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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>getpriority</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_005_683"> </a>NAME</h4><blockquote>getpriority, setpriority - get or set the nice value</blockquote><h4><a name = "tag_000_005_684"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="sysresource.h.html">sys/resource.h</a>>int getpriority(int <i>which</i>, id_t <i>who</i>);int setpriority(int <i>which</i>, id_t <i>who</i>, int <i>value</i>);</code></pre></blockquote><h4><a name = "tag_000_005_685"> </a>DESCRIPTION</h4><blockquote>The<i>getpriority()</i>function obtains the nice value of a process, process group or user.The<i>setpriority()</i>function sets the nice value of a process, process group or user to<i>value</i>+ NZERO.<p>Target processes are specified by the values of the <i>which</i> and <i>who</i>arguments. The <i>which</i> argument may be one of the following values:PRIO_PROCESS, PRIO_PGRP or PRIO_USER, indicating that the <i>who</i> argumentis to be interpreted as a process ID, a process group ID or aneffective user ID, respectively. A 0 value for the <i>who</i> argument specifies the current process,process group or user.<p>The nice value set with<i>setpriority()</i>is applied to the process.If the process is multi-threaded, the nice value affects allsystem scope threads in the process.<p>If more than one process is specified,<i>getpriority()</i>returns value NZERO less than the lowest nice value pertainingto any of the specified processes, and<i>setpriority()</i>sets the nice values of all of the specified processes to<i>value</i>+ NZERO.<p>The default nice value is NZERO; lower nice values cause morefavourable scheduling.While the range of valid nice values is [0, NZERO*2 -1],implementations may enforce more restrictive limits.If<i>value</i>+ NZERO is less than the system's lowest supported nice value,<i>setpriority()</i>sets the nice value to the lowest supported value; if<i>value</i>+ NZERO is greater than the system's highest supported nice value,<i>setpriority()</i>sets the nice value to the highest supported value.<p>Only a process with appropriate privileges can lower its nice value.<p>Any processes or threads using SCHED_FIFO or SCHED_RR are unaffectedby a call to<i>setpriority()</i>.This is not considered an error.<p>The effect of changing the nice value may vary depending on theprocess-scheduling algorithm in effect.<p>Because<i>getpriority()</i>can return the value -1 on successful completion, it is necessary to set<i>errno</i> to 0 prior to a call to<i>getpriority()</i>.If<i>getpriority()</i>returns the value -1, then <i>errno</i> can be checked to see if anerror occurred or if the value is a legitimate nice value.</blockquote><h4><a name = "tag_000_005_686"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,<i>getpriority()</i>returns an integer in the range from -NZERO to NZERO-1.Otherwise, -1 is returned and <i>errno</i> is set to indicatethe error.<p>Upon successful completion,<i>setpriority()</i>returns 0.Otherwise, -1 is returned and <i>errno</i> is set to indicate the error.</blockquote><h4><a name = "tag_000_005_687"> </a>ERRORS</h4><blockquote>The<i>getpriority()</i>and<i>setpriority()</i>functions will fail if:<dl compact><dt>[ESRCH]<dd>No process could be located using the <i>which</i>and <i>who</i> argument values specified.<dt>[EINVAL]<dd>The value of the <i>which</i> argument was not recognised,or the value of the <i>who</i> argument is not a validprocess ID, process group ID or user ID.</dl><p>In addition,<i>setpriority()</i>may fail if:<dl compact><dt>[EPERM]<dd>A process was located, but neither the real nor effective user ID ofthe executing process match the effective user ID of the process whosenice value is being changed.<dt>[EACCES]<dd>A request was made to change the nice valueto a lower numeric value and the current process does not haveappropriate privileges.</dl></blockquote><h4><a name = "tag_000_005_688"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_005_689"> </a>APPLICATION USAGE</h4><blockquote>The<i>getpriority()</i>and<i>setpriority()</i>functions work with an offset nice value (nice value minus NZERO).The nice value is in the range [0, 2*NZERO -1], while the returnvalue for<i>getpriority()</i>and the third parameter for<i>setpriority()</i>are in the range [-NZERO, NZERO -1].</blockquote><h4><a name = "tag_000_005_690"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_005_691"> </a>SEE ALSO</h4><blockquote><i><a href="nice.html">nice()</a></i>,<i><a href="sched_get_priority_max.html">sched_get_priority_max()</a></i>,<i><a href="sched_setscheduler.html">sched_setscheduler()</a></i>,<i><a href="sysresource.h.html"><sys/resource.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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