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. 51The address where the segment is 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 66.Dv SHM_RND 67is not specified in 68.Fa flag , 69the segment is attached the specified address. 70.It 71If 72.Fa addr 73is specified and 74.Dv SHM_RND 75is specified, 76.Fa addr 77is rounded down to the nearest multiple of 78.Dv SHMLBA . 79.El 80.Pp 81.Fn Shmdt 82detaches the shared memory segment at the address specified by 83.Fa addr 84from the calling process's address space. 85.Sh RETURN VALUES 86Upon success, 87.Fn shmat 88returns the address where the segment is attached; otherwise, -1 89is returned and 90.Va errno 91is set to indicate the error. 92.Pp 93.Rv -std shmdt 94.Sh ENVIRONMENT 95The XSI Interprocess Communication family of functions is also available 96as an implementation in userspace. 97To use it, the 98.Xr sysvipcd 8 99daemon has to be running. 100.Pp 101If the 102.Ev USR_SYSVIPC 103variable is set in a process' environment, the process and its children 104will use the userspace implementation. 105.Sh ERRORS 106.Fn Shmat 107will fail if: 108.Bl -tag -width Er 109.It Bq Er EINVAL 110No shared memory segment was found corresponding to 111.Fa shmid . 112.It Bq Er EINVAL 113.Fa addr 114was not an acceptable address. 115.El 116.Pp 117.Fn Shmdt 118will fail if: 119.Bl -tag -width Er 120.It Bq Er EINVAL 121.Fa addr 122does not point to a shared memory segment. 123.El 124.Sh "SEE ALSO" 125.Xr shmctl 2 , 126.Xr shmget 2 127.Sh AUTHORS 128.An -nosplit 129The 130.Dx 131specific userspace implementation (see 132.Sx ENVIRONMENT ) 133was written by 134.An Larisa Grigore . 135