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Add man pages for the SYSV shm* and sem* functions.

Browse source 
This partially closes PR # docs/177.
This should probably also go into 2.1.

Submitted by:	daveho@infocom.com (David Hovemeyer)
This commit is contained in:
Joerg Wunsch 1995-10-03 19:17:21 +00:00
parent e79adb8ed6
commit 5f5555b1ea
7 changed files with 890 additions and 1 deletions
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5
lib/libc/sys/Makefile.inc
View file

@ -94,9 +94,11 @@ MAN2+= sys/accept.2 sys/access.2 sys/acct.2 sys/adjtime.2 sys/bind.2 \
sys/nfssvc.2 sys/open.2 sys/pathconf.2 sys/pipe.2 sys/profil.2 \
sys/quotactl.2 sys/read.2 sys/readlink.2 sys/reboot.2 sys/recv.2 \
sys/rename.2 sys/revoke.2 sys/rmdir.2 sys/rtprio.2 sys/select.2 \
sys/semctl.2 sys/semget.2 sys/semop.2 \
sys/send.2 sys/setgroups.2 \
sys/setpgid.2 sys/setregid.2 sys/setreuid.2 \
sys/setsid.2 sys/setuid.2 sys/shutdown.2 \
sys/setsid.2 sys/setuid.2 sys/shmat.2 sys/shmctl.2 sys/shmget.2 \
sys/shutdown.2 \
sys/sigaction.2 sys/sigpending.2 sys/sigprocmask.2 sys/sigreturn.2 \
sys/sigaltstack.2 sys/sigstack.2 sys/sigsuspend.2 sys/socket.2 \
sys/socketpair.2 sys/stat.2 sys/statfs.2 sys/swapon.2 sys/symlink.2 \
@ -130,6 +132,7 @@ MLINKS+=recv.2 recvfrom.2 recv.2 recvmsg.2
MLINKS+=send.2 sendmsg.2 send.2 sendto.2
MLINKS+=setpgid.2 setpgrp.2
MLINKS+=setuid.2 setegid.2 setuid.2 seteuid.2 setuid.2 setgid.2
MLINKS+=shmat.2 shmdt.2
MLINKS+=stat.2 fstat.2 stat.2 lstat.2
MLINKS+=statfs.2 fstatfs.2
MLINKS+=syscall.2 __syscall.2

173
lib/libc/sys/semctl.2 Normal file
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@ -0,0 +1,173 @@
.\"
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $Id$
.\"
.Dd September 12, 1995
.Dt SEMCTL 2
.Os FreeBSD
.Sh NAME
.Nm semctl
.Nd control operations on a semaphore set
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Fd #include <sys/sem.h>
.Ft int
.Fn "semctl" "int semid" "int semnum" "int cmd" "union semun arg"
.Sh DESCRIPTION
.Fn Semctl
performs the operation indicated by
.Fa cmd
on the semaphore set indicated by
.Fa semid .
For the commands that use the
.Fa arg
parameter,
.Fa "union semun"
is defined as follows:
.Bd -literal
.\"
.\" From <sys/sem.h>:
.\"
union semun {
int val; /* value for SETVAL */
struct semid_ds *buf; /* buffer for IPC_STAT & IPC_SET */
u_short *array; /* array for GETALL & SETALL */
};
.Ed
.Pp
Commands are performed as follows:
.\"
.\" This section based on Stevens, _Advanced Programming in the UNIX
.\" Environment_.
.\"
.Bl -tag -width IPC_RMIDXXX
.It Dv IPC_STAT
Fetch the semaphore set's
.Fa "struct semid_ds" ,
storing it in the memory pointed to by
.Fa arg.buf .
.It Dv IPC_SET
Changes the
.Fa sem_perm.uid ,
.Fa sem_perm.gid ,
and
.Fa sem_perm.mode
members of the semaphore set's
.Fa "struct semid_ds"
to match those of the struct pointed to by
.Fa arg.buf .
The calling process's effective uid must
match either
.Fa sem_perm.uid
or
.Fa sem_perm.cuid ,
or it must have superuser privileges.
.It IPC_RMID
Immediately removes the semaphore set from the system. The calling
process's effictive uid must equal the semaphore set's
.Fa sem_perm.uid
or
.Fa sem_perm.cuid ,
or the process must have superuser priviliges.
.It Dv GETVAL
Return the value of semaphore number
.Fa semnum .
.It Dv SETVAL
Set the value of semaphore number
.Fa semnum
to
.Fa arg.val .
.It Dv GETPID
Return the pid of the last process to perform an operation on
semaphore number
.Fa semnum .
.It Dv GETNCNT
Return the number of processes waiting for semaphore number
.Fa semnum Ns 's
value to become greater than its current value.
.It Dv GETZCNT
Return the number of processes waiting for semaphore number
.Fa semnum Ns 's
value to become 0.
.It Dv GETALL
Fetch the value of all of the semaphores in the set into the
array pointed to by
.Fa arg.array .
.It Dv SETALL
Set the values of all of the semaphores in the set to the values
in the array pointed to by
.Fa arg.array .
.El
.Pp
The
.Fa "struct semid_ds"
is defined as follows:
.Bd -literal
.\"
.\" Taken straight from <sys/sem.h>.
.\"
struct semid_ds {
struct ipc_perm sem_perm; /* operation permission struct */
struct sem *sem_base; /* pointer to first semaphore in set */
u_short sem_nsems; /* number of sems in set */
time_t sem_otime; /* last operation time */
long sem_pad1; /* SVABI/386 says I need this here */
time_t sem_ctime; /* last change time */
/* Times measured in secs since */
/* 00:00:00 GMT, Jan. 1, 1970 */
long sem_pad2; /* SVABI/386 says I need this here */
long sem_pad3[4]; /* SVABI/386 says I need this here */
};
.Ed
.Sh RETURN VALUES
On success, when
.Fa cmd
is one of GETVAL, GETNCNT, or GETZCNT,
.Fn semctl
returns the corresponding value; otherwise, 0 is returned.
On failure, -1 is returned, and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Semctl
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
No semaphore set corresponds to
.Fa semid .
.It Bq Er EINVAL
.Fa semnum
is not in the range of valid semaphores for given semaphore set.
.It Bq Er EPERM
The calling process's effective uid does not match the uid of
the semaphore set's owner or creator.
.It Bq Er EACCES
Permission denied due to mismatch between operation and mode of
semaphore set.
.Sh SEE ALSO
.Xr semget 2 ,
.Xr semop 2

