1.\" Copyright (C) 2000 Jason Evans <jasone@canonware.com>. 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 SYNOPSIS 36.Fd #include <semaphore.h> 37.Ft int 38.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value" 39.Sh DESCRIPTION 40The 41.Fn sem_init 42function initializes the unnamed semaphore pointed to by 43.Fa sem 44to have the value 45.Fa value . 46A non-zero value for 47.Fa pshared 48specifies a shared semaphore that can be used by multiple processes, which this 49implementation is not capable of. 50.Pp 51Following a successful call to 52.Fn sem_init , 53.Fa sem 54can be used as an argument in subsequent calls to 55.Fa sem_wait , 56.Fa sem_trywait , 57.Fa sem_post , 58and 59.Fa sem_destroy . 60.Fa sem 61is no longer valid after a successful call to 62.Fa sem_destroy . 63.Sh RETURN VALUES 64If successful, 65.Fn sem_init 66returns 0. Otherwise, -1 is returned and 67.Va errno 68is set to indicate the type of 69error. 70.Sh ERRORS 71.Fn sem_init 72will fail if: 73.Bl -tag -width Er 74.It Bq Er EINVAL 75.Fa value 76exceeds SEM_VALUE_MAX. 77.It Bq Er ENOSPC 78Memory allocation error. 79.It Bq Er EPERM 80Unable to initialize a shared semaphore. 81.El 82.Sh SEE ALSO 83.Xr sem_wait 3 , 84.Xr sem_trywait 3 , 85.Xr sem_post 3 , 86.Xr sem_destroy 87.Sh STANDARDS 88.Fn sem_init 89conforms to ISO/IEC 9945-1 ANSI/IEEE 90.Pq Dq Tn POSIX 91Std 1003.1 1996 Edition. 92.Pp 93This implementation does not support shared semaphores, and reports this fact 94by setting 95.Va errno 96to EPERM. This is perhaps a stretch of the intention of POSIX, but is 97compliant, with the caveat that 98.Fn sem_init 99always reports a permissions error when an attempt to create a shared semaphore 100is made. 101