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 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

       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

       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

       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

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

COLOPHON

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