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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>usleep</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_010_298"> </a>NAME</h4><blockquote>usleep - suspend execution for an interval</blockquote><h4><a name = "tag_000_010_299"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="unistd.h.html">unistd.h</a>>int usleep(useconds_t <i>useconds</i>);</code></pre></blockquote><h4><a name = "tag_000_010_300"> </a>DESCRIPTION</h4><blockquote>The<i>usleep()</i>function will cause the calling thread to be suspended fromexecution until either the number of real-time microseconds specifiedby the argument<i>useconds</i>has elapsed or a signal is delivered to the calling thread and its action is to invoke a signal-catching function or toterminate the process.The suspension time may be longer than requested due to thescheduling of other activity by the system.<p>The <i>useconds</i> argument must be less than 1,000,000. If the value of<i>useconds</i> is 0, then the call has no effect.<p>If a SIGALRM signal is generated for the calling process duringexecution of<i>usleep()</i>and if the SIGALRM signal is being ignored or blockedfrom delivery, it is unspecified whether<i>usleep()</i>returns when the SIGALRM signal is scheduled.If the signal is being blocked, it is also unspecified whether itremains pending after<i>usleep()</i>returns or it is discarded.<p>If a SIGALRM signal is generated for the calling process duringexecution of<i>usleep()</i>,except as a result of a prior call to<i><a href="alarm.html">alarm()</a></i>,and if the SIGALRM signal is not being ignored orblocked from delivery, it is unspecified whether that signal hasany effect other than causing<i>usleep()</i>to return.<p>If a signal-catching function interrupts<i>usleep()</i>and examines or changes either the time a SIGALRM isscheduled to be generated, the action associated with the SIGALRMsignal, or whether the SIGALRM signal is blocked from delivery,the results are unspecified.<p>If a signal-catching function interrupts<i>usleep()</i>and calls<i><a href="siglongjmp.html">siglongjmp()</a></i>or<i><a href="longjmp.html">longjmp()</a></i>to restore an environment saved prior to the<i>usleep()</i>call, the action associated with the SIGALRM signal and the timeat which a SIGALRM signal is scheduled to be generated areunspecified.It is also unspecified whether the SIGALRM signal is blocked,unless the process' signal mask is restored as part of theenvironment.<p>Implementations may place limitations on the granularity of timer values.For each interval timer, if the requested timer value requires a finergranularity than the implementation supports, the actual timer value will berounded up to the next supported value.<p>Interactions between<i>usleep()</i>and any of the following are unspecified:<p><i><a href="nanosleep.html">nanosleep()</a></i><pre><i><a href="setitimer.html">setitimer()</a></i><i><a href="timer_create.html">timer_create()</a></i><i><a href="timer_delete.html">timer_delete()</a></i><i><a href="timer_getoverrun.html">timer_getoverrun()</a></i><i><a href="timer_gettime.html">timer_gettime()</a></i><i><a href="timer_settime.html">timer_settime()</a></i><i><a href="ualarm.html">ualarm()</a></i><i><a href="sleep.html">sleep()</a></i></pre></blockquote><h4><a name = "tag_000_010_301"> </a>RETURN VALUE</h4><blockquote>On successful completion,<i>usleep()</i>returns 0.Otherwise, it returns -1 and sets <i>errno</i> to indicate the error.</blockquote><h4><a name = "tag_000_010_302"> </a>ERRORS</h4><blockquote>The<i>usleep()</i>function may fail if:<dl compact><dt>[EINVAL]<dd>The time interval specified 1,000,000 or more microseconds.</dl></blockquote><h4><a name = "tag_000_010_303"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_010_304"> </a>APPLICATION USAGE</h4><blockquote>Applications are recommended to use<i><a href="setitimer.html">setitimer()</a></i>,<i><a href="timer_create.html">timer_create()</a></i>,<i><a href="timer_delete.html">timer_delete()</a></i>,<i><a href="timer_getoverrun.html">timer_getoverrun()</a></i>,<i><a href="timer_gettime.html">timer_gettime()</a></i>or<i><a href="timer_settime.html">timer_settime()</a></i>instead of this interface.</blockquote><h4><a name = "tag_000_010_305"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_010_306"> </a>SEE ALSO</h4><blockquote><i><a href="alarm.html">alarm()</a></i>,<i><a href="getitimer.html">getitimer()</a></i>,<i><a href="nanosleep.html">nanosleep()</a></i>,<i><a href="sigaction.html">sigaction()</a></i>,<i><a href="sleep.html">sleep()</a></i>,<i><a href="timer_create.html">timer_create()</a></i>,<i><a href="timer_delete.html">timer_delete()</a></i>,<i><a href="timer_getoverrun.html">timer_getoverrun()</a></i>,<i><a href="timer_gettime.html">timer_gettime()</a></i>,<i><a href="timer_settime.html">timer_settime()</a></i>,<i><a href="unistd.h.html"><unistd.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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