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<tr class="t-nv-h1"><td colspan="5"> Program termination</td></tr>
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<tr class="t-nv-h1"><td colspan="5"> Communicating with the environment</td></tr>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><strong class="selflink"><span class="t-lines"><span>getenv</span></span></strong></div></div></td></tr>
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<tr class="t-nv-h1"><td colspan="5"> Non-local jumps</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="setjmp.html" title="cpp/utility/program/setjmp"><span class="t-lines"><span>setjmp</span></span></a></div></div></td></tr>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="jmp_buf.html" title="cpp/utility/program/jmp buf"><span class="t-lines"><span>jmp_buf</span></span></a></div></div></td></tr>
</table></div><div><span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/utility/program/navbar_content&action=edit">[edit]</a></span></div></div></div></div><div class="t-navbar-sep"> </div></div>
<table class="t-dcl-begin"><tbody>
<tr class="t-dsc-header">
<td> <div>Defined in header <code><a href="../../header/cstdlib.html" title="cpp/header/cstdlib"><cstdlib></a></code>
</div></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span><span class="sy2">*</span> getenv<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> env_var <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td class="t-dcl-nopad"> </td>
<td class="t-dcl-nopad"> </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
</tbody></table>
<p>Searches the <i>environment list</i> provided by the host environment (the OS), for a string that matches the C string pointed to by <code>env_var</code> and returns a pointer to the C string that is associated with the matched environment list member.
</p>
<table class="t-rev-begin">
<tr class="t-rev t-until-cxx11"><td>
<p>This function is not required to be thread-safe. Another call to getenv, as well as a call to the POSIX functions <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/setenv.html">setenv()</a>, <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/unsetenv.html">unsetenv()</a>, and <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/putenv.html">putenv()</a> may invalidate the pointer returned by a previous call or modify the string obtained from a previous call.
</p>
</td>
<td><span class="t-mark-rev t-until-cxx11">(until C++11)</span></td></tr>
<tr class="t-rev t-since-cxx11"><td>
<p>This function is thread-safe (calling it from multiple threads does not introduce a data race) as long as no other function modifies the host environment. In particular, the POSIX functions <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/setenv.html">setenv()</a>, <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/unsetenv.html">unsetenv()</a>, and <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/putenv.html">putenv()</a> would introduce a data race if called without synchronization.
</p>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<p>Modifying the string returned by <code>getenv</code> invokes undefined behavior.
</p>
<table id="toc" class="toc"><tr><td><div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="getenv.html#Parameters"><span class="tocnumber">1</span> <span class="toctext">Parameters</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="getenv.html#Return_value"><span class="tocnumber">2</span> <span class="toctext">Return value</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="getenv.html#Notes"><span class="tocnumber">3</span> <span class="toctext">Notes</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="getenv.html#Example"><span class="tocnumber">4</span> <span class="toctext">Example</span></a></li>
<li class="toclevel-1 tocsection-5"><a href="getenv.html#See_also"><span class="tocnumber">5</span> <span class="toctext">See also</span></a></li>
</ul>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/utility/program/getenv&action=edit&section=1" title="Edit section: Parameters">edit</a>]</span> <span class="mw-headline" id="Parameters">Parameters</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td> env_var
</td>
<td> -
</td>
<td> null-terminated character string identifying the name of the environmental variable to look for
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/utility/program/getenv&action=edit&section=2" title="Edit section: Return value">edit</a>]</span> <span class="mw-headline" id="Return_value">Return value</span></h3>
<p>Character string identifying the value of the environmental variable or null pointer if such variable is not found.
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/utility/program/getenv&action=edit&section=3" title="Edit section: Notes">edit</a>]</span> <span class="mw-headline" id="Notes">Notes</span></h3>
<p>On POSIX systems, the <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08">environment variables</a> are also accessible through the global variable <code>environ</code>, declared as <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">extern</span> <span class="kw4">char</span> <span class="sy2">**</span>environ<span class="sy4">;</span></span></span> in <code><unistd.h></code>, and through the optional third argument, <code>envp</code>, of <a href="../../language/main_function.html" title="cpp/language/main function">the main function</a>.
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/utility/program/getenv&action=edit&section=4" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span></h3>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include <iostream></span>
<span class="co2">#include <cstdlib></span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">if</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> env_p <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">getenv</span><span class="br0">(</span><span class="st0">"PATH"</span><span class="br0">)</span><span class="br0">)</span>
<a href="../../io/cout.html"><span class="kw1480">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Your PATH is: "</span> <span class="sy1"><<</span> env_p <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Possible output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">Your PATH is: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games</pre></div></div>
</div>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/utility/program/getenv&action=edit&section=5" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td colspan="2"> <div class="t-dsc-see"><span><a href="../../../c/program/getenv.html" title="c/program/getenv">C documentation</a></span> for <span class="t-dsc-see-tt"><span>getenv</span></span></div>
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