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GETPRIORITY(2) System Calls Manual GETPRIORITY(2)

getpriority, setpriority — get/set program scheduling priority

library “libc”

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

int
getpriority(int which, int who);

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

The scheduling priority of the process, process group, or user, as indicated by which and who is obtained with the () call and set with the () 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 () call returns the highest priority (lowest numerical value) enjoyed by any of the specified processes. The () call sets the priorities of all of the specified processes to the specified value. Only the super-user may lower priorities.

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() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

Getpriority() and setpriority() will fail if:

[]
No process was located using the which and who values specified.
[]
Which was not one of PRIO_PROCESS, PRIO_PGRP, or PRIO_USER.

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

[]
A process was located, but neither its effective nor real user ID matched the effective user ID of the caller.
[]
A non super-user attempted to lower a process priority.

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

The getpriority() function call appeared in 4.2BSD.

June 4, 1993 DragonFly-5.6.1