137
lib/libc/sys/semget.2 Normal file
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@ -0,0 +1,137 @@
.\"
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $Id$
.\"
.Dd September 12, 1995
.Dt SEMGET 2
.Os FreeBSD
.Sh NAME
.Nm semget
.Nd obtain a semaphore id
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Fd #include <sys/sem.h>
.Ft int
.Fn "semget" "key_t key" "int nsems" "int flag"
.Sh DESCRIPTION
Based on the values of
.Fa key
and
.Fa flag ,
.Fn semget
returns the identifier of a newly created or previously existing
set of semaphores.
.\"
.\" This is copied verbatim from the shmget manpage. Perhaps
.\" it should go in a common manpage, such as .Xr ipc 2
.\"
The key
is analogous to a filename: it provides a handle that names an
IPC object. There are three ways to specify a key:
.Bl -bullet
.It
IPC_PRIVATE may be specified, in which case a new IPC object
will be created.
.It
An integer constant may be specified. If no IPC object corresponding
to
.Fa key
is specified and the IPC_CREAT bit is set in
.Fa flag ,
a new one will be created.
.It
.Fn ftok
may be used to generate a key from a pathname. See
.Xr ftok 3 .
.El
.\"
.\" Likewise for this section, except SHM_* becomes SEM_*.
.\"
.Pp
The mode of a newly created IPC object is determined by
.Em OR Ns 'ing
the following constants into the
.Fa flag
parameter:
.Bl -tag -width XSEM_WXX6XXX
.It Dv SEM_R
Read access for user.
.It Dv SEM_W
Write access for user.
.It Dv (SEM_R>>3)
Read access for group.
.It Dv (SEM_W>>3)
Write access for group.
.It Dv (SEM_R>>6)
Read access for other.
.It Dv (SEM_W>>6)
Write access for other.
.El
.Pp
If a new set of semaphores is being created,
.Fa nsems
is used to indicate the number of semaphores the set should contain.
Otherwise,
.Fa nsems
may be specified as 0.
.Sh RETURN VALUES
.Fn Semget
returns the id of a semaphore set if successful; otherwise, -1
is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Semget
will fail if:
.Bl -tag -width Er
.\" ipcperm could fail (we're opening to read and write, as it were)
.It Bq Er EACCES
Access permission failure.
.\"
.\" sysv_sem.c is quite explicit about these, so I'm pretty sure
.\" this is accurate
.\"
.It Bq Er EEXIST
IPC_CREAT and IPC_EXCL were specified, and a semaphore set
corresponding to
.Fa key
already exists.
.It Bq Er EINVAL
The number of semaphores requested exceeds the system imposed maximum
per set.
.It Bq Er ENOSPC
Insufficiently many semaphores are available.
.It Bq Er ENOSPC
The kernel could not allocate a
.Fa "struct semid_ds" .
.It Bq Er ENOENT
No semaphore set was found corresponding to
.Fa key ,
and IPC_CREAT was not specified.
.Sh SEE ALSO
.Xr semctl 2 ,
.Xr semop 2

