[unix-history] / usr / src / lib / libc / sys / getpriority.2

.\" Copyright (c) 1980, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)getpriority.2	6.9 (Berkeley) %G%
.\"
.Dd 
.Dt GETPRIORITY 2
.Os BSD 4
.Sh NAME
.Nm getpriority ,
.Nm setpriority
.Nd get/set program scheduling priority
.Sh SYNOPSIS
.Fd #include <sys/time.h>
.Fd #include <sys/resource.h>
.Ft int
.Fn getpriority "int which" "int who"
.Ft int
.Fn setpriority "int which" "int who" "int prio"
.Sh DESCRIPTION
The scheduling
priority of the process, process group, or user, as indicated by
.Fa which
and
.Fa who
is obtained with the
.Fn getpriority
call and set with the
.Fn setpriority
call.
.Fa Which
is one of
.Dv PRIO_PROCESS ,
.Dv PRIO_PGRP ,
or
.Dv PRIO_USER ,
and 
.Fa who
is interpreted relative to 
.Fa which
(a process identifier for
.Dv PRIO_PROCESS ,
process group
identifier for
.Dv PRIO_PGRP ,
and a user ID for
.Dv PRIO_USER ) .
A zero value of
.Fa who
denotes the current process, process group, or user.
.Fa Prio
is a value in the range -20 to 20.  The default priority is 0;
lower priorities cause more favorable scheduling.
.Pp
The
.Fn getpriority
call returns the highest priority (lowest numerical value)
enjoyed by any of the specified processes.  The
.Fn setpriority
call sets the priorities of all of the specified processes
to the specified value.  Only the super-user may lower priorities.
.Sh RETURN VALUES
Since
.Fn getpriority
can legitimately return the value -1, it is necessary
to clear the external variable
.Va errno
prior to the
call, then check it afterward to determine
if a -1 is an error or a legitimate value.
The
.Fn setpriority
call returns 0 if there is no error, or
-1 if there is.
.Sh ERRORS
.Fn Getpriority
and
.Fn setpriority
will fail if:
.Bl -tag -width Er
.It Bq Er ESRCH
No process was located using the 
.Fa which
and
.Fa who
values specified.
.It Bq Er EINVAL
.Fa Which
was not one of
.Dv PRIO_PROCESS ,
.Dv PRIO_PGRP ,
or
.Dv PRIO_USER .
.El
.Pp
.Bl -tag -width Er
In addition to the errors indicated above,
.Fn setpriority
will fail if:
.It Bq Er EPERM
A process was located, but neither its effective nor real user
ID matched the effective user ID of the caller.
.It Bq Er EACCES
A non super-user attempted to lower a process priority.
.El
.Sh SEE ALSO
.Xr nice 1 ,
.Xr fork 2 ,
.Xr renice 8
.Sh HISTORY
The
.Nm
function call appeared in
.Bx 4.2 .
Commit	Line	Data
931b8415	1	.\" Copyright (c) 1980, 1991 The Regents of the University of California.
88b3ccf2	2	.\" All rights reserved.
e08c6f11	3	.\"
91cff1e1	4	.\" %sccs.include.redist.man%
88b3ccf2	5	.\"
931b8415	6	.\" @(#)getpriority.2 6.9 (Berkeley) %G%
e08c6f11	7	.\"
931b8415 CL	8	.Dd
	9	.Dt GETPRIORITY 2
	10	.Os BSD 4
	11	.Sh NAME
	12	.Nm getpriority ,
	13	.Nm setpriority
	14	.Nd get/set program scheduling priority
	15	.Sh SYNOPSIS
	16	.Fd #include <sys/time.h>
	17	.Fd #include <sys/resource.h>
	18	.Ft int
	19	.Fn getpriority "int which" "int who"
	20	.Ft int
	21	.Fn setpriority "int which" "int who" "int prio"
	22	.Sh DESCRIPTION
e08c6f11	23	The scheduling
e0304aa6	24	priority of the process, process group, or user, as indicated by
931b8415	25	.Fa which
e0304aa6	26	and
931b8415	27	.Fa who
e0304aa6	28	is obtained with the
931b8415	29	.Fn getpriority
e0304aa6	30	call and set with the
931b8415	31	.Fn setpriority
e0304aa6	32	call.
931b8415 CL	33	.Fa Which
	34	is one of
	35	.Dv PRIO_PROCESS ,
	36	.Dv PRIO_PGRP ,
	37	or
	38	.Dv PRIO_USER ,
	39	and
	40	.Fa who
e0304aa6	41	is interpreted relative to
931b8415 CL	42	.Fa which
	43	(a process identifier for
	44	.Dv PRIO_PROCESS ,
	45	process group
	46	identifier for
	47	.Dv PRIO_PGRP ,
	48	and a user ID for
	49	.Dv PRIO_USER ) .
f5c144bd	50	A zero value of
931b8415	51	.Fa who
f5c144bd	52	denotes the current process, process group, or user.
931b8415 CL	53	.Fa Prio
931b8415 CL	54	is a value in the range -20 to 20. The default priority is 0;
e0304aa6	55	lower priorities cause more favorable scheduling.
931b8415	56	.Pp
e0304aa6	57	The
931b8415	58	.Fn getpriority
e0304aa6 KM	59	call returns the highest priority (lowest numerical value)
e0304aa6 KM	60	enjoyed by any of the specified processes. The
931b8415	61	.Fn setpriority
e0304aa6 KM	62	call sets the priorities of all of the specified processes
e0304aa6 KM	63	to the specified value. Only the super-user may lower priorities.
931b8415	64	.Sh RETURN VALUES
e0304aa6	65	Since
931b8415 CL	66	.Fn getpriority
	67	can legitimately return the value -1, it is necessary
	68	to clear the external variable
	69	.Va errno
	70	prior to the
e0304aa6	71	call, then check it afterward to determine
931b8415	72	if a -1 is an error or a legitimate value.
e0304aa6	73	The
931b8415	74	.Fn setpriority
e0304aa6	75	call returns 0 if there is no error, or
931b8415 CL	76	-1 if there is.
	77	.Sh ERRORS
	78	.Fn Getpriority
e0304aa6	79	and
931b8415 CL	80	.Fn setpriority
	81	will fail if:
	82	.Bl -tag -width Er
	83	.It Bq Er ESRCH
9b8a2ecf	84	No process was located using the
931b8415	85	.Fa which
e0304aa6	86	and
931b8415	87	.Fa who
e0304aa6	88	values specified.
931b8415 CL	89	.It Bq Er EINVAL
	90	.Fa Which
	91	was not one of
	92	.Dv PRIO_PROCESS ,
	93	.Dv PRIO_PGRP ,
	94	or
	95	.Dv PRIO_USER .
	96	.El
	97	.Pp
	98	.Bl -tag -width Er
e0304aa6	99	In addition to the errors indicated above,
931b8415 CL	100	.Fn setpriority
	101	will fail if:
	102	.It Bq Er EPERM
e0304aa6 KM	103	A process was located, but neither its effective nor real user
e0304aa6 KM	104	ID matched the effective user ID of the caller.
931b8415	105	.It Bq Er EACCES
9b8a2ecf	106	A non super-user attempted to lower a process priority.
931b8415 CL	107	.El
	108	.Sh SEE ALSO
	109	.Xr nice 1 ,
	110	.Xr fork 2 ,
	111	.Xr renice 8
	112	.Sh HISTORY
	113	The
	114	.Nm
	115	function call appeared in
	116	.Bx 4.2 .