1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/getpriority.2,v 1.4.2.5 2001/12/14 18:34:00 ru Exp $ 30.\" $DragonFly: src/lib/libc/sys/getpriority.2,v 1.3 2008/05/01 23:36:43 swildner Exp $ 31.\" 32.Dd June 4, 1993 33.Dt GETPRIORITY 2 34.Os 35.Sh NAME 36.Nm getpriority , 37.Nm setpriority 38.Nd get/set program scheduling priority 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/time.h 43.In sys/resource.h 44.Ft int 45.Fn getpriority "int which" "int who" 46.Ft int 47.Fn setpriority "int which" "int who" "int prio" 48.Sh DESCRIPTION 49The scheduling 50priority of the process, process group, or user, as indicated by 51.Fa which 52and 53.Fa who 54is obtained with the 55.Fn getpriority 56call and set with the 57.Fn setpriority 58call. 59.Fa Which 60is one of 61.Dv PRIO_PROCESS , 62.Dv PRIO_PGRP , 63or 64.Dv PRIO_USER , 65and 66.Fa who 67is interpreted relative to 68.Fa which 69(a process identifier for 70.Dv PRIO_PROCESS , 71process group 72identifier for 73.Dv PRIO_PGRP , 74and a user ID for 75.Dv PRIO_USER ) . 76A zero value of 77.Fa who 78denotes the current process, process group, or user. 79.Fa Prio 80is a value in the range -20 to 20. The default priority is 0; 81lower priorities cause more favorable scheduling. 82.Pp 83The 84.Fn getpriority 85call returns the highest priority (lowest numerical value) 86enjoyed by any of the specified processes. The 87.Fn setpriority 88call sets the priorities of all of the specified processes 89to the specified value. Only the super-user may lower priorities. 90.Sh RETURN VALUES 91Since 92.Fn getpriority 93can legitimately return the value -1, it is necessary 94to clear the external variable 95.Va errno 96prior to the 97call, then check it afterward to determine 98if a -1 is an error or a legitimate value. 99.Pp 100.Rv -std setpriority 101.Sh ERRORS 102.Fn Getpriority 103and 104.Fn setpriority 105will fail if: 106.Bl -tag -width Er 107.It Bq Er ESRCH 108No process was located using the 109.Fa which 110and 111.Fa who 112values specified. 113.It Bq Er EINVAL 114.Fa Which 115was not one of 116.Dv PRIO_PROCESS , 117.Dv PRIO_PGRP , 118or 119.Dv PRIO_USER . 120.El 121.Pp 122In addition to the errors indicated above, 123.Fn setpriority 124will fail if: 125.Bl -tag -width Er 126.It Bq Er EPERM 127A process was located, but neither its effective nor real user 128ID matched the effective user ID of the caller. 129.It Bq Er EACCES 130A non super-user attempted to lower a process priority. 131.El 132.Sh SEE ALSO 133.Xr nice 1 , 134.Xr fork 2 , 135.Xr renice 8 136.Sh HISTORY 137The 138.Fn getpriority 139function call appeared in 140.Bx 4.2 . 141