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.Dd February 15, 2000 30.Dt SEM_INIT 3 31.Os 32.Sh NAME 33.Nm sem_init 34.Nd initialize an unnamed semaphore 35.Sh LIBRARY 36.Lb libc_r 37.Sh SYNOPSIS 38.In semaphore.h 39.Ft int 40.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value" 41.Sh DESCRIPTION 42The 43.Fn sem_init 44function initializes the unnamed semaphore pointed to by 45.Fa sem 46to have the value 47.Fa value . 48A non-zero value for 49.Fa pshared 50specifies a shared semaphore that can be used by multiple processes, which this 51implementation is not capable of. 52.Pp 53Following a successful call to 54.Fn sem_init , 55.Fa sem 56can be used as an argument in subsequent calls to 57.Xr sem_wait 3 , 58.Xr sem_trywait 3 , 59.Xr sem_post 3 , 60and 61.Xr sem_destroy 3 . 62The 63.Fa sem 64argument is no longer valid after a successful call to 65.Xr sem_destroy 3 . 66.Sh RETURN VALUES 67.Rv -std sem_init 68.Sh ERRORS 69The 70.Fn sem_init 71function will fail if: 72.Bl -tag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_trywait 3 , 85.Xr sem_wait 3 , 86.Xr sem 4 87.Sh STANDARDS 88The 89.Fn sem_init 90function conforms to 91.St -p1003.1-96 . 92.Pp 93This implementation does not support shared semaphores, and reports this fact 94by setting 95.Va errno 96to 97.Er EPERM . 98This is perhaps a stretch of the intention of POSIX, but is 99compliant, with the caveat that 100.Fn sem_init 101always reports a permissions error when an attempt to create a shared semaphore 102is made. 103