Copyright (c) 1980 Regents of the University of California. All rights reserved. The Berkeley software License Agreement specifies the terms and conditions for redistribution. @(#)getpriority.2 6.6 (Berkeley) 02/06/89 GETPRIORITY 2 ""
C 4 NAME
getpriority, setpriority -
get/
set program scheduling priority
SYNOPSIS
#include <sys/time.h>
#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:
15
[ESRCH]
No process was located using the
which and
who values specified.
15
[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:
15
[EPERM]
A process was located, but neither its effective nor real user
ID matched the effective user ID of the caller.
15
[EACCES]
A non super-user attempted to lower a process priority.
"SEE ALSO"
nice(1), fork(2), renice(8)