1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
174 lines
5.1 KiB
Groff
174 lines
5.1 KiB
Groff
.\"
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.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
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.\"
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 12, 1995
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.Dt SEMCTL 2
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.Os FreeBSD
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.Sh NAME
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.Nm semctl
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.Nd control operations on a semaphore set
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/ipc.h>
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.Fd #include <sys/sem.h>
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.Ft int
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.Fn "semctl" "int semid" "int semnum" "int cmd" "union semun arg"
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.Sh DESCRIPTION
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.Fn Semctl
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performs the operation indicated by
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.Fa cmd
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on the semaphore set indicated by
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.Fa semid .
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For the commands that use the
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.Fa arg
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parameter,
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.Fa "union semun"
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is defined as follows:
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.Bd -literal
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.\"
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.\" From <sys/sem.h>:
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.\"
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union semun {
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int val; /* value for SETVAL */
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struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
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u_short *array; /* array for GETALL & SETALL */
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};
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.Ed
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.Pp
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Commands are performed as follows:
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.\"
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.\" This section based on Stevens, _Advanced Programming in the UNIX
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.\" Environment_.
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.\"
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.Bl -tag -width IPC_RMIDXXX
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.It Dv IPC_STAT
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Fetch the semaphore set's
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.Fa "struct semid_ds" ,
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storing it in the memory pointed to by
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.Fa arg.buf .
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.It Dv IPC_SET
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Changes the
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.Fa sem_perm.uid ,
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.Fa sem_perm.gid ,
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and
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.Fa sem_perm.mode
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members of the semaphore set's
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.Fa "struct semid_ds"
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to match those of the struct pointed to by
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.Fa arg.buf .
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The calling process's effective uid must
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match either
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.Fa sem_perm.uid
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or
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.Fa sem_perm.cuid ,
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or it must have superuser privileges.
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.It IPC_RMID
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Immediately removes the semaphore set from the system. The calling
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process's effective uid must equal the semaphore set's
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.Fa sem_perm.uid
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or
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.Fa sem_perm.cuid ,
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or the process must have superuser privileges.
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.It Dv GETVAL
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Return the value of semaphore number
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.Fa semnum .
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.It Dv SETVAL
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Set the value of semaphore number
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.Fa semnum
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to
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.Fa arg.val .
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.It Dv GETPID
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Return the pid of the last process to perform an operation on
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semaphore number
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.Fa semnum .
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.It Dv GETNCNT
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Return the number of processes waiting for semaphore number
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.Fa semnum Ns 's
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value to become greater than its current value.
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.It Dv GETZCNT
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Return the number of processes waiting for semaphore number
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.Fa semnum Ns 's
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value to become 0.
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.It Dv GETALL
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Fetch the value of all of the semaphores in the set into the
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array pointed to by
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.Fa arg.array .
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.It Dv SETALL
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Set the values of all of the semaphores in the set to the values
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in the array pointed to by
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.Fa arg.array .
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.El
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.Pp
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The
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.Fa "struct semid_ds"
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is defined as follows:
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.Bd -literal
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.\"
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.\" Taken straight from <sys/sem.h>.
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.\"
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struct semid_ds {
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struct ipc_perm sem_perm; /* operation permission struct */
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struct sem *sem_base; /* pointer to first semaphore in set */
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u_short sem_nsems; /* number of sems in set */
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time_t sem_otime; /* last operation time */
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long sem_pad1; /* SVABI/386 says I need this here */
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time_t sem_ctime; /* last change time */
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/* Times measured in secs since */
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/* 00:00:00 GMT, Jan. 1, 1970 */
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long sem_pad2; /* SVABI/386 says I need this here */
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long sem_pad3[4]; /* SVABI/386 says I need this here */
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};
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.Ed
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.Sh RETURN VALUES
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On success, when
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.Fa cmd
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is one of GETVAL, GETNCNT, or GETZCNT,
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.Fn semctl
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returns the corresponding value; otherwise, 0 is returned.
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On failure, -1 is returned, and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn Semctl
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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No semaphore set corresponds to
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.Fa semid .
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.It Bq Er EINVAL
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.Fa semnum
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is not in the range of valid semaphores for given semaphore set.
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.It Bq Er EPERM
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The calling process's effective uid does not match the uid of
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the semaphore set's owner or creator.
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.It Bq Er EACCES
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Permission denied due to mismatch between operation and mode of
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semaphore set.
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.Sh SEE ALSO
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.Xr semget 2 ,
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.Xr semop 2
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