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():
_XOPEN_SOURCE || /* Since glibc 2.19:
*/ _DEFAULT_SOURCE || /* Glibc versions <= 2.19:
*/ _BSD_SOURCE || _SVID_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

POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. 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 specify that nice() should return the new nice value. However, the Linux system call 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), sched(7)

COLOPHON

This page is part of release 4.07 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/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>