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OpenSolaris 2009.06 - man page for nice (opensolaris section 2)

nice(2) 				   System Calls 				  nice(2)

       nice - change priority of a process

       #include <unistd.h>

       int nice(int incr);

       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.

       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

       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.

       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.

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

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

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

SunOS 5.11				    1 Apr 2004					  nice(2)

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