1.\" $NetBSD: sem_init.3,v 1.2 2012/03/08 21:59:29 joerg Exp $ 2.\" 3.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>. 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(s), this list of conditions and the following disclaimer as 11.\" the first lines of this file unmodified other than the possible 12.\" addition of one or more copyright notices. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice(s), this list of conditions and the following disclaimer in 15.\" the documentation and/or other materials provided with the 16.\" distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 19.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 22.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 25.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 26.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 27.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 28.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd February 29, 2012 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 librt 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 . 49A non-zero value for 50.Fa pshared 51specifies a shared semaphore that can be used by multiple processes, which this 52implementation is not capable of. 53.Pp 54Following a successful call to 55.Fn sem_init , 56.Fa sem 57can be used as an argument in subsequent calls to 58.Fn sem_wait , 59.Fn sem_timedwait , 60.Fn sem_trywait , 61.Fn sem_post , 62and 63.Fn sem_destroy . 64.Fa sem 65is no longer valid after a successful call to 66.Fa sem_destroy . 67.Sh RETURN VALUES 68.Rv -std sem_init 69.Sh ERRORS 70.Fn sem_init 71will fail if: 72.Bl -tag -width Er 73.It Bq Er EINVAL 74.Fa value 75exceeds SEM_VALUE_MAX. 76.It Bq Er ENOSPC 77Memory allocation error. 78.It Bq Er EPERM 79Unable to initialize a shared semaphore. 80.El 81.Sh SEE ALSO 82.Xr sem_destroy 3 , 83.Xr sem_post 3 , 84.Xr sem_timedwait 3 , 85.Xr sem_trywait 3 , 86.Xr sem_wait 3 87.Sh STANDARDS 88.Fn sem_init 89conforms to 90.St -p1003.1-96 . 91.Pp 92This implementation does not support shared semaphores, and reports this fact 93by setting 94.Va errno 95to 96.Er EPERM . 97This is perhaps a stretch of the intention of POSIX, but is 98compliant, with the caveat that 99.Fn sem_init 100always reports a permissions error when an attempt to create a shared semaphore 101is made. 102