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.Dd June 4, 1993 29.Dt GETPRIORITY 2 30.Os 31.Sh NAME 32.Nm getpriority , 33.Nm setpriority 34.Nd get/set program scheduling priority 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In sys/time.h 39.In sys/resource.h 40.Ft int 41.Fn getpriority "int which" "int who" 42.Ft int 43.Fn setpriority "int which" "int who" "int prio" 44.Sh DESCRIPTION 45The scheduling 46priority of the process, process group, or user, as indicated by 47.Fa which 48and 49.Fa who 50is obtained with the 51.Fn getpriority 52system call and set with the 53.Fn setpriority 54system call. 55The 56.Fa which 57argument 58is one of 59.Dv PRIO_PROCESS , 60.Dv PRIO_PGRP , 61or 62.Dv PRIO_USER , 63and 64.Fa who 65is interpreted relative to 66.Fa which 67(a process identifier for 68.Dv PRIO_PROCESS , 69process group 70identifier 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. 77The 78.Fa prio 79argument 80is a value in the range -20 to 20. 81The default priority is 0; 82lower priorities cause more favorable scheduling. 83.Pp 84The 85.Fn getpriority 86system call returns the highest priority (lowest numerical value) 87enjoyed by any of the specified processes. 88The 89.Fn setpriority 90system call sets the priorities of all of the specified processes 91to the specified value. 92Only the super-user may lower priorities. 93.Sh RETURN VALUES 94Since 95.Fn getpriority 96can legitimately return the value -1, it is necessary 97to clear the external variable 98.Va errno 99prior to the 100call, then check it afterward to determine 101if a -1 is an error or a legitimate value. 102.Pp 103.Rv -std setpriority 104.Sh ERRORS 105The 106.Fn getpriority 107and 108.Fn setpriority 109system calls 110will fail if: 111.Bl -tag -width Er 112.It Bq Er ESRCH 113No process was located using the 114.Fa which 115and 116.Fa who 117values specified. 118.It Bq Er EINVAL 119The 120.Fa which 121argument 122was not one of 123.Dv PRIO_PROCESS , 124.Dv PRIO_PGRP , 125or 126.Dv PRIO_USER . 127.El 128.Pp 129In addition to the errors indicated above, 130.Fn setpriority 131will fail if: 132.Bl -tag -width Er 133.It Bq Er EPERM 134A process was located, but neither its effective nor real user 135ID matched the effective user ID of the caller. 136.It Bq Er EACCES 137A non super-user attempted to lower a process priority. 138.El 139.Sh SEE ALSO 140.Xr nice 1 , 141.Xr fork 2 , 142.Xr renice 8 143.Sh HISTORY 144The 145.Fn getpriority 146system call appeared in 147.Bx 4.2 . 148