1.\" Copyright (c) 1980, 1991 The Regents of the University of California. 2.\" 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 6.9 (Berkeley) 3/10/91 33.\" 34.Dd March 10, 1991 35.Dt GETPRIORITY 2 36.Os BSD 4 37.Sh NAME 38.Nm getpriority , 39.Nm setpriority 40.Nd get/set program scheduling priority 41.Sh SYNOPSIS 42.Fd #include <sys/time.h> 43.Fd #include <sys/resource.h> 44.Ft int 45.Fn getpriority "int which" "int who" 46.Ft int 47.Fn setpriority "int which" "int who" "int prio" 48.Sh DESCRIPTION 49The scheduling 50priority of the process, process group, or user, as indicated by 51.Fa which 52and 53.Fa who 54is obtained with the 55.Fn getpriority 56call and set with the 57.Fn setpriority 58call. 59.Fa Which 60is one of 61.Dv PRIO_PROCESS , 62.Dv PRIO_PGRP , 63or 64.Dv PRIO_USER , 65and 66.Fa who 67is interpreted relative to 68.Fa which 69(a process identifier for 70.Dv PRIO_PROCESS , 71process group 72identifier for 73.Dv PRIO_PGRP , 74and a user ID for 75.Dv PRIO_USER ) . 76A zero value of 77.Fa who 78denotes the current process, process group, or user. 79.Fa Prio 80is a value in the range -20 to 20. The default priority is 0; 81lower priorities cause more favorable scheduling. 82.Pp 83The 84.Fn getpriority 85call returns the highest priority (lowest numerical value) 86enjoyed by any of the specified processes. The 87.Fn setpriority 88call sets the priorities of all of the specified processes 89to the specified value. Only the super-user may lower priorities. 90.Sh RETURN VALUES 91Since 92.Fn getpriority 93can legitimately return the value -1, it is necessary 94to clear the external variable 95.Va errno 96prior to the 97call, then check it afterward to determine 98if a -1 is an error or a legitimate value. 99The 100.Fn setpriority 101call returns 0 if there is no error, or 102-1 if there is. 103.Sh ERRORS 104.Fn Getpriority 105and 106.Fn setpriority 107will fail if: 108.Bl -tag -width Er 109.It Bq Er ESRCH 110No process was located using the 111.Fa which 112and 113.Fa who 114values specified. 115.It Bq Er EINVAL 116.Fa Which 117was not one of 118.Dv PRIO_PROCESS , 119.Dv PRIO_PGRP , 120or 121.Dv PRIO_USER . 122.El 123.Pp 124.Bl -tag -width Er 125In addition to the errors indicated above, 126.Fn setpriority 127will fail if: 128.It Bq Er EPERM 129A process was located, but neither its effective nor real user 130ID matched the effective user ID of the caller. 131.It Bq Er EACCES 132A non super-user attempted to lower a process priority. 133.El 134.Sh SEE ALSO 135.Xr nice 1 , 136.Xr fork 2 , 137.Xr renice 8 138.Sh HISTORY 139The 140.Nm 141function call appeared in 142.Bx 4.2 . 143