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<center><font size="2">The Open Group Base Specifications Issue 6<br>
IEEE Std 1003.1-2001<br>
Copyright &copy; 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
<!--header end-->
<hr size="2" noshade>
<h4><a name="tag_03_628_01"></a>NAME</h4>
<blockquote>sem_close - close a named semaphore (<b>REALTIME</b>)</blockquote>
<h4><a name="tag_03_628_02"></a>SYNOPSIS</h4>
<blockquote class="synopsis">
<div class="box"><code><tt><sup>[<a href="javascript:open_code('SEM')">SEM</a>]</sup> <img src="../images/opt-start.gif" alt=
"[Option Start]" border="0"> #include &lt;<a href="../basedefs/semaphore.h.html">semaphore.h</a>&gt;<br>
<br>
int sem_close(sem_t *</tt><i>sem</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
<tt><br>
</tt></blockquote>
<h4><a name="tag_03_628_03"></a>DESCRIPTION</h4>
<blockquote>
<p>The <i>sem_close</i>() function shall indicate that the calling process is finished using the named semaphore indicated by
<i>sem</i>. The effects of calling <i>sem_close</i>() for an unnamed semaphore (one created by <a href=
"../functions/sem_init.html"><i>sem_init</i>()</a>) are undefined. The <i>sem_close</i>() function shall deallocate (that is, make
available for reuse by a subsequent <a href="../functions/sem_open.html"><i>sem_open</i>()</a> by this process) any system
resources allocated by the system for use by this process for this semaphore. The effect of subsequent use of the semaphore
indicated by <i>sem</i> by this process is undefined. If the semaphore has not been removed with a successful call to <a href=
"../functions/sem_unlink.html"><i>sem_unlink</i>()</a>, then <i>sem_close</i>() has no effect on the state of the semaphore. If the
<a href="../functions/sem_unlink.html"><i>sem_unlink</i>()</a> function has been successfully invoked for <i>name</i> after the
most recent call to <a href="../functions/sem_open.html"><i>sem_open</i>()</a> with O_CREAT for this semaphore, then when all
processes that have opened the semaphore close it, the semaphore is no longer accessible.</p>
</blockquote>
<h4><a name="tag_03_628_04"></a>RETURN VALUE</h4>
<blockquote>
<p>Upon successful completion, a value of zero shall be returned. Otherwise, a value of -1 shall be returned and <i>errno</i> set
to indicate the error.</p>
</blockquote>
<h4><a name="tag_03_628_05"></a>ERRORS</h4>
<blockquote>
<p>The <i>sem_close</i>() function shall fail if:</p>
<dl compact>
<dt>[EINVAL]</dt>
<dd>The <i>sem</i> argument is not a valid semaphore descriptor.</dd>
</dl>
</blockquote>
<hr>
<div class="box"><em>The following sections are informative.</em></div>
<h4><a name="tag_03_628_06"></a>EXAMPLES</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_03_628_07"></a>APPLICATION USAGE</h4>
<blockquote>
<p>The <i>sem_close</i>() function is part of the Semaphores option and need not be available on all implementations.</p>
</blockquote>
<h4><a name="tag_03_628_08"></a>RATIONALE</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_03_628_09"></a>FUTURE DIRECTIONS</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_03_628_10"></a>SEE ALSO</h4>
<blockquote>
<p><a href="semctl.html"><i>semctl</i>()</a> , <a href="semget.html"><i>semget</i>()</a> , <a href="semop.html"><i>semop</i>()</a>
, <a href="sem_init.html"><i>sem_init</i>()</a> , <a href="sem_open.html"><i>sem_open</i>()</a> , <a href=
"sem_unlink.html"><i>sem_unlink</i>()</a> , the Base Definitions volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../basedefs/semaphore.h.html"><i>&lt;semaphore.h&gt;</i></a></p>
</blockquote>
<h4><a name="tag_03_628_11"></a>CHANGE HISTORY</h4>
<blockquote>
<p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p>
</blockquote>
<h4><a name="tag_03_628_12"></a>Issue 6</h4>
<blockquote>
<p>The <i>sem_close</i>() function is marked as part of the Semaphores option.</p>
<p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Semaphores
option.</p>
</blockquote>
<div class="box"><em>End of informative text.</em></div>
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