.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice(s), this list of conditions and the following disclaimer as
.\"    the first lines of this file unmodified other than the possible
.\"    addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice(s), this list of conditions and the following disclaimer in
.\"    the documentation and/or other materials provided with the
.\"    distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd January 9, 2010
.Dt SEM_INIT 3
.Os
.Sh NAME
.Nm sem_init
.Nd initialize an unnamed semaphore
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In semaphore.h
.Ft int
.Fn sem_init "sem_t *sem" "int pshared" "unsigned int value"
.Sh DESCRIPTION
The
.Fn sem_init
function initializes the unnamed semaphore pointed to by
.Fa sem
to have the value
.Fa value .
.Pp
A non-zero value for
.Fa pshared
specifies a shared semaphore that can be used by multiple processes,
the semaphore should be located in shared memory region (see
.Xr mmap 2 ,
.Xr shm_open 2 ,
and
.Xr shmget 2 ) ,
any process having read and write access to address
.Fa sem
can perform semaphore operations on
.Fa sem .
.Pp
Following a successful call to
.Fn sem_init ,
.Fa sem
can be used as an argument in subsequent calls to
.Xr sem_wait 3 ,
.Xr sem_trywait 3 ,
.Xr sem_post 3 ,
and
.Xr sem_destroy 3 .
The
.Fa sem
argument is no longer valid after a successful call to
.Xr sem_destroy 3 .
.Sh RETURN VALUES
.Rv -std sem_init
.Sh ERRORS
The
.Fn sem_init
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa value
argument exceeds
.Dv SEM_VALUE_MAX .
.It Bq Er ENOSPC
Memory allocation error.
.El
.Sh SEE ALSO
.Xr sem_destroy 3 ,
.Xr sem_getvalue 3 ,
.Xr sem_post 3 ,
.Xr sem_trywait 3 ,
.Xr sem_wait 3
.Sh STANDARDS
The
.Fn sem_init
function conforms to
.St -p1003.1-96 .