159 lines
6.5 KiB
HTML
159 lines
6.5 KiB
HTML
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<title>nanosleep</title>
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<basefont size="3"> <a name="nanosleep"></a> <a name="tag_03_402"></a><!-- nanosleep -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_402_01"></a>NAME</h4>
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<blockquote>nanosleep - high resolution sleep (<b>REALTIME</b>)</blockquote>
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<h4><a name="tag_03_402_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('TMR')">TMR</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/time.h.html">time.h</a>><br>
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<br>
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int nanosleep(const struct timespec *</tt><i>rqtp</i><tt>, struct timespec *</tt><i>rmtp</i><tt>); <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_402_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>nanosleep</i>() function shall cause the current thread to be suspended from execution until either the time interval
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specified by the <i>rqtp</i> argument has elapsed or a signal is delivered to the calling thread, and its action is to invoke a
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signal-catching function or to terminate the process. The suspension time may be longer than requested because the argument value
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is rounded up to an integer multiple of the sleep resolution or because of the scheduling of other activity by the system. But,
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except for the case of being interrupted by a signal, the suspension time shall not be less than the time specified by <i>rqtp</i>,
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as measured by the system clock CLOCK_REALTIME.</p>
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<p>The use of the <i>nanosleep</i>() function has no effect on the action or blockage of any signal.</p>
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</blockquote>
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<h4><a name="tag_03_402_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>If the <i>nanosleep</i>() function returns because the requested time has elapsed, its return value shall be zero.</p>
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<p>If the <i>nanosleep</i>() function returns because it has been interrupted by a signal, it shall return a value of -1 and set
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<i>errno</i> to indicate the interruption. If the <i>rmtp</i> argument is non-NULL, the <b>timespec</b> structure referenced by it
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is updated to contain the amount of time remaining in the interval (the requested time minus the time actually slept). If the
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<i>rmtp</i> argument is NULL, the remaining time is not returned.</p>
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<p>If <i>nanosleep</i>() fails, it shall return a value of -1 and set <i>errno</i> to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_402_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>nanosleep</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EINTR]</dt>
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<dd>The <i>nanosleep</i>() function was interrupted by a signal.</dd>
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<dt>[EINVAL]</dt>
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<dd>The <i>rqtp</i> argument specified a nanosecond value less than zero or greater than or equal to 1000 million.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_402_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_402_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_402_08"></a>RATIONALE</h4>
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<blockquote>
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<p>It is common to suspend execution of a process for an interval in order to poll the status of a non-interrupting function. A
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large number of actual needs can be met with a simple extension to <a href="../functions/sleep.html"><i>sleep</i>()</a> that
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provides finer resolution.</p>
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<p>In the POSIX.1-1990 standard and SVR4, it is possible to implement such a routine, but the frequency of wakeup is limited by the
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resolution of the <a href="../functions/alarm.html"><i>alarm</i>()</a> and <a href="../functions/sleep.html"><i>sleep</i>()</a>
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functions. In 4.3 BSD, it is possible to write such a routine using no static storage and reserving no system facilities. Although
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it is possible to write a function with similar functionality to <a href="../functions/sleep.html"><i>sleep</i>()</a> using the
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remainder of the <a href="../functions/timer_create.html"><i>timer_*</i>()</a> functions, such a function requires the use of signals
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and the reservation of some signal number. This volume of IEEE Std 1003.1-2001 requires that <i>nanosleep</i>() be
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non-intrusive of the signals function.</p>
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<p>The <i>nanosleep</i>() function shall return a value of 0 on success and -1 on failure or if interrupted. This latter case is
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different from <a href="../functions/sleep.html"><i>sleep</i>()</a>. This was done because the remaining time is returned via an
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argument structure pointer, <i>rmtp</i>, instead of as the return value.</p>
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</blockquote>
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<h4><a name="tag_03_402_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_402_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="sleep.html"><i>sleep</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/time.h.html"><i><time.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_402_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p>
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</blockquote>
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<h4><a name="tag_03_402_12"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>nanosleep</i>() function is marked as part of the Timers option.</p>
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<p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Timers
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option.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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