font-size:smaller } 20 span.sc { font-variant:small-caps } 21 span.roman { font-family:serif; font-weight:normal; } 22 span.sansserif { font-family:sans-serif; font-weight:normal; } 23--></style> 24<link rel="stylesheet" type="text/css" href="../cs.css"> 25</head> 26<body> 27<div class="node"> 28<a name="system"></a> 29<p> 30Next: <a rel="next" accesskey="n" href="wcstombs.html#wcstombs">wcstombs</a>, 31Previous: <a rel="previous" accesskey="p" href="wcstoull.html#wcstoull">wcstoull</a>, 32Up: <a rel="up" accesskey="u" href="Stdlib.html#Stdlib">Stdlib</a> 33<hr> 34</div> 35 36<h3 class="section">2.45 <code>system</code>—execute command string</h3> 37 38<p><a name="index-system-106"></a><a name="index-g_t_005fsystem_005fr-107"></a><strong>Synopsis</strong> 39<pre class="example"> #include <stdlib.h> 40 int system(char *<var>s</var>); 41 42 int _system_r(void *<var>reent</var>, char *<var>s</var>); 43 44</pre> 45 <p><strong>Description</strong><br> 46 47 <p>Use <code>system</code> to pass a command string <code>*</code><var>s</var> to <code>/bin/sh</code> on 48your system, and wait for it to finish executing. 49 50 <p>Use “<code>system(NULL)</code>” to test whether your system has <code>/bin/sh</code> 51available. 52 53 <p>The alternate function <code>_system_r</code> is a reentrant version. The 54extra argument <var>reent</var> is a pointer to a reentrancy structure. 55 56 <p><br> 57<strong>Returns</strong><br> 58<code>system(NULL)</code> returns a non-zero value if <code>/bin/sh</code> is available, and 59<code>0</code> if it is not. 60 61 <p>With a command argument, the result of <code>system</code> is the exit status 62returned by <code>/bin/sh</code>. 63 64 <p><br> 65<strong>Portability</strong><br> 66ANSI C requires <code>system</code>, but leaves the nature and effects of a 67command processor undefined. ANSI C does, however, specify that 68<code>system(NULL)</code> return zero or nonzero to report on the existence of 69a command processor. 70 71 <p>POSIX.2 requires <code>system</code>, and requires that it invoke a <code>sh</code>. 72Where <code>sh</code> is found is left unspecified. 73 74 <p>Supporting OS subroutines required: <code>_exit</code>, <code>_execve</code>, <code>_fork_r</code>, 75<code>_wait_r</code>. 76 77 <p><br> 78 79 </body></html> 80 81