NICE(2)			   Linux Programmer's Manual		       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 low priority.)

       The range of the nice value is +19 (low priority) to -20	 (high	prior-
       ity).   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 unpriv-
       ileged 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  sup-
	      plying  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  cir-
       cumstances.  For details, see sched(7).

   C library/kernel differences
       POSIX.1	specifies  that nice() should return the new nice value.  How-
       ever, 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  pro-
       vides  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),  setprior-
       ity(2), capabilities(7), sched(7)

COLOPHON
       This  page  is  part of release 4.10 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/.



Linux				  2016-12-12			       NICE(2)