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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  <&lt;limits.h>&gt;  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 effec-
                tive set of the calling process.



USAGE
       The priocntl(2) function is a more general interface to scheduler func-
       tions.

       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:


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).   ATTRIBUTE TYPEATTRIBUTE VALUE Interface StabilityStan-
       dard MT-LevelAsync-Signal-Safe


SEE ALSO
       nice(1), exec(2), priocntl(2), getpriority(3C),  attributes(5),  privi-
       leges(5), standards(5)



SunOS 5.10                        1 Apr 2004                           nice(2)