1.\" $NetBSD: getpriority.2,v 1.14 2003/04/16 13:34:52 wiz Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt GETPRIORITY 2 38.Os 39.Sh NAME 40.Nm getpriority , 41.Nm setpriority 42.Nd get/set program scheduling priority 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.In sys/resource.h 47.Ft int 48.Fn getpriority "int which" "int who" 49.Ft int 50.Fn setpriority "int which" "int who" "int prio" 51.Sh DESCRIPTION 52The scheduling 53priority of the process, process group, or user, as indicated by 54.Fa which 55and 56.Fa who 57is obtained with the 58.Fn getpriority 59call and set with the 60.Fn setpriority 61call. 62.Fa which 63is one of 64.Dv PRIO_PROCESS , 65.Dv PRIO_PGRP , 66or 67.Dv PRIO_USER , 68and 69.Fa who 70is interpreted relative to 71.Fa which 72(a process identifier for 73.Dv PRIO_PROCESS , 74process group 75identifier for 76.Dv PRIO_PGRP , 77and a user ID for 78.Dv PRIO_USER ) . 79A zero value of 80.Fa who 81denotes the current process, process group, or user. 82.Fa prio 83is a value in the range -20 to 20. 84The default priority is 0; 85lower priorities cause more favorable scheduling. 86A value of 19 or 20 87will schedule a process only when nothing at priority \*(Le 0 is runnable. 88.Pp 89The 90.Fn getpriority 91call returns the highest priority (lowest numerical value) 92enjoyed by any of the specified processes. 93The 94.Fn setpriority 95call sets the priorities of all of the specified processes 96to the specified value. 97Only the super-user may lower priorities. 98.Sh RETURN VALUES 99Since 100.Fn getpriority 101can legitimately return the value -1, it is necessary 102to clear the external variable 103.Va errno 104prior to the 105call, then check it afterward to determine 106if a -1 is an error or a legitimate value. 107The 108.Fn setpriority 109call returns 0 if there is no error, or 110-1 if there is. 111.Sh ERRORS 112.Fn getpriority 113and 114.Fn setpriority 115will fail if: 116.Bl -tag -width Er 117.It Bq Er ESRCH 118No process was located using the 119.Fa which 120and 121.Fa who 122values specified. 123.It Bq Er EINVAL 124.Fa which 125was not one of 126.Dv PRIO_PROCESS , 127.Dv PRIO_PGRP , 128or 129.Dv PRIO_USER . 130.El 131.Pp 132.Bl -tag -width Er 133In addition to the errors indicated above, 134.Fn setpriority 135will fail if: 136.It Bq Er EPERM 137A process was located, but neither its effective nor real user 138ID matched the effective user ID of the caller. 139.It Bq Er EACCES 140A non super-user attempted to lower a process priority. 141.El 142.Sh SEE ALSO 143.Xr nice 1 , 144.Xr fork 2 , 145.Xr renice 8 146.Sh HISTORY 147The 148.Fn getpriority 149function call appeared in 150.Bx 4.2 . 151