.\" $Darwin$ .\" .\" 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 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 semctl 2 , .Xr semget 2 , .Xr semop 2 , .Xr sem_open 2 , .Xr sem_trywait 2 , .Xr sem_wait 2 .Sh HISTORY .Fn sem_post is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).