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

       nice - change process priority

       #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

       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

       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.

       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).)

       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

       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.

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

       This page is part of release 5.07 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)