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.\" $FreeBSD$ 30.\" 31.Dd June 4, 1993 32.Dt GETPRIORITY 2 33.Os 34.Sh NAME 35.Nm getpriority , 36.Nm setpriority 37.Nd get/set program scheduling priority 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/time.h 42.In sys/resource.h 43.Ft int 44.Fn getpriority "int which" "int who" 45.Ft int 46.Fn setpriority "int which" "int who" "int prio" 47.Sh DESCRIPTION 48The scheduling 49priority of the process, process group, or user, as indicated by 50.Fa which 51and 52.Fa who 53is obtained with the 54.Fn getpriority 55system call and set with the 56.Fn setpriority 57system call. 58The 59.Fa which 60argument 61is one of 62.Dv PRIO_PROCESS , 63.Dv PRIO_PGRP , 64or 65.Dv PRIO_USER , 66and 67.Fa who 68is interpreted relative to 69.Fa which 70(a process identifier for 71.Dv PRIO_PROCESS , 72process group 73identifier for 74.Dv PRIO_PGRP , 75and a user ID for 76.Dv PRIO_USER ) . 77A zero value of 78.Fa who 79denotes the current process, process group, or user. 80The 81.Fa prio 82argument 83is a value in the range -20 to 20. 84The default priority is 0; 85lower priorities cause more favorable scheduling. 86.Pp 87The 88.Fn getpriority 89system call returns the highest priority (lowest numerical value) 90enjoyed by any of the specified processes. 91The 92.Fn setpriority 93system call sets the priorities of all of the specified processes 94to the specified value. 95Only the super-user may lower priorities. 96.Sh RETURN VALUES 97Since 98.Fn getpriority 99can legitimately return the value -1, it is necessary 100to clear the external variable 101.Va errno 102prior to the 103call, then check it afterward to determine 104if a -1 is an error or a legitimate value. 105.Pp 106.Rv -std setpriority 107.Sh ERRORS 108The 109.Fn getpriority 110and 111.Fn setpriority 112system calls 113will fail if: 114.Bl -tag -width Er 115.It Bq Er ESRCH 116No process was located using the 117.Fa which 118and 119.Fa who 120values specified. 121.It Bq Er EINVAL 122The 123.Fa which 124argument 125was not one of 126.Dv PRIO_PROCESS , 127.Dv PRIO_PGRP , 128or 129.Dv PRIO_USER . 130.El 131.Pp 132In addition to the errors indicated above, 133.Fn setpriority 134will fail if: 135.Bl -tag -width Er 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 149system call appeared in 150.Bx 4.2 . 151