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.\" $OpenBSD: nice.3,v 1.18 2013/07/18 10:14:48 schwarze Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" notice, this list of conditions and the following disclaimer.
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.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\"
.Dd $Mdocdate: July 18 2013 $
.Dt NICE 3
.Os
.Sh NAME
.Nm nice
.Nd change process scheduling priority
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn nice "int incr"
.Sh DESCRIPTION
.Bf -symbolic
This interface is obsoleted by
.Xr setpriority 2 .
.Ef
.Pp
The
.Fn nice
function adds the value specified in
.Fa incr
to the scheduling priority of the invoking process.
.Pp
.Fa incr
is an integer such that the resulting scheduling priority
is within the range \-20 to 20.
Priority values outside this range are truncated to the appropriate limit.
The default priority is 0; lower priorities cause more favorable scheduling.
Only the superuser may lower priorities.
.Pp
Children inherit the priority of their parent processes via
.Xr fork 2 .
.Sh RETURN VALUES
On success,
.Fn nice
returns the new priority.
On error, it returns -1.
.Pp
Since
.Fn nice
can legitimately return the value -1, it is necessary
to clear the external variable
.Va errno
prior to the
call, then check it afterward to determine
if a -1 is an error or a legitimate value.
.Sh ERRORS
.Fn nice
has the same failure conditions as
.Xr setpriority 2 .
.Sh SEE ALSO
.Xr nice 1 ,
.Xr fork 2 ,
.Xr setpriority 2 ,
.Xr renice 8
.Sh HISTORY
A
.Fn nice
system call first appeared in
.At v3 .
It has accepted an
.Fa incr
argument since
.At v4 .
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