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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 superuser privileges 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  effective  user  ID of the calling process is not
           superuser.

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



SunOS 5.9            Last change: 6 Mar 2002                    1






System Calls                                              nice(2)



     Since -1 is a  permissible  return  value  in  a  successful
     situation,  an application wishing to check for error situa-
     tions 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  attri-
     butes:

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


SEE ALSO
     nice(1),  exec(2),  priocntl(2),   getpriority(3C),   attri-
     butes(5), standards(5)


































SunOS 5.9            Last change: 6 Mar 2002                    2