192
lib/libc/sys/semop.2 Normal file
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@ -0,0 +1,192 @@
.\"
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $Id$
.\"
.Dd September 22, 1995
.Dt SEMOP 2
.Os FreeBSD
.Sh NAME
.Nm semop
.Nd atomic array of operations on a semaphore set
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Fd #include <sys/sem.h>
.Ft int
.Fn "semop" "int semid" "struct sembuf array[]" "unsigned nops"
.Sh DESCRIPTION
.Fn Semop
atomically performs the array of operations indicated by
.Fa array
on the semaphore set indicated by
.Fa semid .
The length of
.Fa array
is indicated by
.Fa nops .
Each operation is encoded in a
.Fa "struct sembuf" ,
which is defined as follows:
.Bd -literal
.\"
.\" From <sys/sem.h>
.\"
struct sembuf {
u_short sem_num; /* semaphore # */
short sem_op; /* semaphore operation */
short sem_flg; /* operation flags */
};
.Ed
.Pp
For each element in
.Fa array ,
.Fa sem_op
and
.Fa sem_flg
determine an operation to be performed on semaphore number
.Fa sem_num
in the set. The values SEM_UNDO and IPC_NOWAIT may be
.Em OR Ns 'ed
into the
.Fa sem_flg
member in order to modify the behavior of the given operation.
.Pp
The operation performed depends as follows on the value of
.Fa sem_op :
.\"
.\" This section is based on the description of semop() in
.\" Stevens, _Advanced Programming in the UNIX Environment_.
.\"
.Bl -bullet
.It
When
.Fa sem_op
is positive, the semaphore's value is incremented by
.Fa sem_op Ns 's
value. If SEM_UNDO is specified, the semaphore's adjust on exit
value is decremented by
.Fa sem_op Ns 's
value. A positive value for
.Fa sem_op
generally corresponds to a process releasing a resource
associated with the semaphore.
.It
The behavior when
.Fa sem_op
is negative depends on the current value of the semaphore:
.Bl -bullet
.It
If the current value of the semaphore is greater than or equal to
the absolute value of
.Fa sem_op ,
then the value is decremented by the absolute value of
.Fa sem_op .
If SEM_UNDO is specified, the semaphore's adjust on exit
value is incremented by the absolute value of
.Fa sem_op .
.It
If the current value of the semaphore is less than
.Fa sem_op Ns 's
value, one of the following happens:
.\" XXX a *second* sublist?
.Bl -bullet
.It
If IPC_NOWAIT was specifed, then
.Fn semop
returns immediately with a return value of EAGAIN.
.It
If some other process has removed the semaphore with the IPC_RMID
option of
.Fn semctl ,
then
.Fn semop
returns immediately with a return value of EINVAL.
.It
Otherwise, the calling process is put to sleep until the semaphore's
value is greater than or equal to the absolute value of
.Fa sem_op .
When this condition becomes true, the semaphore's value is decremented
by the absolute value of
.Fa sem_op ,
and the semaphore's adjust on exit value is incremented by the
absolute value of
.Fa sem_op .
.El
.Pp
A negative value for
.Fa sem_op
generally means that a process is waiting for a resource to become
available.
.El
.Pp
.It
When
.Fa sem_op
is zero, the process waits for the semaphore's value to become zero.
If it is already zero, the call to
.Fn semop
can return immediately. Otherwise, the calling process is put to
sleep until the semaphore's value becomes zero.
.El
.Pp
For each semaphore a process has in use, the kernel maintains an
`adjust on exit' value, as alluded to earlier. When a process
exits, either voluntarily or involuntarily, the adjust on exit value
for each semaphore is added to the semaphore's value. This can
be used to insure that a resource is released if a process terminates
unexpectedly.
.Sh RETURN VALUES
On success,
.Fn semop
returns 0; otherwise, -1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Semop
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
No semaphore set corresponds to
.Fa semid .
.It Bq Er EACCES
Permission denied due to mismatch between operation and mode of
semaphore set.
.It Bq Er EAGAIN
The semaphore's value was less than
.Fa sem_op ,
and IPC_NOWAIT was specified.
.It Bq Er E2BIG
Too many operations were specified.
.It Bq Er EFBIG
.\"
.\" I'd have thought this would be EINVAL, but the source says
.\" EFBIG.
.\"
.Fa sem_num
was not in the range of valid semaphores for the set.
.Sh SEE ALSO
.Xr semget 2 ,
.Xr semctl 2

