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Diffstat (limited to 'lib/libc/sys/shmget.2')
-rw-r--r-- | lib/libc/sys/shmget.2 | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/lib/libc/sys/shmget.2 b/lib/libc/sys/shmget.2 new file mode 100644 index 0000000..3df3272 --- /dev/null +++ b/lib/libc/sys/shmget.2 @@ -0,0 +1,138 @@ +.\" +.\" 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 |