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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>nice</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="nice"></a> <a name="tag_03_406"></a><!-- nice --> <!--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_406_01"></a>NAME</h4><blockquote>nice - change the nice value of a process</blockquote><h4><a name="tag_03_406_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/unistd.h.html">unistd.h</a>><br><br> int nice(int</tt> <i>incr</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_406_03"></a>DESCRIPTION</h4><blockquote><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 isa non-negative number for which a more positive value shall result in less favorable scheduling.</p><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 orbelow these limits shall result in the nice value being set to the corresponding limit. Only a process with appropriate privilegescan lower the nice value.</p><p><sup>[<a href="javascript:open_code('PS')">PS|TPS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Calling the <i>nice</i>() function has no effect on the priority of processes or threads with policy SCHED_FIFO or SCHED_RR. Theeffect on processes or threads with other scheduling policies is implementation-defined. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p>The nice value set with <i>nice</i>() shall be applied to the process. If the process is multi-threaded, the nice value shallaffect all system scope threads in the process.</p><p>As -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set<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></blockquote><h4><a name="tag_03_406_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>nice</i>() shall return the new nice value -{NZERO}. Otherwise, -1 shall be returned, theprocess' nice value shall not be changed, and <i>errno</i> shall be set to indicate the error.</p></blockquote><h4><a name="tag_03_406_05"></a>ERRORS</h4><blockquote><p>The <i>nice</i>() function shall fail if:</p><dl compact><dt>[EPERM]</dt><dd>The <i>incr</i> argument is negative and the calling process does not have appropriate privileges.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_406_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_406_06_01"></a>Changing the Nice Value</h5><p>The following example adds the value of the <i>incr</i> argument, -20, to the nice value of the calling process.</p><pre><tt>#include <unistd.h>...int incr = -20;int ret;<br>ret = nice(incr);</tt></pre></blockquote><h4><a name="tag_03_406_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_406_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_406_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_406_10"></a>SEE ALSO</h4><blockquote><p><a href="getpriority.html"><i>getpriority</i>()</a> , <a href="setpriority.html"><i>setpriority</i>()</a> , the Base Definitionsvolume of IEEE Std 1003.1-2001, <a href="../basedefs/limits.h.html"><i><limits.h></i></a>, <a href="../basedefs/unistd.h.html"><i><unistd.h></i></a></p></blockquote><h4><a name="tag_03_406_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_406_12"></a>Issue 5</h4><blockquote><p>A statement is added to the description indicating the effects of this function on the different scheduling policies andmulti-threaded processes.</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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