[apple/xnu.git] / bsd / man / man2 / getpriority.2

.\"	$NetBSD: getpriority.2,v 1.4 1995/02/27 12:33:15 cgd Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)getpriority.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.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
.Fn getpriority
function call appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: getpriority.2,v 1.4 1995/02/27 12:33:15 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt GETPRIORITY 2
	38	.Os BSD 4
	39	.Sh NAME
	40	.Nm getpriority ,
	41	.Nm setpriority
	42	.Nd get/set program scheduling priority
	43	.Sh SYNOPSIS
	44	.Fd #include <sys/time.h>
	45	.Fd #include <sys/resource.h>
	46	.Ft int
	47	.Fn getpriority "int which" "int who"
	48	.Ft int
	49	.Fn setpriority "int which" "int who" "int prio"
	50	.Sh DESCRIPTION
	51	The scheduling
	52	priority of the process, process group, or user, as indicated by
	53	.Fa which
	54	and
	55	.Fa who
	56	is obtained with the
	57	.Fn getpriority
	58	call and set with the
	59	.Fn setpriority
	60	call.
	61	.Fa Which
	62	is one of
	63	.Dv PRIO_PROCESS ,
	64	.Dv PRIO_PGRP ,
65	or
66	.Dv PRIO_USER ,
67	and
68	.Fa who
69	is interpreted relative to
70	.Fa which
71	(a process identifier for
72	.Dv PRIO_PROCESS ,
73	process group
74	identifier for
75	.Dv PRIO_PGRP ,
76	and a user ID for
77	.Dv PRIO_USER ) .
78	A zero value of
79	.Fa who
80	denotes the current process, process group, or user.
81	.Fa Prio
82	is a value in the range -20 to 20. The default priority is 0;
83	lower priorities cause more favorable scheduling.
84	.Pp
85	The
86	.Fn getpriority
87	call returns the highest priority (lowest numerical value)
88	enjoyed by any of the specified processes. The
89	.Fn setpriority
90	call sets the priorities of all of the specified processes
91	to the specified value. Only the super-user may lower priorities.
92	.Sh RETURN VALUES
93	Since
94	.Fn getpriority
95	can legitimately return the value -1, it is necessary
96	to clear the external variable
97	.Va errno
98	prior to the
99	call, then check it afterward to determine
100	if a -1 is an error or a legitimate value.
101	The
102	.Fn setpriority
103	call returns 0 if there is no error, or
104	-1 if there is.
105	.Sh ERRORS
106	.Fn Getpriority
107	and
108	.Fn setpriority
109	will fail if:
110	.Bl -tag -width Er
111	.It Bq Er ESRCH
112	No process was located using the
113	.Fa which
114	and
115	.Fa who
116	values specified.
117	.It Bq Er EINVAL
118	.Fa Which
119	was not one of
120	.Dv PRIO_PROCESS ,
121	.Dv PRIO_PGRP ,
122	or
123	.Dv PRIO_USER .
124	.El
125	.Pp
126	.Bl -tag -width Er
127	In addition to the errors indicated above,
128	.Fn setpriority
129	will fail if:
130	.It Bq Er EPERM
131	A process was located, but neither its effective nor real user
132	ID matched the effective user ID of the caller.
133	.It Bq Er EACCES
134	A non super-user attempted to lower a process priority.
135	.El
136	.Sh SEE ALSO
137	.Xr nice 1 ,
138	.Xr fork 2 ,
139	.Xr renice 8
140	.Sh HISTORY
141	The
142	.Fn getpriority
143	function call appeared in
144	.Bx 4.2 .