Name
nice — change process priority
Synopsis
#include <unistd.h>
int
nice( |
int inc); |
![[Note]](../stylesheet/note.png) |
Note | ||||
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DESCRIPTION
nice() adds inc to the nice value for the
calling thread. (A higher nice value means a lower
priority.)
The range of the nice value is +19 (low priority) to −20 (high priority). Attempts to set a nice value outside the range are clamped to the range.
Traditionally, only a privileged process could lower the
nice value (i.e., set a higher priority). However, since
Linux 2.6.12, an unprivileged process can decrease the nice
value of a target process that has a suitable RLIMIT_NICE soft limit; see getrlimit(2) for
details.
RETURN VALUE
On success, the new nice value is returned (but see NOTES
below). On error, −1 is returned, and errno is set to indicate the error.
A successful call can legitimately return −1. To
detect an error, set errno to 0
before the call, and check whether it is nonzero after
nice() returns −1.
ERRORS
- EPERM
-
The calling process attempted to increase its priority by supplying a negative
incbut has insufficient privileges. Under Linux, theCAP_SYS_NICEcapability is required. (But see the discussion of theRLIMIT_NICEresource limit in setrlimit(2).)
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. However, the raw system call and (g)libc (earlier than glibc 2.2.4) return value is nonstandard, see below.
NOTES
For further details on the nice value, see sched(7).
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Note |
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the addition of the "autogroup" feature in Linux 2.6.38 means that the nice value no longer has its traditional effect in many circumstances. For details, see sched(7). |
C library/kernel differences
POSIX.1 specifies that nice() should return the new nice value.
However, the raw Linux system call returns 0 on success.
Likewise, the nice() wrapper
function provided in glibc 2.2.3 and earlier returns 0 on
success.
Since glibc 2.2.4, the nice() wrapper function provided by glibc
provides conformance to POSIX.1 by calling getpriority(2) to obtain
the new nice value, which is then returned to the
caller.
SEE ALSO
nice(1), renice(1), fork(2), getpriority(2), getrlimit(2), setpriority(2), capabilities(7), sched(7)
COLOPHON
This page is part of release 5.11 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/.
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Copyright (c) 1992 Drew Eckhardt <drewcs.colorado.edu>, March 28, 1992 %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END 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> |