110
lib/libc/sys/shmat.2 Normal file
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@ -0,0 +1,110 @@
.\"
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $Id$
.\"
.Dd August 2, 1995
.Dt SHMAT 2
.Os FreeBSD
.Sh NAME
.Nm shmat ,
.Nm shmdt
.Nd attach or detach shared memory
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Fd #include <sys/shm.h>
.Ft void *
.Fn "shmat" "int shmid" "void *addr" "int flag"
.Ft int
.Fn "shmdt" "void *addr"
.Sh DESCRIPTION
.Fn Shmat
attaches the shared memory segment identifed by
.Fa shmid
to the calling process's address space. The address where the segment
is attached is determined as follows:
.\"
.\" These are cribbed almost exactly from Stevens, _Advanced Programming in
.\" the UNIX Environment_.
.\"
.Bl -bullet
.It
If
.Fa addr
is 0, the segment is attached at an address selected by the
kernel.
.It
If
.Fa addr
is nonzero and SHM_RND is not specifed in
.Fa flag ,
the segment is attached the specified address.
.It
If
.Fa addr
is specified and SHM_RND is specified,
.Fa addr
is rounded down to the nearest multiple of SHMLBA.
.El
.Pp
.Fn Shmdt
detaches the shared memory segment at the address specified by
.Fa addr
from the calling process's address space.
.Sh RETURN VALUES
Upon success,
.Fn shmat
returns the address where the segment is attached; otherwise, -1
is returned and
.Va errno
is set to indicate the error.
.Pp
Upon success,
.Fn shmdt
returns 0; otherwise, -1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Shmat
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
No shared memory segment was found corresponding to
.Fa shmid .
.It Bq Er EINVAL
.Fa addr
was not an acceptable address.
.El
.Pp
.Fn Shmdt
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
.Fa addr
does not point to a shared memory segment.
.Sh "SEE ALSO"
.Xr shmget 2 ,
.Xr shmctl 2

136
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@ -0,0 +1,136 @@
.\"
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $Id$
.\"
.Dd July 17, 1995
.Dt SHMCTL 2
.Os FreeBSD
.Sh NAME
.Nm shmctl
.Nd shared memory control
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Fd #include <sys/shm.h>
.Ft int
.Fn "shmctl" "int shmid" "int cmd" "struct shmid_ds *buf"
.Sh DESCRIPTION
Performs the action specified by
.Fa cmd
on the shared memory segment identified by
.Fa shmid :
.Bl -tag -width SHM_UNLOCKX
.It Dv IPC_STAT
Fetch the segment's
.Fa "struct shmid_ds" ,
storing it in the memory pointed to by
.Fa buf .
.\"
.\" XXX need to make sure that this is correct for FreeBSD
.\"
.It Dv IPC_SET
Changes the
.Fa shm_perm.uid ,
.Fa shm_perm.gid ,
and
.Fa shm_perm.mode
members of the segment's
.Fa "struct shmid_ds"
to match those of the struct pointed to by
.Fa buf .
The calling process's effective uid must
match either
.Fa shm_perm.uid
or
.Fa shm_perm.cuid ,
or it must have superuser privileges.
.It Dv IPC_RMID
Removes the segment from the system. The removal will not take
effect until all processes having attached the segment have exited;
however, once the IPC_RMID operation has taken place, no further
processes will be allowed to attach the segment. For the operation
to succeed, the calling process's effective uid must match
.Fa shm_perm.uid
or
.Fa shm_perm.cuid ,
or the process must have superuser privilges.
.\" .It Dv SHM_LOCK
.\" Locks the segment in memory. The calling process must have
.\" superuser privileges. Not implemented in FreeBSD.
.\" .It Dv SHM_UNLOCK
.\" Unlocks the segment from memory. The calling process must
.\" have superuser priviliges. Not implemented in FreeBSD.
.El
.Pp
The
.Fa "shmid_ds"
struct is defined as follows:
.\"
.\" I fiddled with the spaces a bit to make it fit well when viewed
.\" with nroff, but otherwise it's straight from sys/shm.h
.\"
.Bd -literal
struct shmid_ds {
struct ipc_perm shm_perm; /* operation permission structure */
int shm_segsz; /* size of segment in bytes */
pid_t shm_lpid; /* process ID of last shared memory op */
pid_t shm_cpid; /* process ID of creator */
short shm_nattch; /* number of current attaches */
time_t shm_atime; /* time of last shmat() */
time_t shm_dtime; /* time of last shmdt() */
time_t shm_ctime; /* time of last change by shmctl() */
void *shm_internal; /* sysv stupidity */
};
.Ed
.Sh RETURN VALUES
Upon successful completion,
.Fn shmctl
returns 0. Otherwise, it returns -1 and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn Shmctl
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid operation, or
no shared memory segment was found corresponding to
.Fa shmid .
.\"
.\" XXX I think the following is right: ipcperm() only returns EPERM
.\" when an attempt is made to modify (IPC_M) by a non-creator
.\" non-owner
.It Bq Er EPERM
The calling process's effective uid does not match the uid of
the shared memory segment's owner or creator.
.It Bq Er EACCES
Permission denied due to mismatch between operation and mode of
shared memory segment.
.Sh "SEE ALSO"
.Xr shmget 2 ,
.Xr shmat 2 ,
.Xr shmdt 2 ,
.Xr ftok 3

