Linux manual pages Section 2  

Name

nice — change process priority

Synopsis

#include <unistd.h>
int nice( int inc);
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
nice():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE

DESCRIPTION

nice() adds inc to the nice value for the calling process. (A higher nice value means a low priority.) Only the superuser may specify a negative increment, or priority increase. The range for nice values is described in getpriority(2).

RETURN VALUE

On success, the new nice value is returned (but see NOTES below). On error, −1 is returned, and errno is set appropriately.

ERRORS

EPERM

The calling process attempted to increase its priority by supplying a negative inc but has insufficient privileges. Under Linux the CAP_SYS_NICE capability is required. (But see the discussion of the RLIMIT_NICE resource limit in setrlimit(2).)

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001. However, the Linux and (g)libc (earlier than glibc 2.2.4) return value is nonstandard, see below. SVr4 documents an additional EINVAL error code.

NOTES

SUSv2 and POSIX.1-2001 specify that nice() should return the new nice value. However, the Linux syscall and the nice() library function provided in older versions of (g)libc (earlier than glibc 2.2.4) return 0 on success. The new nice value can be found using getpriority(2).

Since glibc 2.2.4, nice() is implemented as a library function that calls getpriority(2) to obtain the new nice value to be returned to the caller. With this implementation, a successful call can legitimately return −1. To reliably detect an error, set errno to 0 before the call, and check its value when nice() returns −1.

SEE ALSO

nice(1), renice(1), fork(2), getpriority(2), setpriority(2), capabilities(7)

COLOPHON

This page is part of release 3.33 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man-pages/.


Copyright (c) 1992 Drew Eckhardt <drewcs.colorado.edu>, March 28, 1992

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Modified by Michael Haardt <michaelmoria.de>
Modified 1993-07-24 by Rik Faith <faithcs.unc.edu>
Modified 1996-11-04 by Eric S. Raymond <esrthyrsus.com>
Modified 2001-06-04 by aeb
Modified 2004-05-27 by Michael Kerrisk <mtk.manpagesgmail.com>