nice(2) — Linux manual page

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

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 <= 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 details.

RETURN VALUE         top

       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         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 setrlimit(2).)

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 5.11 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/.

Linux                          2021-03-22                        NICE(2)

Pages that refer to this page: nice(1)getpriority(2)getrlimit(2)sched_setaffinity(2)sched_setattr(2)sched_setparam(2)sched_setscheduler(2)syscalls(2)capabilities(7)sched(7)