1.\"
2.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
3.\"
4.\" 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.\"
15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25.\"
26.\" $FreeBSD: head/lib/libc/sys/semctl.2 108087 2002-12-19 09:40:28Z ru $
27.\"
28.Dd September 12, 1995
29.Dt SEMCTL 2
30.Os
31.Sh NAME
32.Nm semctl
33.Nd control operations on a semaphore set
34.Sh LIBRARY
35.Lb libc
36.Sh SYNOPSIS
37.In sys/types.h
38.In sys/ipc.h
39.In sys/sem.h
40.Ft int
41.Fn semctl "int semid" "int semnum" "int cmd" ...
42.Sh DESCRIPTION
43The
44.Fn semctl
45system call
46performs the operation indicated by
47.Fa cmd
48on the semaphore set indicated by
49.Fa semid .
50A fourth argument, a
51.Fa "union semun arg" ,
52is required for certain values of
53.Fa cmd .
54For the commands that use the
55.Fa arg
56argument,
57.Fa "union semun"
58is defined as follows:
59.Bd -literal
60.\"
61.\" From <sys/sem.h>:
62.\"
63union semun {
64 int val; /* value for SETVAL */
65 struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
66 u_short *array; /* array for GETALL & SETALL */
67};
68.Ed
69.Pp
70Commands are performed as follows:
71.\"
72.\" This section based on Stevens, _Advanced Programming in the UNIX
73.\" Environment_.
74.\"
75.Bl -tag -width IPC_RMIDXXX
76.It Dv IPC_STAT
77Fetch the semaphore set's
78.Fa "struct semid_ds" ,
79storing it in the memory pointed to by
80.Fa arg.buf .
81.It Dv IPC_SET
82Changes the
83.Fa sem_perm.uid ,
84.Fa sem_perm.gid ,
85and
86.Fa sem_perm.mode
87members of the semaphore set's
88.Fa "struct semid_ds"
89to match those of the struct pointed to by
90.Fa arg.buf .
91The calling process's effective uid must
92match either
93.Fa sem_perm.uid
94or
95.Fa sem_perm.cuid ,
96or it must have superuser privileges.
97.It IPC_RMID
98Immediately removes the semaphore set from the system. The calling
99process's effective uid must equal the semaphore set's
100.Fa sem_perm.uid
101or
102.Fa sem_perm.cuid ,
103or the process must have superuser privileges.
104.It Dv GETVAL
105Return the value of semaphore number
106.Fa semnum .
107.It Dv SETVAL
108Set the value of semaphore number
109.Fa semnum
110to
111.Fa arg.val .
112Outstanding adjust on exit values for this semaphore in any process
113are cleared.
114.It Dv GETPID
115Return the pid of the last process to perform an operation on
116semaphore number
117.Fa semnum .
118.It Dv GETNCNT
119Return the number of processes waiting for semaphore number
120.Fa semnum Ns 's
121value to become greater than its current value.
122.It Dv GETZCNT
123Return the number of processes waiting for semaphore number
124.Fa semnum Ns 's
125value to become 0.
126.It Dv GETALL
127Fetch the value of all of the semaphores in the set into the
128array pointed to by
129.Fa arg.array .
130.It Dv SETALL
131Set the values of all of the semaphores in the set to the values
132in the array pointed to by
133.Fa arg.array .
134Outstanding adjust on exit values for all semaphores in this set,
135in any process are cleared.
136.El
137.Pp
138The
139.Vt "struct semid_ds"
140is defined as follows:
141.Bd -literal
142.\"
143.\" Taken straight from <sys/sem.h>.
144.\"
145struct semid_ds {
146 struct ipc_perm sem_perm; /* operation permission struct */
147 struct sem *sem_base; /* pointer to first semaphore in set */
148 u_short sem_nsems; /* number of sems in set */
149 time_t sem_otime; /* last operation time */
150 long sem_pad1; /* SVABI/386 says I need this here */
151 time_t sem_ctime; /* last change time */
152 /* Times measured in secs since */
153 /* 00:00:00 GMT, Jan. 1, 1970 */
154 long sem_pad2; /* SVABI/386 says I need this here */
155 long sem_pad3[4]; /* SVABI/386 says I need this here */
156};
157.Ed
158.Sh RETURN VALUES
159On success, when
160.Fa cmd
161is one of
162.Dv GETVAL , GETPID , GETNCNT
163or
164.Dv GETZCNT ,
165.Fn semctl
166returns the corresponding value; otherwise, 0 is returned.
167On failure, -1 is returned, and
168.Va errno
169is set to indicate the error.
170.Sh ERRORS
171The
172.Fn semctl
173system call
174will fail if:
175.Bl -tag -width Er
176.It Bq Er EINVAL
177No semaphore set corresponds to
178.Fa semid .
179.It Bq Er EINVAL
180The
181.Fa semnum
182argument
183is not in the range of valid semaphores for given semaphore set.
184.It Bq Er EPERM
185The calling process's effective uid does not match the uid of
186the semaphore set's owner or creator.
187.It Bq Er EACCES
188Permission denied due to mismatch between operation and mode of
189semaphore set.
190.It Bq Er ERANGE
191.Dv SETVAL
192or
193.Dv SETALL
194attempted to set a semaphore outside the allowable range
195.Bq 0 .. Dv SEMVMX .
196.El
197.Sh SEE ALSO
198.Xr semget 2 ,
199.Xr semop 2
200.Sh BUGS
201.Dv SETALL
202may update some semaphore elements before returning an error.
