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. 88The default priority is 0; 89lower priorities cause more favorable scheduling. 90.Pp 91The 92.Fn getpriority 93system call returns the highest priority (lowest numerical value) 94enjoyed by any of the specified processes. 95The 96.Fn setpriority 97system call sets the priorities of all of the specified processes 98to the specified value. 99Only the super-user may lower priorities. 100.Sh RETURN VALUES 101Since 102.Fn getpriority 103can legitimately return the value -1, it is necessary 104to clear the external variable 105.Va errno 106prior to the 107call, then check it afterward to determine 108if a -1 is an error or a legitimate value. 109.Pp 110.Rv -std setpriority 111.Sh ERRORS 112The 113.Fn getpriority 114and 115.Fn setpriority 116system calls 117will fail if: 118.Bl -tag -width Er 119.It Bq Er ESRCH 120No process was located using the 121.Fa which 122and 123.Fa who 124values specified. 125.It Bq Er EINVAL 126The 127.Fa which 128argument 129was not one of 130.Dv PRIO_PROCESS , 131.Dv PRIO_PGRP , 132or 133.Dv PRIO_USER . 134.El 135.Pp 136.Bl -tag -width Er 137In addition to the errors indicated above, 138.Fn setpriority 139will fail if: 140.It Bq Er EPERM 141A process was located, but neither its effective nor real user 142ID matched the effective user ID of the caller. 143.It Bq Er EACCES 144A non super-user attempted to lower a process priority. 145.El 146.Sh SEE ALSO 147.Xr nice 1 , 148.Xr fork 2 , 149.Xr renice 8 150.Sh HISTORY 151The 152.Fn getpriority 153system call appeared in 154.Bx 4.2 . 155