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GETPRIORITY(2) | System Calls Manual | GETPRIORITY(2) |
NAME¶
getpriority
,
setpriority
—
get/set program scheduling priority
LIBRARY¶
Standard C Library (libc, -lc)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 thegetpriority
() system call and set with the
setpriority
() system call. The
which argument 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. The prio argument is a value
in the range -20 to 20. The default priority is 0; lower priorities cause more
favorable scheduling.
The getpriority
() system call returns the
highest priority (lowest numerical value) enjoyed by any of the specified
processes. The setpriority
() system call
sets the priorities of all of the specified processes to the specified value.
Only the super-user may lower priorities.
RETURN VALUES¶
Sincegetpriority
() 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.
ERRORS¶
Thegetpriority
() and
setpriority
() system calls will fail if:
- [
ESRCH
] - No process was located using the which and who values specified.
- [
EINVAL
] - The which argument was not one of
PRIO_PROCESS
,PRIO_PGRP
, orPRIO_USER
.
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¶
Thegetpriority
() system call appeared in
4.2BSD.June 4, 1993 | Debian |