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nice.2

NICE

Section: Linux Programmer's Manual (2)
Updated: 2007-07-26
Index Return to Main Contents
 

NAME

nice - change process priority  

SYNOPSIS

#include <unistd.h>

int nice(int inc);

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 non-standard, 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), fork(2), getpriority(2), setpriority(2), capabilities(7), renice(8)  

COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

 

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