181 lines
6.7 KiB
HTML
181 lines
6.7 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>getitimer</title>
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<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
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<basefont size="3"> <a name="getitimer"></a> <a name="tag_03_229"></a><!-- getitimer -->
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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_229_01"></a>NAME</h4>
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<blockquote>getitimer, setitimer - get and set value of interval timer</blockquote>
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<h4><a name="tag_03_229_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('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/sys/time.h.html">sys/time.h</a>><br>
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<br>
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int getitimer(int</tt> <i>which</i><tt>, struct itimerval *</tt><i>value</i><tt>);<br>
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int setitimer(int</tt> <i>which</i><tt>, const struct itimerval *restrict</tt> <i>value</i><tt>,<br>
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struct itimerval *restrict</tt> <i>ovalue</i><tt>); <img src="../images/opt-end.gif" alt=
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"[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_229_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>getitimer</i>() function shall store the current value of the timer specified by <i>which</i> into the structure pointed
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to by <i>value</i>. The <i>setitimer</i>() function shall set the timer specified by <i>which</i> to the value specified in the
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structure pointed to by <i>value</i>, and if <i>ovalue</i> is not a null pointer, store the previous value of the timer in the
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structure pointed to by <i>ovalue</i>.</p>
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<p>A timer value is defined by the <b>itimerval</b> structure, specified in <a href=
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"../basedefs/sys/time.h.html"><i><sys/time.h></i></a>. If <i>it_value</i> is non-zero, it shall indicate the time to the next
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timer expiration. If <i>it_interval</i> is non-zero, it shall specify a value to be used in reloading <i>it_value</i> when the
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timer expires. Setting <i>it_value</i> to 0 shall disable a timer, regardless of the value of <i>it_interval</i>. Setting
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<i>it_interval</i> to 0 shall disable a timer after its next expiration (assuming <i>it_value</i> is non-zero).</p>
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<p>Implementations may place limitations on the granularity of timer values. For each interval timer, if the requested timer value
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requires a finer granularity than the implementation supports, the actual timer value shall be rounded up to the next supported
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value.</p>
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<p>An XSI-conforming implementation provides each process with at least three interval timers, which are indicated by the
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<i>which</i> argument:</p>
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<dl compact>
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<dt>ITIMER_REAL</dt>
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<dd>Decrements in real time. A SIGALRM signal is delivered when this timer expires.</dd>
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<dt>ITIMER_VIRTUAL</dt>
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<dd>Decrements in process virtual time. It runs only when the process is executing. A SIGVTALRM signal is delivered when it
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expires.</dd>
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<dt>ITIMER_PROF</dt>
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<dd>Decrements both in process virtual time and when the system is running on behalf of the process. It is designed to be used by
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interpreters in statistically profiling the execution of interpreted programs. Each time the ITIMER_PROF timer expires, the SIGPROF
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signal is delivered.</dd>
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</dl>
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<p>The interaction between <i>setitimer</i>() and any of <a href="../functions/alarm.html"><i>alarm</i>()</a>, <a href=
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"../functions/sleep.html"><i>sleep</i>()</a>, or <a href="../functions/usleep.html"><i>usleep</i>()</a> is unspecified.</p>
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</blockquote>
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<h4><a name="tag_03_229_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>getitimer</i>() or <i>setitimer</i>() shall return 0; otherwise, -1 shall be returned and
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<i>errno</i> set to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_229_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>setitimer</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The <i>value</i> argument is not in canonical form. (In canonical form, the number of microseconds is a non-negative integer
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less than 1000000 and the number of seconds is a non-negative integer.)</dd>
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</dl>
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<p>The <i>getitimer</i>() and <i>setitimer</i>() functions may fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The <i>which</i> argument is not recognized.</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_229_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_229_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_229_08"></a>RATIONALE</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_229_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_229_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="alarm.html"><i>alarm</i>()</a> , <a href="sleep.html"><i>sleep</i>()</a> , <a href=
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"timer_getoverrun.html"><i>timer_getoverrun</i>()</a> , <a href="ualarm.html"><i>ualarm</i>()</a> , <a href=
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"usleep.html"><i>usleep</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/signal.h.html"><i><signal.h></i></a>, <a href="../basedefs/sys/time.h.html"><i><sys/time.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_229_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4, Version 2.</p>
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</blockquote>
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<h4><a name="tag_03_229_12"></a>Issue 5</h4>
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<blockquote>
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<p>Moved from X/OPEN UNIX extension to BASE.</p>
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</blockquote>
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<h4><a name="tag_03_229_13"></a>Issue 6</h4>
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<blockquote>
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<p>The <b>restrict</b> keyword is added to the <i>setitimer</i>() prototype for alignment with the ISO/IEC 9899:1999
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standard.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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