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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title><semaphore.h></title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="<semaphore.h>"></a> <a name="tag_13_41"></a><!-- <semaphore.h> --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_13_41_01"></a>NAME</h4><blockquote>semaphore.h - semaphores (<b>REALTIME</b>)</blockquote><h4><a name="tag_13_41_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><tt><sup>[<a href="javascript:open_code('SEM')">SEM</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <semaphore.h> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></div></blockquote><h4><a name="tag_13_41_03"></a>DESCRIPTION</h4><blockquote><p>The <i><semaphore.h></i> header shall define the <b>sem_t</b> type, used in performing semaphore operations. The semaphoremay be implemented using a file descriptor, in which case applications are able to open up at least a total of {OPEN_MAX} files andsemaphores. The symbol SEM_FAILED shall be defined (see <a href="../functions/sem_open.html"><i>sem_open</i>()</a>).</p><p>The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.</p><pre><tt>int sem_close(sem_t *);int sem_destroy(sem_t *);int sem_getvalue(sem_t *restrict, int *restrict);int sem_init(sem_t *, int, unsigned);sem_t *sem_open(const char *, int, ...);int sem_post(sem_t *);<sup>[<a href="javascript:open_code('TMO')">TMO</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">int sem_timedwait(sem_t *restrict, const struct timespec *restrict);<img src="../images/opt-end.gif" alt="[Option End]" border="0">int sem_trywait(sem_t *);int sem_unlink(const char *);int sem_wait(sem_t *);</tt></pre><p>Inclusion of the <i><semaphore.h></i> header may make visible symbols defined in the headers <a href="../basedefs/fcntl.h.html"><i><fcntl.h></i></a> and <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a>.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_13_41_04"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_41_05"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_41_06"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_41_07"></a>SEE ALSO</h4><blockquote><p><a href="fcntl.h.html"><i><fcntl.h></i></a> , <a href="sys/types.h.html"><i><sys/types.h></i></a> , the SystemInterfaces volume of IEEE Std 1003.1-2001, <a href="../functions/sem_destroy.html"><i>sem_destroy</i>()</a>, <a href="../functions/sem_getvalue.html"><i>sem_getvalue</i>()</a>, <a href="../functions/sem_init.html"><i>sem_init</i>()</a>, <a href="../functions/sem_open.html"><i>sem_open</i>()</a>, <a href="../functions/sem_post.html"><i>sem_post</i>()</a>, <a href="../functions/sem_timedwait.html"><i>sem_timedwait</i>()</a>, <a href="../functions/sem_trywait.html"><i>sem_trywait</i>()</a>, <ahref="../functions/sem_unlink.html"><i>sem_unlink</i>()</a>, <a href="../functions/sem_wait.html"><i>sem_wait</i>()</a></p></blockquote><h4><a name="tag_13_41_08"></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_13_41_09"></a>Issue 6</h4><blockquote><p>The <i><semaphore.h></i> header is marked as part of the Semaphores option.</p><p>The Open Group Corrigendum U021/3 is applied, adding a description of SEM_FAILED.</p><p>The <a href="../functions/sem_timedwait.html"><i>sem_timedwait</i>()</a> function is added for alignment withIEEE Std 1003.1d-1999.</p><p>The <b>restrict</b> keyword is added to the prototypes for <a href="../functions/sem_getvalue.html"><i>sem_getvalue</i>()</a>and <a href="../functions/sem_timedwait.html"><i>sem_timedwait</i>()</a>.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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