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.Dd February 15, 2000 29.Dt SEM_GETVALUE 3 30.Os 31.Sh NAME 32.Nm sem_getvalue 33.Nd get the value of a semaphore 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In semaphore.h 38.Ft int 39.Fn sem_getvalue "sem_t * restrict sem" "int * restrict sval" 40.Sh DESCRIPTION 41The 42.Fn sem_getvalue 43function sets the variable pointed to by 44.Fa sval 45to the current value of the semaphore pointed to by 46.Fa sem , 47as of the time that the call to 48.Fn sem_getvalue 49is actually run. 50.Sh RETURN VALUES 51.Rv -std sem_getvalue 52.Sh ERRORS 53The 54.Fn sem_getvalue 55function will fail if: 56.Bl -tag -width Er 57.It Bq Er EINVAL 58The 59.Fa sem 60argument 61points to an invalid semaphore. 62.El 63.Sh SEE ALSO 64.Xr sem_post 3 , 65.Xr sem_trywait 3 , 66.Xr sem_wait 3 67.Sh STANDARDS 68The 69.Fn sem_getvalue 70function conforms to 71.St -p1003.1-96 . 72.Pp 73The value of the semaphore is never negative, even if there are threads blocked 74on the semaphore. 75.Tn POSIX 76is somewhat ambiguous in its wording with regard to 77what the value of the semaphore should be if there are blocked waiting threads, 78but this behavior is conformant, given the wording of the specification. 79