1.\" 2.\" Copyright (c) 1995 David Hovemeyer <daveho@infocom.com> 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/lib/libc/sys/shmat.2,v 1.8.2.6 2001/12/14 18:34:01 ru Exp $ 27.\" $DragonFly: src/lib/libc/sys/shmat.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 28.\" 29.Dd August 2, 1995 30.Dt SHMAT 2 31.Os 32.Sh NAME 33.Nm shmat , 34.Nm shmdt 35.Nd attach or detach shared memory 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In machine/param.h 40.In sys/types.h 41.In sys/ipc.h 42.In sys/shm.h 43.Ft void * 44.Fn shmat "int shmid" "void *addr" "int flag" 45.Ft int 46.Fn shmdt "void *addr" 47.Sh DESCRIPTION 48.Fn Shmat 49attaches the shared memory segment identified by 50.Fa shmid 51to the calling process's address space. The address where the segment 52is attached is determined as follows: 53.\" 54.\" These are cribbed almost exactly from Stevens, _Advanced Programming in 55.\" the UNIX Environment_. 56.\" 57.Bl -bullet 58.It 59If 60.Fa addr 61is 0, the segment is attached at an address selected by the 62kernel. 63.It 64If 65.Fa addr 66is nonzero and SHM_RND is not specified in 67.Fa flag , 68the segment is attached the specified address. 69.It 70If 71.Fa addr 72is specified and SHM_RND is specified, 73.Fa addr 74is rounded down to the nearest multiple of SHMLBA. 75.El 76.Pp 77.Fn Shmdt 78detaches the shared memory segment at the address specified by 79.Fa addr 80from the calling process's address space. 81.Sh RETURN VALUES 82Upon success, 83.Fn shmat 84returns the address where the segment is attached; otherwise, -1 85is returned and 86.Va errno 87is set to indicate the error. 88.Pp 89.Rv -std shmdt 90.Sh ERRORS 91.Fn Shmat 92will fail if: 93.Bl -tag -width Er 94.It Bq Er EINVAL 95No shared memory segment was found corresponding to 96.Fa shmid . 97.It Bq Er EINVAL 98.Fa addr 99was not an acceptable address. 100.El 101.Pp 102.Fn Shmdt 103will fail if: 104.Bl -tag -width Er 105.It Bq Er EINVAL 106.Fa addr 107does not point to a shared memory segment. 108.El 109.Sh "SEE ALSO" 110.Xr shmctl 2 , 111.Xr shmget 2 112