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