154 lines
5.3 KiB
HTML
154 lines
5.3 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>nice</title>
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<basefont size="3"> <a name="nice"></a> <a name="tag_03_406"></a><!-- nice -->
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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_406_01"></a>NAME</h4>
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<blockquote>nice - change the nice value of a process</blockquote>
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<h4><a name="tag_03_406_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/unistd.h.html">unistd.h</a>><br>
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<br>
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int nice(int</tt> <i>incr</i><tt>); <img src="../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_406_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>nice</i>() function shall add the value of <i>incr</i> to the nice value of the calling process. A process' nice value is
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a non-negative number for which a more positive value shall result in less favorable scheduling.</p>
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<p>A maximum nice value of 2*{NZERO}-1 and a minimum nice value of 0 shall be imposed by the system. Requests for values above or
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below these limits shall result in the nice value being set to the corresponding limit. Only a process with appropriate privileges
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can lower the nice value.</p>
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<p><sup>[<a href="javascript:open_code('PS')">PS|TPS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Calling the <i>nice</i>() function has no effect on the priority of processes or threads with policy SCHED_FIFO or SCHED_RR. The
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effect on processes or threads with other scheduling policies is implementation-defined. <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></p>
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<p>The nice value set with <i>nice</i>() shall be applied to the process. If the process is multi-threaded, the nice value shall
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affect all system scope threads in the process.</p>
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<p>As -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set
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<i>errno</i> to 0, then call <i>nice</i>(), and if it returns -1, check to see whether <i>errno</i> is non-zero.</p>
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</blockquote>
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<h4><a name="tag_03_406_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>nice</i>() shall return the new nice value -{NZERO}. Otherwise, -1 shall be returned, the
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process' nice value shall not be changed, and <i>errno</i> shall be set to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_406_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>nice</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EPERM]</dt>
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<dd>The <i>incr</i> argument is negative and the calling process does not have appropriate privileges.</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_406_06"></a>EXAMPLES</h4>
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<blockquote>
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<h5><a name="tag_03_406_06_01"></a>Changing the Nice Value</h5>
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<p>The following example adds the value of the <i>incr</i> argument, -20, to the nice value of the calling process.</p>
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<pre>
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<tt>#include <unistd.h>
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...
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int incr = -20;
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int ret;
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<br>
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ret = nice(incr);
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_406_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_406_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_406_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_406_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="getpriority.html"><i>getpriority</i>()</a> , <a href="setpriority.html"><i>setpriority</i>()</a> , the Base Definitions
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volume of IEEE Std 1003.1-2001, <a href="../basedefs/limits.h.html"><i><limits.h></i></a>, <a href=
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"../basedefs/unistd.h.html"><i><unistd.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_406_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
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</blockquote>
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<h4><a name="tag_03_406_12"></a>Issue 5</h4>
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<blockquote>
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<p>A statement is added to the description indicating the effects of this function on the different scheduling policies and
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multi-threaded processes.</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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