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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd June 4, 1993 36.Dt GETPRIORITY 2 37.Os 38.Sh NAME 39.Nm getpriority , 40.Nm setpriority 41.Nd get/set program scheduling priority 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/time.h 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 59system call and set with the 60.Fn setpriority 61system call. 62The 63.Fa which 64argument 65is one of 66.Dv PRIO_PROCESS , 67.Dv PRIO_PGRP , 68or 69.Dv PRIO_USER , 70and 71.Fa who 72is interpreted relative to 73.Fa which 74(a process identifier for 75.Dv PRIO_PROCESS , 76process group 77identifier for 78.Dv PRIO_PGRP , 79and a user ID for 80.Dv PRIO_USER ) . 81A zero value of 82.Fa who 83denotes the current process, process group, or user. 84The 85.Fa prio 86argument 87is a value in the range -20 to 20. The default priority is 0; 88lower priorities cause more favorable scheduling. 89.Pp 90The 91.Fn getpriority 92system call returns the highest priority (lowest numerical value) 93enjoyed by any of the specified processes. The 94.Fn setpriority 95system call sets the priorities of all of the specified processes 96to the specified value. Only the super-user may lower priorities. 97.Sh RETURN VALUES 98Since 99.Fn getpriority 100can legitimately return the value -1, it is necessary 101to clear the external variable 102.Va errno 103prior to the 104call, then check it afterward to determine 105if a -1 is an error or a legitimate value. 106.Pp 107.Rv -std setpriority 108.Sh ERRORS 109The 110.Fn getpriority 111and 112.Fn setpriority 113system calls 114will fail if: 115.Bl -tag -width Er 116.It Bq Er ESRCH 117No process was located using the 118.Fa which 119and 120.Fa who 121values specified. 122.It Bq Er EINVAL 123The 124.Fa which 125argument 126was not one of 127.Dv PRIO_PROCESS , 128.Dv PRIO_PGRP , 129or 130.Dv PRIO_USER . 131.El 132.Pp 133.Bl -tag -width Er 134In addition to the errors indicated above, 135.Fn setpriority 136will fail if: 137.It Bq Er EPERM 138A process was located, but neither its effective nor real user 139ID matched the effective user ID of the caller. 140.It Bq Er EACCES 141A non super-user attempted to lower a process priority. 142.El 143.Sh SEE ALSO 144.Xr nice 1 , 145.Xr fork 2 , 146.Xr renice 8 147.Sh HISTORY 148The 149.Fn getpriority 150system call appeared in 151.Bx 4.2 . 152