.\" .\" Copyright (c) 1995 David Hovemeyer .\" .\" 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. .\" .\" $FreeBSD$ .\" .Dd August 2, 1995 .Dt SHMAT 2 .Os .Sh NAME .Nm shmat , .Nm shmdt .Nd attach or detach shared memory .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include .Fd #include .Fd #include .Fd #include .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 identified 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 specified 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 .Rv -std shmdt .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. .El .Sh "SEE ALSO" .Xr shmctl 2 , .Xr shmget 2