nice(2) - Linux manual page (original) (raw)

nice(2) System Calls Manual nice(2)

NAME top

   nice - change process priority

LIBRARY top

   Standard C library (_libc_, _-lc_)

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)](../man2/getrlimit.2.html) for details.

RETURN VALUE top

   On success, the new nice value is returned (but see VERSIONS
   below).  On error, -1 is returned, and _[errno](../man3/errno.3.html)_ is set to indicate
   the error.

   A successful call can legitimately return -1.  To detect an error,
   set _[errno](../man3/errno.3.html)_ 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)](../man2/setrlimit.2.html).)

VERSIONS top

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)](../man2/getpriority.2.html) to
   obtain the new nice value, which is then returned to the caller.

STANDARDS top

   POSIX.1-2008.

HISTORY top

   POSIX.1-2001, SVr4, 4.3BSD.

NOTES top

   For further details on the nice value, see [sched(7)](../man7/sched.7.html).

   _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)](../man7/sched.7.html).

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Linux man-pages 6.10 2024-07-23 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)