165 lines
4.3 KiB
Groff
165 lines
4.3 KiB
Groff
.\" $NetBSD: shmget.2,v 1.13 2001/09/16 02:13:31 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 1995 Frank van der Linden
|
|
.\" 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 for the NetBSD Project
|
|
.\" by Frank van der Linden
|
|
.\" 4. The name of the author may not be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
|
|
.\"
|
|
.Dd August 25, 1999
|
|
.Dt SHMGET 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm shmget
|
|
.Nd get shared memory segment
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/shm.h>
|
|
.Ft int
|
|
.Fn shmget "key_t key" "size_t size" "int shmflg"
|
|
.Sh DESCRIPTION
|
|
.Fn shmget
|
|
returns the shared memory identifier associated with the key
|
|
.Fa key .
|
|
The
|
|
.Fa shmflg
|
|
should be a combination of the following flags:
|
|
.Bl -tag -offset indent -width IPC_NOWAIT
|
|
.It Dv IPC_CREAT
|
|
create if segment does not exist
|
|
.It Dv IPC_EXCL
|
|
fail if segment already exists
|
|
.It Dv IPC_NOWAIT
|
|
return error instead of waiting
|
|
.El
|
|
.Pp
|
|
and nine bits of access bits, based on:
|
|
.Bl -tag -offset indent -width IPC_R
|
|
.It Dv IPC_R
|
|
read permission
|
|
.It Dv IPC_W
|
|
write permission
|
|
.It Dv IPC_M
|
|
changing control info permission
|
|
.El
|
|
.Pp
|
|
A shared memory segment is created if either
|
|
.Fa key
|
|
is equal to
|
|
.Dv IPC_PRIVATE ,
|
|
or
|
|
.Fa key
|
|
does not have a shared memory segment identifier associated with it, and the
|
|
.Dv IPC_CREAT
|
|
bit is set in
|
|
.Fa shmflg .
|
|
.Pp
|
|
If a new shared memory segment is created, the data structure
|
|
associated with it (the
|
|
.Va shmid_ds
|
|
structure, see
|
|
.Xr shmctl 2 )
|
|
is initialized as follows:
|
|
.Bl -bullet
|
|
.It
|
|
.Va shm_perm.cuid
|
|
and
|
|
.Va shm_perm.uid
|
|
are set to the effective uid of the calling process.
|
|
.It
|
|
.Va shm_perm.gid
|
|
and
|
|
.Va shm_perm.cgid
|
|
are set to the effective gid of the calling process.
|
|
.It
|
|
.Va shm_perm.mode
|
|
is set to the lower 9 bits of
|
|
.Fa shmflg .
|
|
.It
|
|
.Va shm_lpid ,
|
|
.Va shm_nattch ,
|
|
.Va shm_atime ,
|
|
and
|
|
.Va shm_dtime
|
|
are set to 0.
|
|
.It
|
|
.Va shm_ctime
|
|
is set to the current time.
|
|
.It
|
|
.Va shm_segsz
|
|
is set to the value of
|
|
.Fa size .
|
|
.El
|
|
.Sh RETURN VALUES
|
|
Upon successful completion a positive shared memory segment identifier
|
|
is returned.
|
|
Otherwise, -1 is returned and the global variable
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
.Bl -tag -width Er
|
|
.It Bq Er EACCES
|
|
A shared memory segment is already associated with
|
|
.Fa key
|
|
and the caller has no permission to access it.
|
|
.It Bq Er EEXIST
|
|
Both
|
|
.Dv IPC_CREAT
|
|
and
|
|
.Dv IPC_EXCL
|
|
are set in
|
|
.Fa shmflg ,
|
|
and a shared memory segment is already associated with
|
|
.Fa key .
|
|
.It Bq Er ENOSPC
|
|
A new shared memory identifier could not be created because the system limit
|
|
for the number of shared memory identifiers has been reached.
|
|
.It Bq Er ENOENT
|
|
.Dv IPC_CREAT
|
|
is not set in
|
|
.Fa shmflg
|
|
and no shared memory segment associated with
|
|
.Fa key
|
|
was found.
|
|
.It Bq Er ENOMEM
|
|
There is not enough memory left to create a shared memory segment of the
|
|
requested size.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr mmap 2 ,
|
|
.Xr shmat 2 ,
|
|
.Xr shmctl 2 ,
|
|
.Xr ftok 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Nm
|
|
system call conforms to
|
|
.St -xsh5 .
|
|
.Sh HISTORY
|
|
Shared memory segments appeared in the first release of
|
|
.At V .
|