NICE(2)                   (2017-09-15)                    NICE(2)

     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(): _XOPEN_SOURCE
              || /* Since glibc 2.19: */ _DEFAULT_SOURCE
              || /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
          _SVID_SOURCE

     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 appro-
          priately.

          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 inc but has insufficient privi-
               leges.  Under Linux, the CAP_SYS_NICE capability is
               required.  (But see the discussion of the RLIMIT_NICE
               resource 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

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     NICE(2)                   (2017-09-15)                    NICE(2)

          value is nonstandard, see below.

     NOTES
          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 tradi-
          tional 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 suc-
          cess.  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 5.10 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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