1.\" $OpenBSD: getpriority.2,v 1.7 2000/10/18 05:12:09 aaron 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. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93 36.\" 37.Dd June 4, 1993 38.Dt GETPRIORITY 2 39.Os 40.Sh NAME 41.Nm getpriority , 42.Nm setpriority 43.Nd get/set program scheduling priority 44.Sh SYNOPSIS 45.Fd #include <sys/time.h> 46.Fd #include <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 priority of the process, process group, or user, 53as indicated by 54.Fa which 55and 56.Fa who 57is obtained with the 58.Fn getpriority 59call and set with the 60.Fn setpriority 61call. 62.Fa which 63is one of 64.Dv PRIO_PROCESS , 65.Dv PRIO_PGRP , 66or 67.Dv PRIO_USER , 68and 69.Fa who 70is interpreted relative to 71.Fa which 72(a process identifier for 73.Dv PRIO_PROCESS , 74process group identifier for 75.Dv PRIO_PGRP , 76and a user ID for 77.Dv PRIO_USER ) . 78A zero value of 79.Fa who 80denotes the current process, process group, or user. 81.Fa prio 82is a value in the range \-20 to 20. 83The default priority is 0; 84lower priorities cause more favorable scheduling. 85.Pp 86The 87.Fn getpriority 88call returns the highest priority (lowest numerical value) 89enjoyed by any of the specified processes. 90The 91.Fn setpriority 92call sets the priorities of all of the specified processes 93to the specified value. 94Only the superuser may lower priorities. 95.Sh RETURN VALUES 96Since 97.Fn getpriority 98can legitimately return the value \-1, it is necessary 99to clear the external variable 100.Va errno 101prior to the 102call, then check it afterward to determine 103if a \-1 is an error or a legitimate value. 104The 105.Fn setpriority 106call returns 0 if there is no error, or 107\-1 if there is. 108.Sh ERRORS 109.Fn getpriority 110and 111.Fn setpriority 112will fail if: 113.Bl -tag -width Er 114.It Bq Er ESRCH 115No process was located using the 116.Fa which 117and 118.Fa who 119values specified. 120.It Bq Er EINVAL 121.Fa which 122was not one of 123.Dv PRIO_PROCESS , 124.Dv PRIO_PGRP , 125or 126.Dv PRIO_USER . 127.El 128.Pp 129.Bl -tag -width Er 130In addition to the errors indicated above, 131.Fn setpriority 132will fail if: 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-superuser 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 146function call appeared in 147.Bx 4.2 . 148