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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>sem_close</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_008_270"> </a>NAME</h4><blockquote>sem_close - close a named semaphore(<b>REALTIME</b>)</blockquote><h4><a name = "tag_000_008_271"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="semaphore.h.html">semaphore.h</a>>int sem_close(sem_t *<i>sem</i>);</code></pre></blockquote><h4><a name = "tag_000_008_272"> </a>DESCRIPTION</h4><blockquote>The<i>sem_close()</i>function is used to indicate that the calling process is finishedusing the named semaphore indicated by<i>sem</i>.The effects of calling<i>sem_close()</i>for an unnamed semaphore (one created by<i><a href="sem_init.html">sem_init()</a></i>)are undefined.The<i>sem_close()</i>function deallocates(that is, make available for reuse by a subsequent<i><a href="sem_open.html">sem_open()</a></i>by this process)any system resources allocated by the systemfor 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<i><a href="sem_unlink.html">sem_unlink()</a></i>,then<i>sem_close()</i>has no effect on the state of the semaphore.If the<i><a href="sem_unlink.html">sem_unlink()</a></i>function has been successfully invoked for<i>name</i>after the most recent call to<i><a href="sem_open.html">sem_open()</a></i>with O_CREAT for this semaphore,then when all processes that have opened the semaphore close it,the semaphore is no longer be accessible.</blockquote><h4><a name = "tag_000_008_273"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,a value of zero is returned.Otherwise,a value of -1is returned and<i>errno</i>is set to indicatethe error.</blockquote><h4><a name = "tag_000_008_274"> </a>ERRORS</h4><blockquote>The <i>sem_close()</i>function will fail if:<dl compact><dt>[EINVAL]<dd>The<i>sem</i>argument is not a valid semaphore descriptor.<dt>[ENOSYS]<dd>The function<i>sem_close()</i>is not supported by this implementation.</dl></blockquote><h4><a name = "tag_000_008_275"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_008_276"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_008_277"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_008_278"> </a>SEE ALSO</h4><blockquote><i><a href="semctl.html">semctl()</a></i>,<i><a href="semget.html">semget()</a></i>,<i><a href="semop.html">semop()</a></i>,<i><a href="sem_init.html">sem_init()</a></i>,<i><a href="sem_open.html">sem_open()</a></i>,<i><a href="sem_unlink.html">sem_unlink()</a></i>,<i><a href="semaphore.h.html"><semaphore.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995)</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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