1<html lang="en"> 2<head> 3<title>getenv - 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="exit.html#exit" title="exit"> 10<link rel="next" href="labs.html#labs" title="labs"> 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="getenv"></a> 29<p> 30Next: <a rel="next" accesskey="n" href="labs.html#labs">labs</a>, 31Previous: <a rel="previous" accesskey="p" href="exit.html#exit">exit</a>, 32Up: <a rel="up" accesskey="u" href="Stdlib.html#Stdlib">Stdlib</a> 33<hr> 34</div> 35 36<h3 class="section">2.18 <code>getenv</code>—look up environment variable</h3> 37 38<p><a name="index-getenv-31"></a><a name="index-environ-32"></a><strong>Synopsis</strong> 39<pre class="example"> #include <stdlib.h> 40 char *getenv(const char *<var>name</var>); 41 42</pre> 43 <p><strong>Description</strong><br> 44<code>getenv</code> searches the list of environment variable names and values 45(using the global pointer “<code>char **environ</code>”) for a variable whose 46name matches the string at <var>name</var>. If a variable name matches, 47<code>getenv</code> returns a pointer to the associated value. 48 49 <p><br> 50<strong>Returns</strong><br> 51A pointer to the (string) value of the environment variable, or 52<code>NULL</code> if there is no such environment variable. 53 54 <p><br> 55<strong>Portability</strong><br> 56<code>getenv</code> is ANSI, but the rules for properly forming names of environment 57variables vary from one system to another. 58 59 <p><code>getenv</code> requires a global pointer <code>environ</code>. 60 61 <p><br> 62 63 </body></html> 64 65