View Source: getpriority(2) - Waikato Linux Users Group

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!!NAME
getpriority - get program scheduling priority
!!SYNOPSIS
 __#include <sys/time.h>__
 __#include <sys/resource.h>__

 __int getpriority(int__ ''which''__, int__ ''who''__);__

!!DESCRIPTION
The scheduling priority of the process, process group, or user, as indicated by ''which'' and ''who'' is obtained with the __getpriority__ call and set with the __setpriority__ call. ''Which'' is one of __PRIO_PROCESS__, __PRIO_PGRP__, or __PRIO_USER__,
and ''who'' is interpreted relative to ''which'' (a process identifier for __PRIO_PROCESS__, process group identifier for __PRIO_PGRP__, and a user ID for __PRIO_USER__). A zero value of ''who'' denotes the current process, process group, or user. ''Prio'' is a
value in the range -20 to 20. The default priority is 0; lower priorities cause more favorable scheduling.

The __getpriority__ call returns the highest priority (lowest numerical value) enjoyed by any of the specified processes. The __setpriority__ call sets the priorities of all of the specified processes to the specified value. Only the super-user may lower priorities.

!!RETURN VALUE
Since __getpriority__ can legitimately return the value -1, it is necessary to clear the external variable ''errno'' prior to the call, then check it afterwards to determine if a -1 is an error or a legitimate value. The __setpriority__ call returns 0 if there is no error, or -1 if there is.

!!ERRORS
;[ESRCH]: No process was located using the ''which'' and ''who'' values specified.
;[EINVAL]: ''Which'' was not one of __PRIO_PROCESS__, __PRIO_PGRP__, or __PRIO_USER__.

!!NOTE
The actual priority range varies between kernel versions.  Linux before 1.3.36 had -infinity..15. Linux since 1.3.43 has -20..19, and the  system  call  getpriority  returns  40..1 for these values (since negative numbers are error codes).  The library call converts N into 20-N.

Including ''<sys/time.h>'' is not required these days, but increases portability. (Indeed, ''<sys/resource.h>'' defines the ''rusage''
structure with fields of type ''struct timeval'' defined in ''<sys/time.h>''.)

!!CONFORMING TO
SVr4, 4.4BSD (these function calls first appeared in 4.2BSD).

!!SEE ALSO
nice(1), fork(2), renice(1)

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Last edited on Tuesday, December 31, 2002 1:45:33 am by PerryLorier

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