xnu-1699.22.73.tar.gz

[apple/xnu.git] / bsd / man / man2 / sem_post.2

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+.\"    $Darwin$
+.\"
+.\" Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
+.\"
+.\" @APPLE_LICENSE_HEADER_START@
+.\" 
+.\" The contents of this file constitute Original Code as defined in and
+.\" are subject to the Apple Public Source License Version 1.1 (the
+.\" "License").  You may not use this file except in compliance with the
+.\" License.  Please obtain a copy of the License at
+.\" http://www.apple.com/publicsource and read it before using this file.
+.\" 
+.\" This Original Code and all software distributed under the License are
+.\" distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+.\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+.\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+.\" FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
+.\" License for the specific language governing rights and limitations
+.\" under the License.
+.\" 
+.\" @APPLE_LICENSE_HEADER_END@
+.\"
+.Dd June 8, 2000
+.Dt SEM_POST 2
+.Os Darwin
+.Sh NAME
+.Nm sem_post
+.Nd unlock a semaphore
+.Sh SYNOPSIS
+.Fd #include <semaphore.h>
+.Ft int
+.Fn sem_post "sem_t *sem"
+.Sh DESCRIPTION
+The semaphore referenced by
+.Fa sem
+is unlocked, the value of the semaphore is incremented, and all
+threads which are waiting on the semaphore are awakened.
+.Pp
+.Fn sem_post
+is reentrant with respect to signals and may be called from within a
+signal hanlder.
+.Pp
+If successful,
+.Fn sem_post
+will return 0.  Otherwise, -1 is returned and
+.Va errno
+is set.
+.Sh ERRORS
+.Fn sem_post
+succeeds unless:
+.Bl -tag -width Er
+.It Bq Er EINVAL
+.Fa sem
+is not a valid semaphore descriptor.
+.El
+.Sh SEE ALSO
+.Xr sem_open 2 ,
+.Xr sem_trywait 2 ,
+.Xr sem_wait 2 ,
+.Xr semctl 2 ,
+.Xr semget 2 ,
+.Xr semop 2
+.Sh HISTORY
+.Fn sem_post
+is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).