1.\" $OpenBSD: nice.3,v 1.18 2013/07/18 10:14:48 schwarze 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: July 18 2013 $ 31.Dt NICE 3 32.Os 33.Sh NAME 34.Nm nice 35.Nd change process scheduling priority 36.Sh SYNOPSIS 37.In unistd.h 38.Ft int 39.Fn nice "int incr" 40.Sh DESCRIPTION 41.Bf -symbolic 42This interface is obsoleted by 43.Xr setpriority 2 . 44.Ef 45.Pp 46The 47.Fn nice 48function adds the value specified in 49.Fa incr 50to the scheduling priority of the invoking process. 51.Pp 52.Fa incr 53is an integer such that the resulting scheduling priority 54is within the range \-20 to 20. 55Priority values outside this range are truncated to the appropriate limit. 56The default priority is 0; lower priorities cause more favorable scheduling. 57Only the superuser may lower priorities. 58.Pp 59Children inherit the priority of their parent processes via 60.Xr fork 2 . 61.Sh RETURN VALUES 62On success, 63.Fn nice 64returns the new priority. 65On error, it returns -1. 66.Pp 67Since 68.Fn nice 69can legitimately return the value -1, it is necessary 70to clear the external variable 71.Va errno 72prior to the 73call, then check it afterward to determine 74if a -1 is an error or a legitimate value. 75.Sh ERRORS 76.Fn nice 77has the same failure conditions as 78.Xr setpriority 2 . 79.Sh SEE ALSO 80.Xr nice 1 , 81.Xr fork 2 , 82.Xr setpriority 2 , 83.Xr renice 8 84.Sh HISTORY 85A 86.Fn nice 87system call first appeared in 88.At v3 . 89It has accepted an 90.Fa incr 91argument since 92.At v4 . 93