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.\"
.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com>
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $Id$
.\"
.Dd July 3, 1995
.Dt SHMGET 2
.Os FreeBSD
.Sh NAME
.Nm shmget
.Nd obtain a shared memory identifier
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/ipc.h>
.Fd #include <sys/shm.h>
.Ft int
.Fn "shmget" "key_t key" "int size" "int flag"
.Sh DESCRIPTION
Based on the values of
.Fa key
and
.Fa flag ,
.Fn shmget
returns the identifier of a newly created or previously existing shared
memory segment.
.\"
.\" The following bit about keys and modes also applies to semaphores
.\" and message queues.
.\"
The key
is analogous to a filename: it provides a handle that names an
IPC object. There are three ways to specify a key:
.Bl -bullet
.It
IPC_PRIVATE may be specified, in which case a new IPC object
will be created.
.It
An integer constant may be specified. If no IPC object corresponding
to
.Fa key
is specified and the IPC_CREAT bit is set in
.Fa flag ,
a new one will be created.
.It
.Fn ftok
may be used to generate a key from a pathname. See
.Xr ftok 3 .
.El
.Pp
The mode of a newly created IPC object is determined by
.Em OR Ns 'ing
the following constants into the
.Fa flag
parameter:
.Bl -tag -width XSHM_WXX6XXX
.It Dv SHM_R
Read access for user.
.It Dv SHM_W
Write access for user.
.It Dv (SHM_R>>3)
Read access for group.
.It Dv (SHM_W>>3)
Write access for group.
.It Dv (SHM_R>>6)
Read access for other.
.It Dv (SHM_W>>6)
Write access for other.
.El
.\"
.\" XXX - we should also mention how uid, euid, and gid affect ownership
.\" and use
.\"
.\" end section about keys and modes
.\"
.Pp
When creating a new shared memory segment,
.Fa size
indicates the desired size of the new segment in bytes. The size
of the segment may be rounded up to a multiple convenient to the
kernel (i.e., the page size).
.Sh RETURN VALUES
Upon successful completion,
.Fn shmget
returns the positive integer identifier of a shared memory segment.
Otherwise, -1 is returned and
.Va errno
set to indicate the error.
.Sh ERRORS
.Fn Shmget
will fail if:
.Bl -tag -width Er
.\"
.\" XXX What about ipcperm failing?
.\"
.It Bq Er EINVAL
Size specified is greater than the size of the previously existing segment.
Size specified is less than the system imposed minumum, or greater than
the system imposed maximum.
.It Bq Er ENOENT
No shared memory segment was found matching
.Fa key ,
and IPC_CREAT was not specified.
.It Bq Er ENOSPC
The kernel was unable to allocate enough memory to
satisfy the request.
.It Bq Er EEXIST
IPC_CREAT and IPC_EXCL were specified, and a shared memory segment
corresponding to
.Fa key
already exists.
.Pp
.Sh "SEE ALSO"
.Xr shmctl 2 ,
.Xr shmat 2 ,
.Xr shmdt 2 ,
.Xr ftok 3