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 February 15, 2000 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 . 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58.Xr sem_wait 3 , 59.Xr sem_trywait 3 , 60.Xr sem_post 3 , 61and 62.Xr sem_destroy 3 . 63The 64.Fa sem 65argument is no longer valid after a successful call to 66.Xr sem_destroy 3 . 67.Sh RETURN VALUES 68.Rv -std sem_init 69.Sh ERRORS 70The 71.Fn sem_init 72function will fail if: 73.Bl -tag -width Er 74.It Bq Er EINVAL 75The 76.Fa value 77argument exceeds 78.Dv SEM_VALUE_MAX . 79.It Bq Er ENOSPC 80Memory allocation error. 81.It Bq Er EPERM 82Unable to initialize a shared semaphore. 83.El 84.Sh SEE ALSO 85.Xr sem_destroy 3 , 86.Xr sem_getvalue 3 , 87.Xr sem_post 3 , 88.Xr sem_trywait 3 , 89.Xr sem_wait 3 , 90.Xr sem 4 91.Sh STANDARDS 92The 93.Fn sem_init 94function conforms to 95.St -p1003.1-96 . 96.Pp 97This implementation does not support shared semaphores, and reports this fact 98by setting 99.Va errno 100to 101.Er EPERM . 102This is perhaps a stretch of the intention of 103.Tn POSIX , 104but is 105compliant, with the caveat that 106.Fn sem_init 107always reports a permissions error when an attempt to create a shared semaphore 108is made. 109