1b0a1b4f8SJason Evans.\" Copyright (C) 2000 Jason Evans <jasone@canonware.com>. 2b0a1b4f8SJason Evans.\" All rights reserved. 3b0a1b4f8SJason Evans.\" 4b0a1b4f8SJason Evans.\" Redistribution and use in source and binary forms, with or without 5b0a1b4f8SJason Evans.\" modification, are permitted provided that the following conditions 6b0a1b4f8SJason Evans.\" are met: 7b0a1b4f8SJason Evans.\" 1. Redistributions of source code must retain the above copyright 8b0a1b4f8SJason Evans.\" notice(s), this list of conditions and the following disclaimer as 9b0a1b4f8SJason Evans.\" the first lines of this file unmodified other than the possible 10b0a1b4f8SJason Evans.\" addition of one or more copyright notices. 11b0a1b4f8SJason Evans.\" 2. Redistributions in binary form must reproduce the above copyright 12b0a1b4f8SJason Evans.\" notice(s), this list of conditions and the following disclaimer in 13b0a1b4f8SJason Evans.\" the documentation and/or other materials provided with the 14b0a1b4f8SJason Evans.\" distribution. 15b0a1b4f8SJason Evans.\" 16b0a1b4f8SJason Evans.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17b0a1b4f8SJason Evans.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18b0a1b4f8SJason Evans.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19b0a1b4f8SJason Evans.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 20b0a1b4f8SJason Evans.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21b0a1b4f8SJason Evans.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22b0a1b4f8SJason Evans.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 23b0a1b4f8SJason Evans.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 24b0a1b4f8SJason Evans.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 25b0a1b4f8SJason Evans.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 26b0a1b4f8SJason Evans.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27b0a1b4f8SJason Evans.\" 28b0a1b4f8SJason Evans.\" $FreeBSD$ 29b0a1b4f8SJason Evans.Dd February 15, 2000 30b0a1b4f8SJason Evans.Dt SEM_GETVALUE 3 31b0a1b4f8SJason Evans.Os 32b0a1b4f8SJason Evans.Sh NAME 33b0a1b4f8SJason Evans.Nm sem_getvalue 34b0a1b4f8SJason Evans.Nd get the value of a semaphore 35d8a78688SAlexey Zelkin.Sh LIBRARY 36d8a78688SAlexey Zelkin.Lb libc_r 37b0a1b4f8SJason Evans.Sh SYNOPSIS 38b0a1b4f8SJason Evans.Fd #include <semaphore.h> 39b0a1b4f8SJason Evans.Ft int 40b0a1b4f8SJason Evans.Fn sem_getvalue "sem_t *sem" "int *sval" 41b0a1b4f8SJason Evans.Sh DESCRIPTION 42b0a1b4f8SJason EvansThe 43b0a1b4f8SJason Evans.Fn sem_getvalue 44b0a1b4f8SJason Evansfunction sets the variable pointed to by 45b0a1b4f8SJason Evans.Fa sval 46b0a1b4f8SJason Evansto the current value of the semaphore pointed to by 47b0a1b4f8SJason Evans.Fa sem , 48b0a1b4f8SJason Evansas of the time that the call to 49b0a1b4f8SJason Evans.Fn sem_getvalue 50b0a1b4f8SJason Evansis actually run. 51b0a1b4f8SJason Evans.Sh RETURN VALUES 52b0a1b4f8SJason EvansIf successful, 53b0a1b4f8SJason Evans.Fn sem_getvalue 54b0a1b4f8SJason Evansreturns 0. Otherwise, -1 is returned and 55b0a1b4f8SJason Evans.Va errno 56b0a1b4f8SJason Evansis set to indicate the type of 57b0a1b4f8SJason Evanserror. 58b0a1b4f8SJason Evans.Sh ERRORS 59b0a1b4f8SJason Evans.Fn sem_getvalue 60b0a1b4f8SJason Evanswill fail if: 61b0a1b4f8SJason Evans.Bl -tag -width Er 62b0a1b4f8SJason Evans.It Bq Er EINVAL 63b0a1b4f8SJason Evans.Fa sem 64b0a1b4f8SJason Evanspoints to an invalid semaphore. 65b0a1b4f8SJason Evans.El 66b0a1b4f8SJason Evans.Sh SEE ALSO 67b0a1b4f8SJason Evans.Xr sem_post 3 , 6882db3da3SJason Evans.Xr sem_trywait 3 , 6982db3da3SJason Evans.Xr sem_wait 3 70b0a1b4f8SJason Evans.Sh STANDARDS 71b0a1b4f8SJason Evans.Fn sem_getvalue 72b0a1b4f8SJason Evansconforms to ISO/IEC 9945-1 ANSI/IEEE 73b0a1b4f8SJason Evans.Pq Dq Tn POSIX 74b0a1b4f8SJason EvansStd 1003.1 1996 Edition. 75b0a1b4f8SJason Evans.Pp 76b0a1b4f8SJason EvansThe value of the semaphore is never negative, even if there are threads blocked 77b0a1b4f8SJason Evanson the semaphore. POSIX is somewhat ambiguous in its wording with regard to 78b0a1b4f8SJason Evanswhat the value of the semaphore should be if there are blocked waiting threads, 79b0a1b4f8SJason Evansbut this behavior is conformant, given the wording of the specification. 80