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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>putenv</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_1768"> </a>NAME</h4><blockquote>putenv - change or add a value to environment</blockquote><h4><a name = "tag_000_007_1769"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="stdlib.h.html">stdlib.h</a>>int putenv(char *<i>string</i>);</code></pre></blockquote><h4><a name = "tag_000_007_1770"> </a>DESCRIPTION</h4><blockquote>The<i>putenv()</i>function uses the<i>string</i>argument to set environment variable values. The<i>string</i>argument should point to a string of the form "<i>name</i>=<i>value</i>".The<i>putenv()</i>function makes the value of the environment variable<i>name</i>equal to<i>value</i>by altering an existing variable or creating a new one.In either case, the string pointed to by<i>string</i>becomes part of theenvironment, so altering the string will change the environment.The space used by<i>string</i>is no longer used once a new string-defining<i>name</i>is passed to<i>putenv()</i>.<p>This interface need not be reentrant.</blockquote><h4><a name = "tag_000_007_1771"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,<i>putenv()</i>returns 0. Otherwise, it returns a non-zero value and sets<i>errno</i>to indicate the error.</blockquote><h4><a name = "tag_000_007_1772"> </a>ERRORS</h4><blockquote>The<i>putenv()</i>function may fail if:<dl compact><dt>[ENOMEM]<dd>Insufficient memory was available.</dl></blockquote><h4><a name = "tag_000_007_1773"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1774"> </a>APPLICATION USAGE</h4><blockquote>The<i>putenv()</i>function manipulates the environment pointed to by<i>environ</i>,and can be used in conjunction with<i><a href="getenv.html">getenv()</a></i>.<p>This routine may use<i><a href="malloc.html">malloc()</a></i>to enlarge the environment.<p>A potential error is to call<i>putenv()</i>with an automatic variable as the argument, then return from the callingfunction while<i>string</i>is still part of the environment.</blockquote><h4><a name = "tag_000_007_1775"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1776"> </a>SEE ALSO</h4><blockquote><i><a href="exec.html">exec</a></i>,<i><a href="getenv.html">getenv()</a></i>,<i><a href="malloc.html">malloc()</a></i>,<i><a href="stdlib.h.html"><stdlib.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from Issue 1 of the SVID.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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