1.\" $OpenBSD: getpriority.2,v 1.12 2007/05/31 19:19:32 jmc Exp $ 2.\" $NetBSD: getpriority.2,v 1.4 1995/02/27 12:33:15 cgd Exp $ 3.\" 4.\" Copyright (c) 1980, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: May 31 2007 $ 34.Dt GETPRIORITY 2 35.Os 36.Sh NAME 37.Nm getpriority , 38.Nm setpriority 39.Nd get/set program scheduling priority 40.Sh SYNOPSIS 41.Fd #include <sys/time.h> 42.Fd #include <sys/resource.h> 43.Ft int 44.Fn getpriority "int which" "id_t who" 45.Ft int 46.Fn setpriority "int which" "id_t who" "int prio" 47.Sh DESCRIPTION 48The scheduling priority of the process, process group, or user, 49as indicated by 50.Fa which 51and 52.Fa who 53is obtained with the 54.Fn getpriority 55call and set with the 56.Fn setpriority 57call. 58.Fa which 59is one of 60.Dv PRIO_PROCESS , 61.Dv PRIO_PGRP , 62or 63.Dv PRIO_USER , 64and 65.Fa who 66is interpreted relative to 67.Fa which 68(a process identifier for 69.Dv PRIO_PROCESS , 70process group identifier for 71.Dv PRIO_PGRP , 72and a user ID for 73.Dv PRIO_USER ) . 74A zero value of 75.Fa who 76denotes the current process, process group, or user. 77.Fa prio 78is a value in the range \-20 to 20. 79The default priority is 0; lower priorities cause more favorable scheduling. 80.Pp 81The 82.Fn getpriority 83call returns the highest priority (lowest numerical value) 84enjoyed by any of the specified processes. 85The 86.Fn setpriority 87call sets the priorities of all of the specified processes 88to the specified value. 89Priority values outside the range \-20 to 20 are truncated to the 90appropriate limit. 91Only the superuser may lower priorities. 92.Sh RETURN VALUES 93Since 94.Fn getpriority 95can legitimately return the value \-1, it is necessary 96to clear the external variable 97.Va errno 98prior to the 99call, then check it afterward to determine 100if a \-1 is an error or a legitimate value. 101The 102.Fn setpriority 103call returns 0 if there is no error, or 104\-1 if there is. 105.Sh ERRORS 106.Fn getpriority 107and 108.Fn setpriority 109will fail if: 110.Bl -tag -width Er 111.It Bq Er ESRCH 112No process was located using the 113.Fa which 114and 115.Fa who 116values specified. 117.It Bq Er EINVAL 118.Fa which 119was not one of 120.Dv PRIO_PROCESS , 121.Dv PRIO_PGRP , 122or 123.Dv PRIO_USER . 124.El 125.Pp 126In addition to the errors indicated above, 127.Fn setpriority 128will fail if: 129.Bl -tag -width Er 130.It Bq Er EPERM 131A process was located, but neither its effective nor real user 132ID matched the effective user ID of the caller. 133.It Bq Er EACCES 134A non-superuser attempted to lower a process priority. 135.El 136.Sh SEE ALSO 137.Xr nice 1 , 138.Xr fork 2 , 139.Xr renice 8 140.Sh HISTORY 141The 142.Fn getpriority 143function call appeared in 144.Bx 4.2 . 145