opensolaris man page for nice

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 5.11							    1 Apr 2004								   nice(2)