1.\" $OpenBSD: shmget.2,v 1.9 2001/08/25 17:54:34 hugh Exp $ 2.\" $NetBSD: shmget.2,v 1.2 1997/03/27 08:20:39 mikel 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 SHMGET 2 35.Os 36.Sh NAME 37.Nm shmget 38.Nd get shared memory area identifier 39.Sh SYNOPSIS 40.Fd #include <sys/types.h> 41.Fd #include <sys/ipc.h> 42.Fd #include <sys/shm.h> 43.Ft int 44.Fn shmget "key_t key" "int size" "int shmflg" 45.Sh DESCRIPTION 46.Fn shmget 47returns the shared memory identifier associated with the key 48.Fa key . 49.Pp 50A shared memory segment is created if either 51.Fa key 52is equal to 53.Dv IPC_PRIVATE , 54or 55.Fa key 56does not have a shared memory segment identifier associated with it, and the 57.Dv IPC_CREAT 58bit is set in 59.Fa shmflg . 60.Pp 61If a new shared memory segment is created, the data structure associated with it (the 62.Va shmid_ds 63structure, see 64.Xr shmctl 2 ) 65is initialized as follows: 66.Bl -bullet 67.It 68.Va shm_perm.cuid 69and 70.Va shm_perm.uid 71are set to the effective uid of the calling process. 72.It 73.Va shm_perm.gid 74and 75.Va shm_perm.cgid 76are set to the effective gid of the calling process. 77.It 78.Va shm_perm.mode 79is set to the lower 9 bits of 80.Fa shmflg . 81.It 82.Va shm_lpid , 83.Va shm_nattch , 84.Va shm_atime , 85and 86.Va shm_dtime 87are set to 0 88.It 89.Va shm_ctime 90is set to the current time. 91.It 92.Va shm_segsz 93is set to the value of 94.Fa size . 95.El 96.Sh RETURN VALUES 97Upon successful completion a positive shared memory segment identifier is returned. 98Otherwise, \-1 is returned and the global variable 99.Va errno 100is set to indicate the error. 101.Sh ERRORS 102.Bl -tag -width Er 103.It Bq Er EACCES 104A shared memory segment is already associated with 105.Fa key 106and the caller has no permission to access it. 107.It Bq Er EEXIST 108Both 109.Dv IPC_CREAT 110and 111.Dv IPC_EXCL 112are set in 113.Fa shmflg , 114and a shared memory segment is already associated with 115.Fa key . 116.It Bq Er ENOSPC 117A new shared memory identifier could not be created because the system limit 118for the number of shared memory identifiers has been reached. 119.It Bq Er ENOENT 120.Dv IPC_CREAT 121was not set in 122.Fa shmflg 123and no shared memory segment associated with 124.Fa key 125was found. 126.It Bq Er ENOMEM 127There is not enough memory left to create a shared memory segment of the 128requested size. 129.El 130.Sh SEE ALSO 131.Xr mmap 2 , 132.Xr shmat 2 , 133.Xr shmctl 2 134