1.\" $NetBSD: getpriority.2,v 1.4 1995/02/27 12:33:15 cgd Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt GETPRIORITY 2 38.Os BSD 4 39.Sh NAME 40.Nm getpriority , 41.Nm setpriority 42.Nd get/set program scheduling priority 43.Sh SYNOPSIS 44.Fd #include <sys/time.h> 45.Fd #include <sys/resource.h> 46.Ft int 47.Fn getpriority "int which" "int who" 48.Ft int 49.Fn setpriority "int which" "int who" "int prio" 50.Sh DESCRIPTION 51The scheduling 52priority of the process, process group, or user, as indicated by 53.Fa which 54and 55.Fa who 56is obtained with the 57.Fn getpriority 58call and set with the 59.Fn setpriority 60call. 61.Fa Which 62is one of 63.Dv PRIO_PROCESS , 64.Dv PRIO_PGRP , 65or 66.Dv PRIO_USER , 67and 68.Fa who 69is interpreted relative to 70.Fa which 71(a process identifier for 72.Dv PRIO_PROCESS , 73process group 74identifier 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. The default priority is 0; 83lower priorities cause more favorable scheduling. 84.Pp 85The 86.Fn getpriority 87call returns the highest priority (lowest numerical value) 88enjoyed by any of the specified processes. The 89.Fn setpriority 90call sets the priorities of all of the specified processes 91to the specified value. Only the super-user may lower priorities. 92.Sh RETURN VALUES 93Since 94.Fn getpriority 95can legitimately return the value -1, it is necessary 96to clear the external variable 97.Va errno 98prior to the 99call, then check it afterward to determine 100if a -1 is an error or a legitimate value. 101The 102.Fn setpriority 103call returns 0 if there is no error, or 104-1 if there is. 105.Sh ERRORS 106.Fn Getpriority 107and 108.Fn setpriority 109will fail if: 110.Bl -tag -width Er 111.It Bq Er ESRCH 112No process was located using the 113.Fa which 114and 115.Fa who 116values specified. 117.It Bq Er EINVAL 118.Fa Which 119was not one of 120.Dv PRIO_PROCESS , 121.Dv PRIO_PGRP , 122or 123.Dv PRIO_USER . 124.El 125.Pp 126.Bl -tag -width Er 127In addition to the errors indicated above, 128.Fn setpriority 129will fail if: 130.It Bq Er EPERM 131A process was located, but neither its effective nor real user 132ID matched the effective user ID of the caller. 133.It Bq Er EACCES 134A non super-user attempted to lower a process priority. 135.El 136.Sh SEE ALSO 137.Xr nice 1 , 138.Xr fork 2 , 139.Xr renice 8 140.Sh HISTORY 141The 142.Fn getpriority 143function call appeared in 144.Bx 4.2 . 145