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.\" Copyright (c) 1992 Drew Eckhardt <drew@cs.colorado.edu>, March 28, 1992
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.\" Modified by Michael Haardt <michael@moria.de>
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1996-11-04 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 2001-06-04 by aeb
.\" Modified 2004-05-27 by Michael Kerrisk <mtk-manpages@gmx.net>
.\"
.TH NICE 2 2004-05-27 "Linux 2.6.6" "Linux Programmer's Manual"
.SH NAME
nice \- change process priority
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "int nice(int " inc );
.SH DESCRIPTION
.B nice
adds 
.I inc
to the nice value for the calling pid.
(A large nice value means a low priority.)
Only the super\%user may specify a negative increment, or priority increase.
.SH "RETURN VALUE"
On success, zero is returned.  On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EPERM
The calling process attempted to increase its priority by
supplying a negative
.IR inc
but has insufficient privileges.
Under Linux the
.B CAP_SYS_NICE
capability is required.
.SH "CONFORMING TO"
SVr4, SVID EXT, AT&T, X/OPEN, BSD 4.3. However, the Linux and glibc
(earlier than glibc 2.2.4) return value is nonstandard, see below.
SVr4 documents an additional
EINVAL error code.
.SH NOTES
Note that the routine is documented in SUSv2 and POSIX 1003.1-2003
to return the new nice value, while the Linux syscall and (g)libc
(earlier than glibc 2.2.4) routines return 0 on success.
The new nice value can be found using
.BR getpriority (2).
Note that an implementation in which
.B nice
returns the new nice value can legitimately return \-1.
To reliably detect an error, set
.I errno
to 0 before the call, and check its value when
.B nice
returns \-1.
.SH "SEE ALSO"
.BR nice (1),
.BR fork (2),
.BR getpriority (2),
.BR setpriority (2),
.BR capabilities (7),
.BR renice (8)