2.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
3.\"
4.\" 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.\"
15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25.\"
26.\" $FreeBSD: head/lib/libc/sys/semctl.2 108087 2002-12-19 09:40:28Z ru $
27.\"
28.Dd September 12, 1995
29.Dt SEMCTL 2
30.Os
31.Sh NAME
32.Nm semctl
33.Nd control operations on a semaphore set
34.Sh LIBRARY
35.Lb libc
36.Sh SYNOPSIS
37.In sys/types.h
38.In sys/ipc.h
39.In sys/sem.h
40.Ft int
41.Fn semctl "int semid" "int semnum" "int cmd" ...
42.Sh DESCRIPTION
43The
44.Fn semctl
45system call
46performs the operation indicated by
47.Fa cmd
48on the semaphore set indicated by
49.Fa semid .
50A fourth argument, a
51.Fa "union semun arg" ,
52is required for certain values of
53.Fa cmd .
54For the commands that use the
55.Fa arg
56argument,
57.Fa "union semun"
58is defined as follows:
59.Bd -literal
60.\"
61.\" From <sys/sem.h>:
62.\"
63union semun {
64 int val; /* value for SETVAL */
65 struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
66 u_short *array; /* array for GETALL & SETALL */
67};
68.Ed
69.Pp
70Commands are performed as follows:
71.\"
72.\" This section based on Stevens, _Advanced Programming in the UNIX
73.\" Environment_.
74.\"
75.Bl -tag -width IPC_RMIDXXX
76.It Dv IPC_STAT
77Fetch the semaphore set's
78.Fa "struct semid_ds" ,
79storing it in the memory pointed to by
80.Fa arg.buf .
81.It Dv IPC_SET
82Changes the
83.Fa sem_perm.uid ,
84.Fa sem_perm.gid ,
85and
86.Fa sem_perm.mode
87members of the semaphore set's
88.Fa "struct semid_ds"
89to match those of the struct pointed to by
90.Fa arg.buf .
91The calling process's effective uid must
92match either
93.Fa sem_perm.uid
94or
95.Fa sem_perm.cuid ,
96or it must have superuser privileges.
97.It IPC_RMID
98Immediately removes the semaphore set from the system. The calling
99process's effective uid must equal the semaphore set's
100.Fa sem_perm.uid
101or
102.Fa sem_perm.cuid ,
103or the process must have superuser privileges.
104.It Dv GETVAL
105Return the value of semaphore number
106.Fa semnum .
107.It Dv SETVAL
108Set the value of semaphore number
109.Fa semnum
110to
111.Fa arg.val .
112Outstanding adjust on exit values for this semaphore in any process
113are cleared.
114.It Dv GETPID
115Return the pid of the last process to perform an operation on
116semaphore number
117.Fa semnum .
118.It Dv GETNCNT
119Return the number of processes waiting for semaphore number
120.Fa semnum Ns 's
121value to become greater than its current value.
122.It Dv GETZCNT
123Return the number of processes waiting for semaphore number
124.Fa semnum Ns 's
125value to become 0.
126.It Dv GETALL
127Fetch the value of all of the semaphores in the set into the
128array pointed to by
129.Fa arg.array .
130.It Dv SETALL
131Set the values of all of the semaphores in the set to the values
132in the array pointed to by
133.Fa arg.array .
134Outstanding adjust on exit values for all semaphores in this set,
135in any process are cleared.
136.El
137.Pp
138The
139.Vt "struct semid_ds"
140is defined as follows:
141.Bd -literal
142.\"
143.\" Taken straight from <sys/sem.h>.
144.\"
145struct semid_ds {
146 struct ipc_perm sem_perm; /* operation permission struct */
147 struct sem *sem_base; /* pointer to first semaphore in set */
148 u_short sem_nsems; /* number of sems in set */
149 time_t sem_otime; /* last operation time */
150 long sem_pad1; /* SVABI/386 says I need this here */
151 time_t sem_ctime; /* last change time */
152 /* Times measured in secs since */
153 /* 00:00:00 GMT, Jan. 1, 1970 */
154 long sem_pad2; /* SVABI/386 says I need this here */
155 long sem_pad3[4]; /* SVABI/386 says I need this here */
156};
157.Ed
158.Sh RETURN VALUES
159On success, when
160.Fa cmd
161is one of
162.Dv GETVAL , GETPID , GETNCNT
163or
164.Dv GETZCNT ,
165.Fn semctl
166returns the corresponding value; otherwise, 0 is returned.
167On failure, -1 is returned, and
168.Va errno
169is set to indicate the error.
170.Sh ERRORS
171The
172.Fn semctl
173system call
174will fail if:
175.Bl -tag -width Er
176.It Bq Er EINVAL
177No semaphore set corresponds to
178.Fa semid .
179.It Bq Er EINVAL
180The
181.Fa semnum
182argument
183is not in the range of valid semaphores for given semaphore set.
184.It Bq Er EPERM
185The calling process's effective uid does not match the uid of
186the semaphore set's owner or creator.
187.It Bq Er EACCES
188Permission denied due to mismatch between operation and mode of
189semaphore set.
190.It Bq Er ERANGE
191.Dv SETVAL
192or
193.Dv SETALL
194attempted to set a semaphore outside the allowable range
195.Bq 0 .. Dv SEMVMX .
196.El
197.Sh SEE ALSO
198.Xr semget 2 ,
199.Xr semop 2
200.Sh BUGS
201.Dv SETALL
202may update some semaphore elements before returning an error.