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.Fd #include <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in subsequent calls to 57.Fa sem_wait , 58.Fa sem_trywait , 59.Fa sem_post , 60and 61.Fa sem_destroy . 62.Fa sem 63is no longer valid after a successful call to 64.Fa sem_destroy . 65.Sh RETURN VALUES 66If successful, 67.Fn sem_init 68returns 0. Otherwise, -1 is returned and 69.Va errno 70is set to indicate the type of 71error. 72.Sh ERRORS 73.Fn sem_init 74will fail if: 75.Bl -tag -width Er 76.It Bq Er EINVAL 77.Fa value 78exceeds 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_post 3 , 87.Xr sem_trywait 3 , 88.Xr sem_wait 3 89.Sh STANDARDS 90.Fn sem_init 91conforms to 92.St -p1003.1-96 . 93.Pp 94This implementation does not support shared semaphores, and reports this fact 95by setting 96.Va errno 97to 98.Er EPERM . 99This is perhaps a stretch of the intention of POSIX, but is 100compliant, with the caveat that 101.Fn sem_init 102always reports a permissions error when an attempt to create a shared semaphore 103is made. 104