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OpenDarwin 7.2.1 - man page for setpriority (opendarwin section 2)

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GETPRIORITY(2)			     BSD System Calls Manual			   GETPRIORITY(2)

NAME
     getpriority, setpriority -- get/set program scheduling priority

SYNOPSIS
     #include <sys/time.h>
     #include <sys/resource.h>

     int
     getpriority(int which, int who);

     int
     setpriority(int which, int who, int prio);

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 speci-
     fied processes to the specified value.  Only the super-user may lower priorities.

RETURN VALUES
     Since getpriority() can legitimately return the value -1, it is necessary to clear the
     external variable errno prior to the call, then check it afterward 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
     Getpriority() and setpriority() will fail if:

     [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.

     In addition to the errors indicated above, setpriority() will fail if:

     [EPERM]		A process was located, but neither its effective nor real user ID matched
			the effective user ID of the caller.

     [EACCES]		A non super-user attempted to lower a process priority.

SEE ALSO
     nice(1), fork(2), renice(8)

HISTORY
     The getpriority() function call appeared in 4.2BSD.

4th Berkeley Distribution		   June 4, 1993 		4th Berkeley Distribution
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