GETPRIORITY(2)GETPRIORITY(2)NAME
getpriority, setpriority - get/set program scheduling priority
SYNOPSIS
#include <sys/resource.h>
prio = getpriority(which, who)
int prio, which, who;
setpriority(which, who, prio)
int which, who, 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 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
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 may return one of the following 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.
In addition to the errors indicated above, setpriority may fail with
one of the following errors returned:
[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 ALSOnice(1), fork(2), renice(8)4th Berkeley Distribution May 22, 1986 GETPRIORITY(2)