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: src/lib/libc_r/man/sem_init.3,v 1.1.2.9 2001/12/17 10:08:26 ru Exp $ 29.\" $DragonFly: src/lib/libc_r/man/sem_init.3,v 1.2 2003/06/17 04:26:48 dillon Exp $ 30.Dd April 15, 2009 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 libpthread 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in subsequent calls to 58.Fa sem_wait , 59.Fa sem_trywait , 60.Fa sem_post , 61and 62.Fa sem_destroy . 63.Fa sem 64is no longer valid after a successful call to 65.Fa sem_destroy . 66.Sh RETURN VALUES 67.Rv -std sem_init 68.Sh ERRORS 69.Fn sem_init 70will fail if: 71.Bl -tag -width Er 72.It Bq Er EINVAL 73.Fa value 74exceeds SEM_VALUE_MAX. 75.It Bq Er ENOSPC 76Memory allocation error. 77.It Bq Er EPERM 78Unable to initialize a shared semaphore. 79.El 80.Sh SEE ALSO 81.Xr sem_destroy 3 , 82.Xr sem_post 3 , 83.Xr sem_trywait 3 , 84.Xr sem_wait 3 85.Sh STANDARDS 86.Fn sem_init 87conforms to 88.St -p1003.1-96 . 89.Pp 90This implementation does not support shared semaphores, and reports this fact 91by setting 92.Va errno 93to 94.Er EPERM . 95This is perhaps a stretch of the intention of POSIX, but is 96compliant, with the caveat that 97.Fn sem_init 98always reports a permissions error when an attempt to create a shared semaphore 99is made. 100