1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
.\" 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.
.\" 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
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dt GETPRIORITY 2
.Os
.Sh NAME
.Nm getpriority ,
.Nm setpriority
.Nd get/set program scheduling priority
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/time.h
.In 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
system call and set with the
.Fn setpriority
system call.
The
.Fa which
argument
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.
The
.Fa prio
argument
is a value in the range -20 to 20.
The default priority is 0;
lower priorities cause more favorable scheduling.
.Pp
The
.Fn getpriority
system call returns the highest priority (lowest numerical value)
enjoyed by any of the specified processes.
The
.Fn setpriority
system 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.
.Pp
.Rv -std setpriority
.Sh ERRORS
The
.Fn getpriority
and
.Fn setpriority
system calls
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
The
.Fa which
argument
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
system call appeared in
.Bx 4.2 .
|
