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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><sys/sem.h></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_009_336"> </a>NAME</h4><blockquote>sys/sem.h - semaphore facility</blockquote><h4><a name = "tag_000_009_337"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <sys/sem.h></code></pre></blockquote><h4><a name = "tag_000_009_338"> </a>DESCRIPTION</h4><blockquote>The <<b>sys/sem.h</b>> header defines the following constants andstructures.<p>Semaphore operation flags:<dl compact><dt>SEM_UNDO<dd>Set up adjust on exit entry.</dl><p>Command definitions for the function<i><a href="semctl.html">semctl()</a></i>:<dl compact><dt>GETNCNT<dd>Get<b>semncnt</b>.<dt>GETPID<dd>Get<b>sempid</b>.<dt>GETVAL<dd>Get<b>semval</b>.<dt>GETALL<dd>Get all cases of<b>semval</b>.<dt>GETZCNT<dd>Get<b>semzcnt</b>.<dt>SETVAL<dd>Set<b>semval</b>.<dt>SETALL<dd>Set all cases of<b>semval</b>.</dl><p>The structure<b>semid_ds</b>contains the following members:<pre><code>struct ipc_perm sem_perm operation permission structureunsigned short int sem_nsems number of semaphores in settime_t sem_otime last <i>semop</i>^) timetime_t sem_ctime last time changed by <i>semctl</i>()</code></pre><p>The<b>pid_t</b>,<b>time_t</b>,<b>key_t</b>and<b>size_t</b>types are defined as described in<i><a href="systypes.h.html"><sys/types.h></a></i>.<p>A semaphore is represented by an anonymousstructure containing the following members:<pre><code>unsigned short int semval semaphore valuepid_t sempid process ID of last operationunsigned short int semncnt number of processes waiting for <b>semval</b> to become greater than current valueunsigned short int semzcnt number of processes waiting for <b>semval</b> to become 0</code></pre><p>The structure<b>sembuf</b>contains the following members:<pre><code>unsigned short int sem_num semaphore numbershort int sem_op semaphore operationshort int sem_flg operation flags</code></pre><p>The following are declared as functions and may also be definedas macros.Function prototypes must be provided for use with an ISO Ccompiler.<pre><code>int <a href="semctl.html">semctl</a>(int, int, int, ...);int <a href="semget.html">semget</a>(key_t, int, int);int <a href="semop.html">semop</a>(int, struct sembuf *, size_t);</code></pre><p>In addition, all of the symbols from<i><a href="sysipc.h.html"><sys/ipc.h></a></i>will be defined when this header is included.</blockquote><h4><a name = "tag_000_009_339"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_009_340"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_009_341"> </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="systypes.h.html"><sys/types.h></a></i>.</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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