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.\" 28.Dd January 4, 2014 29.Dt SHMAT 2 30.Os 31.Sh NAME 32.Nm shmat , 33.Nm shmdt 34.Nd attach or detach shared memory 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In machine/param.h 39.In sys/types.h 40.In sys/ipc.h 41.In sys/shm.h 42.Ft void * 43.Fn shmat "int shmid" "const void *addr" "int flag" 44.Ft int 45.Fn shmdt "const void *addr" 46.Sh DESCRIPTION 47.Fn Shmat 48attaches the shared memory segment identified by 49.Fa shmid 50to the calling process's address space. The address where the segment 51is attached is determined as follows: 52.\" 53.\" These are cribbed almost exactly from Stevens, _Advanced Programming in 54.\" the UNIX Environment_. 55.\" 56.Bl -bullet 57.It 58If 59.Fa addr 60is 0, the segment is attached at an address selected by the 61kernel. 62.It 63If 64.Fa addr 65is nonzero and SHM_RND is not specified in 66.Fa flag , 67the segment is attached the specified address. 68.It 69If 70.Fa addr 71is specified and SHM_RND is specified, 72.Fa addr 73is rounded down to the nearest multiple of SHMLBA. 74.El 75.Pp 76.Fn Shmdt 77detaches the shared memory segment at the address specified by 78.Fa addr 79from the calling process's address space. 80.Sh RETURN VALUES 81Upon success, 82.Fn shmat 83returns the address where the segment is attached; otherwise, -1 84is returned and 85.Va errno 86is set to indicate the error. 87.Pp 88.Rv -std shmdt 89.Sh ENVIRONMENT 90The XSI Interprocess Communication family of functions is also available 91as an implementation in userspace. 92To use it, the 93.Xr sysvipcd 8 94daemon has to be running. 95.Pp 96If the 97.Ev USR_SYSVIPC 98variable is set in a process' environment, the process and its children 99will use the userspace implementation. 100.Sh ERRORS 101.Fn Shmat 102will fail if: 103.Bl -tag -width Er 104.It Bq Er EINVAL 105No shared memory segment was found corresponding to 106.Fa shmid . 107.It Bq Er EINVAL 108.Fa addr 109was not an acceptable address. 110.El 111.Pp 112.Fn Shmdt 113will fail if: 114.Bl -tag -width Er 115.It Bq Er EINVAL 116.Fa addr 117does not point to a shared memory segment. 118.El 119.Sh "SEE ALSO" 120.Xr shmctl 2 , 121.Xr shmget 2 122.Sh AUTHORS 123.An -nosplit 124The 125.Dx 126specific userspace implementation (see 127.Sx ENVIRONMENT ) 128was written by 129.An Larisa Grigore . 130