nice(2) — Linux manual page


NICE(2)                   Linux Programmer's Manual                  NICE(2)

NAME         top

       nice - change process priority

SYNOPSIS         top

       #include <unistd.h>

       int nice(int inc);

   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         top

       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

RETURN VALUE         top

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

       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         top

       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

CONFORMING TO         top

       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         top

       For further details on the nice value, see sched(7).

       Note: 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         top

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

COLOPHON         top

       This page is part of release 5.09 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

Linux                            2017-09-15                          NICE(2)

Pages that refer to this page: nice(1)getpriority(2)getrlimit(2)prlimit(2)prlimit64(2)sched_getaffinity(2)sched_getattr(2)sched_getparam(2)sched_getscheduler(2)sched_setaffinity(2)sched_setattr(2)sched_setparam(2)sched_setscheduler(2)setpriority(2)setrlimit(2)syscalls(2)ugetrlimit(2)vlimit(3)capabilities(7)sched(7)