129 lines
4.5 KiB
HTML
129 lines
4.5 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>unsetenv</title>
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<basefont size="3"> <a name="unsetenv"></a> <a name="tag_03_804"></a><!-- unsetenv -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_804_01"></a>NAME</h4>
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<blockquote>unsetenv - remove an environment variable</blockquote>
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<h4><a name="tag_03_804_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/stdlib.h.html">stdlib.h</a>><br>
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<br>
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int unsetenv(const char *</tt><i>name</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_804_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>unsetenv</i>() function shall remove an environment variable from the environment of the calling process. The <i>name</i>
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argument points to a string, which is the name of the variable to be removed. The named argument shall not contain an <tt>'='</tt>
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character. If the named variable does not exist in the current environment, the environment shall be unchanged and the function is
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considered to have completed successfully.</p>
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<p>If the application modifies <i>environ</i> or the pointers to which it points, the behavior of <i>unsetenv</i>() is undefined.
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The <i>unsetenv</i>() function shall update the list of pointers to which <i>environ</i> points.</p>
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<p>The <i>unsetenv</i>() function need not be reentrant. A function that is not required to be reentrant is not required to be
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thread-safe.</p>
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</blockquote>
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<h4><a name="tag_03_804_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, zero shall be returned. Otherwise, -1 shall be returned, <i>errno</i> set to indicate the error, and
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the environment shall be unchanged.</p>
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</blockquote>
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<h4><a name="tag_03_804_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>unsetenv</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The <i>name</i> argument is a null pointer, points to an empty string, or points to a string containing an <tt>'='</tt>
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character.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_804_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_804_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_804_08"></a>RATIONALE</h4>
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<blockquote>
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<p>Refer to the RATIONALE section in <a href="setenv.html"><i>setenv</i>()</a> .</p>
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</blockquote>
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<h4><a name="tag_03_804_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_804_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="getenv.html"><i>getenv</i>()</a> , <a href="setenv.html"><i>setenv</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/stdlib.h.html"><i><stdlib.h></i></a>, <a href=
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"../basedefs/sys/types.h.html"><i><sys/types.h></i></a>, <a href="../basedefs/unistd.h.html"><i><unistd.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_804_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from the IEEE P1003.1a draft standard.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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