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.\"     @(#)nice.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: head/lib/libc/gen/nice.3 282008 2015-04-26 10:56:06Z bapt $
.\"
.Dd February 28, 2015
.Dt NICE 3
.Os
.Sh NAME
.Nm nice
.Nd set program scheduling priority
.Sh LIBRARY
.Lb libc
.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
.Fa incr
to the scheduling priority of the process.
The priority is a value in the range -20 to 20.
The default priority is 0; lower priorities cause more favorable scheduling.
Only the super-user may lower priorities.
.Pp
Children inherit the priority of their parent processes via
.Xr fork 2 .
.Sh RETURN VALUES
Upon successful completion,
.Fn nice
returns 0, and
.Va errno
is unchanged.
Otherwise, \-1 is returned, the process' nice value is not changed, and
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn nice
function will fail if:
.Bl -tag -width Er
.It Bq Er EPERM
The
.Fa incr
argument is negative and the caller does not have appropriate privileges.
.El
.Sh SEE ALSO
.Xr nice 1 ,
.Xr fork 2 ,
.Xr setpriority 2 ,
.Xr renice 8
.Sh STANDARDS
The
.Fn nice
function conforms to
.St -p1003.1-2008
except for the return value.
This implementation returns 0 upon successful completion but
the standard requires returning the new nice value,
which could be \-1.
.Sh HISTORY
A
.Fn nice
syscall appeared in
.At v6 .