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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>sem_timedwait</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="sem_timedwait"></a> <a name="tag_03_634"></a><!-- sem_timedwait --> <!--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_03_634_01"></a>NAME</h4><blockquote>sem_timedwait - lock a semaphore (<b>ADVANCED REALTIME</b>)</blockquote><h4><a name="tag_03_634_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('SEM TMO')">SEM TMO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/semaphore.h.html">semaphore.h</a>><br> #include <<a href="../basedefs/time.h.html">time.h</a>><br><br> int sem_timedwait(sem_t *restrict</tt> <i>sem</i><tt>,<br> const struct timespec *restrict</tt> <i>abs_timeout</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_634_03"></a>DESCRIPTION</h4><blockquote><p>The <i>sem_timedwait</i>() function shall lock the semaphore referenced by <i>sem</i> as in the <a href="../functions/sem_wait.html"><i>sem_wait</i>()</a> function. However, if the semaphore cannot be locked without waiting for anotherprocess or thread to unlock the semaphore by performing a <a href="../functions/sem_post.html"><i>sem_post</i>()</a> function, thiswait shall be terminated when the specified timeout expires.</p><p>The timeout shall expire when the absolute time specified by <i>abs_timeout</i> passes, as measured by the clock on whichtimeouts are based (that is, when the value of that clock equals or exceeds <i>abs_timeout</i>), or if the absolute time specifiedby <i>abs_timeout</i> has already been passed at the time of the call.</p><p><sup>[<a href="javascript:open_code('TMR')">TMR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">If the Timers option is supported, the timeout shall be based on the CLOCK_REALTIME clock. If the Timers option is not supported,the timeout shall be based on the system clock as returned by the <a href="../functions/time.html"><i>time</i>()</a> function. Theresolution of the timeout shall be the resolution of the clock on which it is based. The <b>timespec</b> data type is defined as astructure in the <a href="../basedefs/time.h.html"><i><time.h></i></a> header.</p><p>Under no circumstance shall the function fail with a timeout if the semaphore can be locked immediately. The validity of the<i>abs_timeout</i> need not be checked if the semaphore can be locked immediately. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_634_04"></a>RETURN VALUE</h4><blockquote><p>The <i>sem_timedwait</i>() function shall return zero if the calling process successfully performed the semaphore lock operationon the semaphore designated by <i>sem</i>. If the call was unsuccessful, the state of the semaphore shall be unchanged, and thefunction shall return a value of -1 and set <i>errno</i> to indicate the error.</p></blockquote><h4><a name="tag_03_634_05"></a>ERRORS</h4><blockquote><p>The <i>sem_timedwait</i>() function shall fail if:</p><dl compact><dt>[EINVAL]</dt><dd>The <i>sem</i> argument does not refer to a valid semaphore.</dd><dt>[EINVAL]</dt><dd>The process or thread would have blocked, and the <i>abs_timeout</i> parameter specified a nanoseconds field value less thanzero or greater than or equal to 1000 million.</dd><dt>[ETIMEDOUT]</dt><dd>The semaphore could not be locked before the specified timeout expired.</dd></dl><p>The <i>sem_timedwait</i>() function may fail if:</p><dl compact><dt>[EDEADLK]</dt><dd>A deadlock condition was detected.</dd><dt>[EINTR]</dt><dd>A signal interrupted this function.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_634_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_634_07"></a>APPLICATION USAGE</h4><blockquote><p>Applications using these functions may be subject to priority inversion, as discussed in the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap03.html#tag_03_285">Section 3.285, Priority Inversion</a>.</p><p>The <i>sem_timedwait</i>() function is part of the Semaphores and Timeouts options and need not be provided on allimplementations.</p></blockquote><h4><a name="tag_03_634_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_634_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_634_10"></a>SEE ALSO</h4><blockquote><p><a href="sem_post.html"><i>sem_post</i>()</a> , <a href="sem_trywait.html"><i>sem_trywait</i>()</a> , <a href="sem_wait.html"><i>sem_wait</i>()</a> , <a href="semctl.html"><i>semctl</i>()</a> , <a href="semget.html"><i>semget</i>()</a> , <ahref="semop.html"><i>semop</i>()</a> , <a href="time.html"><i>time</i>()</a> , the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/semaphore.h.html"><i><semaphore.h></i></a>, <a href="../basedefs/time.h.html"><i><time.h></i></a></p></blockquote><h4><a name="tag_03_634_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from IEEE Std 1003.1d-1999.</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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