1.\" Copyright (C) 2000 Jason Evans <jasone@canonware.com>. 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_POST 3 31.Os 32.Sh NAME 33.Nm sem_post 34.Nd increment (unlock) a semaphore 35.Sh SYNOPSIS 36.Fd #include <semaphore.h> 37.Ft int 38.Fn sem_post "sem_t *sem" 39.Sh DESCRIPTION 40The 41.Fn sem_post 42function increments (unlocks) the semaphore pointed to by 43.Fa sem . 44If there are threads blocked on the semaphore when 45.Fn sem_post 46is called, then the highest priority thread that has been blocked the longest on 47the semaphore will be allowed to return from 48.Fn sem_wait . 49.Sh RETURN VALUES 50If successful, 51.Fn sem_post 52returns 0. Otherwise, -1 is returned and 53.Va errno 54is set to indicate the type of 55error. 56.Sh ERRORS 57.Fn sem_post 58will fail if: 59.Bl -tag -width Er 60.It Bq Er EINVAL 61.Fa sem 62points to an invalid semaphore. 63.El 64.Sh SEE ALSO 65.Xr sem_wait 3 , 66.Xr sem_trywait 3 67.Sh STANDARDS 68.Fn sem_post 69conforms to ISO/IEC 9945-1 ANSI/IEEE 70.Pq Dq Tn POSIX 71Std 1003.1 1996 Edition. 72