1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>. 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: src/lib/libc_r/man/sem_getvalue.3,v 1.1.2.7 2001/12/17 10:08:26 ru Exp $ 29.\" $DragonFly: src/lib/libc_r/man/sem_getvalue.3,v 1.2 2003/06/17 04:26:48 dillon Exp $ 30.Dd April 15, 2009 31.Dt SEM_GETVALUE 3 32.Os 33.Sh NAME 34.Nm sem_getvalue 35.Nd get the value of a semaphore 36.Sh LIBRARY 37.Lb libpthread 38.Sh SYNOPSIS 39.In semaphore.h 40.Ft int 41.Fn sem_getvalue "sem_t *sem" "int *sval" 42.Sh DESCRIPTION 43The 44.Fn sem_getvalue 45function sets the variable pointed to by 46.Fa sval 47to the current value of the semaphore pointed to by 48.Fa sem , 49as of the time that the call to 50.Fn sem_getvalue 51is actually run. 52.Sh RETURN VALUES 53.Rv -std sem_getvalue 54.Sh ERRORS 55.Fn sem_getvalue 56will fail if: 57.Bl -tag -width Er 58.It Bq Er EINVAL 59.Fa sem 60points to an invalid semaphore. 61.El 62.Sh SEE ALSO 63.Xr sem_post 3 , 64.Xr sem_trywait 3 , 65.Xr sem_wait 3 66.Sh STANDARDS 67.Fn sem_getvalue 68conforms to 69.St -p1003.1-96 . 70.Pp 71The value of the semaphore is never negative, even if there are threads blocked 72on the semaphore. POSIX is somewhat ambiguous in its wording with regard to 73what the value of the semaphore should be if there are blocked waiting threads, 74but this behavior is conformant, given the wording of the specification. 75