1.\" $OpenBSD: semget.2,v 1.11 2000/10/18 05:12:11 aaron Exp $ 2.\" $NetBSD: semget.2,v 1.2 1997/03/27 08:20:41 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 SEMGET 2 35.Os 36.Sh NAME 37.Nm semget 38.Nd get semaphore set 39.Sh SYNOPSIS 40.Fd #include <sys/types.h> 41.Fd #include <sys/ipc.h> 42.Fd #include <sys/sem.h> 43.Ft int 44.Fn semget "key_t key" "int nsems" "int semflg" 45.Sh DESCRIPTION 46The 47.Fn semget 48system call returns the semaphore identifier associated with 49.Fa key . 50.Pp 51A new set containing 52.Fa nsems 53semaphores is created if either 54.Fa key 55is equal to 56.Dv IPC_PRIVATE , 57or 58.Fa key 59does not have a semaphore set associated with it and the 60.Dv IPC_CREAT 61bit is set in 62.Fa semflg . 63.Pp 64The access modes of the created semaphores is specified in 65.Fa semflg 66by 67.Tn OR Ns 'ing 68the following values: 69.Pp 70.Bd -literal -offset indent -compact 71SEM_A alter permission for owner 72SEM_R read permission for owner 73.Pp 74SEM_A >> 3 alter permission for group 75SEM_R >> 3 read permission for group 76.Pp 77SEM_A >> 6 alter permission for other 78SEM_R >> 6 read permission for other 79.Ed 80.Pp 81If a new set of semaphores is created, the data structure associated with it 82(the 83.Va semid_ds 84structure, see 85.Xr semctl 2 ) 86is intialized as follows: 87.Bl -bullet 88.It 89.Va sem_perm.cuid 90and 91.Va sem_perm.uid 92are set to the effective UID of the calling process. 93.It 94.Va sem_perm.gid 95and 96.Va sem_perm.cgid 97are set to the effective GID of the calling process. 98.It 99.Va sem_perm.mode 100is set to the lower 9 bits of 101.Fa semflg . 102.It 103.Va sem_nsems 104is set to the value of 105.Fa nsems 106.It 107.Va sem_ctime 108is set to the current time 109.It 110.Va sem_otime 111is set to 0 112.El 113.Sh RETURN VALUES 114.Fn semget 115returns a non-negative semaphore identifier if successful. 116Otherwise, \-1 is returned and 117.Va errno 118is set to reflect the error. 119.Sh ERRORS 120.Bl -tag -width Er 121.It Bq Er EACCES 122The caller has no permission to access a semaphore set already associated with 123.Fa key . 124.It Bq Er EEXIST 125Both 126.Dv IPC_CREAT 127and 128.Dv IPC_EXCL 129are set in 130.Fa semflg , 131and a semaphore set is already associated with 132.Fa key . 133.It Bq Er EINVAL 134.Va nsems 135is less than 0 or greater than the system limit for the number in a semaphore 136set. 137.Pp 138A semaphore set associated with 139.Fa key 140exists, but has fewer semaphores than the number specified in 141.Fa nsems . 142.It Bq Er ENOSPC 143A new set of semaphores could not be created because the system limit 144for the number of semaphores or the number of semaphore sets has been 145reached. 146.It Bq Er ENOENT 147.Dv IPC_CREAT 148was not set in 149.Fa semflg 150and no semaphore set associated with 151.Fa key 152was found. 153.El 154.Sh SEE ALSO 155.Xr semctl 2 , 156.Xr semop 2 157