| | 1 | .\" $OpenBSD: shmat.2,v 1.2 1996/10/08 01:20:15 michaels Exp $ |
| | 2 | .\" $NetBSD: shmat.2,v 1.1 1995/10/16 23:49:29 jtc Exp $ |
| | 3 | .\" |
| | 4 | .\" Copyright (c) 1995 Frank van der Linden |
| | 5 | .\" All rights reserved. |
| | 6 | .\" |
| | 7 | .\" Redistribution and use in source and binary forms, with or without |
| | 8 | .\" modification, are permitted provided that the following conditions |
| | 9 | .\" are met: |
| | 10 | .\" 1. Redistributions of source code must retain the above copyright |
| | 11 | .\" notice, this list of conditions and the following disclaimer. |
| | 12 | .\" 2. Redistributions in binary form must reproduce the above copyright |
| | 13 | .\" notice, this list of conditions and the following disclaimer in the |
| | 14 | .\" documentation and/or other materials provided with the distribution. |
| | 15 | .\" 3. All advertising materials mentioning features or use of this software |
| | 16 | .\" must display the following acknowledgement: |
| | 17 | .\" This product includes software developed for the NetBSD Project |
| | 18 | .\" by Frank van der Linden |
| | 19 | .\" 4. The name of the author may not be used to endorse or promote products |
| | 20 | .\" derived from this software without specific prior written permission |
| | 21 | .\" |
| | 22 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| | 23 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| | 24 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| | 25 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| | 26 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| | 27 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| | 28 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| | 29 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| | 30 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| | 31 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| | 32 | .\"/ |
| | 33 | .Dd August 17, 1995 |
| | 34 | .Dt SHMAT 2 |
| | 35 | .Os |
| | 36 | .Sh NAME |
| | 37 | .Nm shmat , |
| | 38 | .Nm shmdt |
| | 39 | .Nd map/unmap shared memory |
| | 40 | .Sh SYNOPSIS |
| | 41 | .Fd #include <sys/types.h> |
| | 42 | .Fd #include <sys/ipc.h> |
| | 43 | .Fd #include <sys/shm.h> |
| | 44 | .Ft void * |
| | 45 | .Fn shmat "int shmid" "void *shmaddr" "int shmflg" |
| | 46 | .Ft int |
| | 47 | .Fn shmdt "void *shmaddr" |
| | 48 | .Sh DESCRIPTION |
| | 49 | .Fn shmat |
| | 50 | maps the shared memory segment associated with the shared memory identifier |
| | 51 | .Fa shmid |
| | 52 | into the address space of the calling process. The address at which the |
| | 53 | segment is mapped is determined by the |
| | 54 | .Fa shmaddr |
| | 55 | parameter. If it is equal to 0, the system will pick an address itself. |
| | 56 | Otherwise, an attempt is made to map the shared memory segment at the |
| | 57 | address |
| | 58 | .Fa shmaddr |
| | 59 | specifies. If SHM_RND is set in |
| | 60 | .Fa shmflg , |
| | 61 | the system will round the address down to a multiple of SHMLBA bytes |
| | 62 | (SHMLBA is defined in |
| | 63 | .Aq Pa sys/shm.h |
| | 64 | ). |
| | 65 | |
| | 66 | A shared memory segment can be mapped read-only by specifying the |
| | 67 | SHM_RDONLY flag in |
| | 68 | .Fa shmflg . |
| | 69 | |
| | 70 | .Fn shmdt |
| | 71 | unmaps the shared memory segment that is currently mapped at |
| | 72 | .Fa shmaddr |
| | 73 | from the calling process' address space. |
| | 74 | .Fa shmaddr |
| | 75 | must be a value returned by a prior |
| | 76 | .Fn shmat |
| | 77 | call. A shared memory segment will remain existant until it is removed by |
| | 78 | a call to |
| | 79 | .Xr shmctl 2 |
| | 80 | with the IPC_RMID command. |
| | 81 | .Sh RETURN VALUES |
| | 82 | .Fn shmat |
| | 83 | returns the address at which the shared memory segment has been mapped into |
| | 84 | the calling process' address space when successful, |
| | 85 | .Fn shmdt |
| | 86 | returns 0 on successful completion. Otherwise, a value of -1 is returned, |
| | 87 | and the global variable |
| | 88 | .Va errno |
| | 89 | is set to indicate the error. |
| | 90 | .Sh ERRORS |
| | 91 | .Fn shmat |
| | 92 | will fail if: |
| | 93 | .Bl -tag -width Er |
| | 94 | .It Bq Er EACCESS |
| | 95 | The calling process has no permission to access this shared memory segment. |
| | 96 | .It Bq Er ENOMEM |
| | 97 | There is not enough available data space for the calling process to |
| | 98 | map the shared memory segment. |
| | 99 | .It Bq Er EINVAL |
| | 100 | .Fa shmid |
| | 101 | is not a valid shared memory identifier. |
| | 102 | |
| | 103 | .Fa shmaddr |
| | 104 | specifies an illegal address. |
| | 105 | .It Bq Er EMFILE |
| | 106 | The number of shared memory segments has reached the system-wide limit. |
| | 107 | .El |
| | 108 | |
| | 109 | .Fn shmdt |
| | 110 | will fail if: |
| | 111 | .Bl -tag -width Er |
| | 112 | .It Bq Er EINVAL |
| | 113 | .Fa shmaddr |
| | 114 | is not the start address of a mapped shared memory segment. |
| | 115 | .Sh SEE ALSO |
| | 116 | .Xr shmctl 2 , |
| | 117 | .Xr shmget 2 , |
| | 118 | .Xr mmap 2 |
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