GETPRIORITY (2)
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 specified 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 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 .
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.
CONFORMING TO
SVr4, 4.4BSD (these function calls first appeared in 4.2BSD).
SEE ALSO
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