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 February 29, 2012 .Dt SEM_INIT 3 .Os .Sh NAME .Nm sem_init .Nd initialize an unnamed semaphore .Sh LIBRARY .Lb librt .Sh SYNOPSIS n 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 . A non-zero value for .Fa pshared specifies a shared semaphore that can be used by multiple processes, which this implementation is not capable of.
p Following a successful call to .Fn sem_init , .Fa sem can be used as an argument in subsequent calls to .Fn sem_wait , .Fn sem_timedwait , .Fn sem_trywait , .Fn sem_post , and .Fn sem_destroy . .Fa sem is no longer valid after a successful call to .Fa sem_destroy . .Sh RETURN VALUES .Rv -std sem_init .Sh ERRORS .Fn sem_init will fail if: l -tag -width Er t Bq Er EINVAL .Fa value exceeds SEM_VALUE_MAX. t Bq Er ENOSPC Memory allocation error. t Bq Er EPERM Unable to initialize a shared semaphore. .El .Sh SEE ALSO .Xr sem_destroy 3 , .Xr sem_post 3 , .Xr sem_timedwait 3 , .Xr sem_trywait 3 , .Xr sem_wait 3 .Sh STANDARDS .Fn sem_init conforms to .St -p1003.1-96 .
p This implementation does not support shared semaphores, and reports this fact by setting .Va errno to .Er EPERM . This is perhaps a stretch of the intention of POSIX, but is compliant, with the caveat that .Fn sem_init always reports a permissions error when an attempt to create a shared semaphore is made.