nice(2) [centos man page]

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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE

DESCRIPTION

       nice()  adds  inc to the nice value for the calling process.  (A higher nice value means a low priority.)  Only the superuser may specify a
       negative increment, or priority increase.  The range for nice values is described in getpriority(2).

RETURN VALUE

       On success, the new nice value is returned (but see NOTES below).  On error, -1 is returned, and errno is set appropriately.

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

       SVr4,  4.3BSD, POSIX.1-2001.  However, the Linux and (g)libc (earlier than glibc 2.2.4) return value is nonstandard, see below.	SVr4 docu-
       ments an additional EINVAL error code.

NOTES

       SUSv2 and POSIX.1-2001 specify that nice() should return the new nice value.  However, the Linux syscall and the  nice()  library  function
       provided  in  older  versions  of  (g)libc (earlier than glibc 2.2.4) return 0 on success.  The new nice value can be found using getprior-
       ity(2).

       Since glibc 2.2.4, nice() is implemented as a library function that calls getpriority(2) to obtain the new nice value to be returned to the
       caller.	 With  this  implementation, a successful call can legitimately return -1.  To reliably detect an error, set errno to 0 before the
       call, and check its value when nice() returns -1.

SEE ALSO

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

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2007-07-26								   NICE(2)

nice(2) 							   System Calls 							   nice(2)

NAME

       nice - change priority of a process

SYNOPSIS

       #include <unistd.h>

       int nice(int incr);

DESCRIPTION

       The nice() function allows a process to change its priority.  The invoking  process must be in a scheduling class that supports the nice().

       The  nice()  function adds the value of	incr to the nice value of the calling process. A process's nice value is a non-negative number for
       which a greater positive value results in lower CPU priority.

       A maximum nice value of (2 * NZERO) -1 and a minimum nice value of 0 are imposed by the system. NZERO  is  defined  in  <limits.h>  with  a
       default	value of 20. Requests for values above or below these limits result in the nice value being set to the corresponding limit. A nice
       value of 40 is treated as 39.

       Calling the nice() function has no effect on the priority of processes or threads with policy SCHED_FIFO or SCHED_RR.

       Only a process with the {PRIV_PROC_PRIOCNTL} privilege can lower the nice value.

RETURN VALUES

       Upon successful completion, nice() returns the new nice value minus NZERO. Otherwise, -1 is returned,  the  process's  nice  value  is  not
       changed, and errno is set to indicate the error.

ERRORS

       The nice() function will fail if:

       EINVAL	The nice() function is called by a process in a scheduling class other than time-sharing or fixed-priority.

       EPERM	The  incr  argument  is negative or greater than 40 and the {PRIV_PROC_PRIOCNTL} privilege is not asserted in the effective set of
		the calling process.

USAGE

       The priocntl(2) function is a more general interface to scheduler functions.

       Since -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set errno	to
       0, then call nice(), and if it returns -1, check to see if errno is non-zero.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       nice(1), exec(2), priocntl(2), getpriority(3C), attributes(5), privileges(5), standards(5)

SunOS 5.10							    1 Apr 2004								   nice(2)