1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as 9.\" the first lines of this file unmodified other than the possible 10.\" addition of one or more copyright notices. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice(s), this list of conditions and the following disclaimer in 13.\" the documentation and/or other materials provided with the 14.\" distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 20.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 23.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 24.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 25.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 26.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27.\" 28.\" $FreeBSD$ 29.\" 30.Dd January 9, 2010 31.Dt SEM_INIT 3 32.Os 33.Sh NAME 34.Nm sem_init 35.Nd initialize an unnamed semaphore 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In semaphore.h 40.Ft int 41.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value" 42.Sh DESCRIPTION 43The 44.Fn sem_init 45function initializes the unnamed semaphore pointed to by 46.Fa sem 47to have the value 48.Fa value . 49.Pp 50A non-zero value for 51.Fa pshared 52specifies a shared semaphore that can be used by multiple processes, 53the semaphore should be located in shared memory region (see 54.Xr mmap 2 , 55.Xr shm_open 2 , 56and 57.Xr shmget 2 ) , 58any process having read and write access to address 59.Fa sem 60can perform semaphore operations on 61.Fa sem . 62.Pp 63Following a successful call to 64.Fn sem_init , 65.Fa sem 66can be used as an argument in subsequent calls to 67.Xr sem_wait 3 , 68.Xr sem_trywait 3 , 69.Xr sem_post 3 , 70and 71.Xr sem_destroy 3 . 72The 73.Fa sem 74argument is no longer valid after a successful call to 75.Xr sem_destroy 3 . 76.Sh RETURN VALUES 77.Rv -std sem_init 78.Sh ERRORS 79The 80.Fn sem_init 81function will fail if: 82.Bl -tag -width Er 83.It Bq Er EINVAL 84The 85.Fa value 86argument exceeds 87.Dv SEM_VALUE_MAX . 88.It Bq Er ENOSPC 89Memory allocation error. 90.El 91.Sh SEE ALSO 92.Xr sem_destroy 3 , 93.Xr sem_getvalue 3 , 94.Xr sem_post 3 , 95.Xr sem_trywait 3 , 96.Xr sem_wait 3 97.Sh STANDARDS 98The 99.Fn sem_init 100function conforms to 101.St -p1003.1-96 . 102