Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
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.Dd February 15, 2000 .Dt SEM_GETVALUE 3 .Os .Sh NAME .Nm sem_getvalue .Nd get the value of a semaphore .Sh LIBRARY .Lb libc .Sh SYNOPSIS n semaphore.h .Ft int .Fn sem_getvalue "sem_t * restrict sem" "int * restrict sval" .Sh DESCRIPTION The .Fn sem_getvalue function sets the variable pointed to by .Fa sval to the current value of the semaphore pointed to by .Fa sem , as of the time that the call to .Fn sem_getvalue is actually run. .Sh RETURN VALUES .Rv -std sem_getvalue .Sh ERRORS The .Fn sem_getvalue function will fail if: l -tag -width Er t Bq Er EINVAL The .Fa sem argument points to an invalid semaphore. .El .Sh SEE ALSO .Xr sem_post 3 , .Xr sem_trywait 3 , .Xr sem_wait 3 .Sh STANDARDS The .Fn sem_getvalue function conforms to .St -p1003.1-96 .
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice(s), this list of conditions and the following disclaimer as
the first lines of this file unmodified other than the possible
addition of one or more copyright notices.
2. Redistributions in binary form must reproduce the above copyright
notice(s), this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
$FreeBSD$
.Dd February 15, 2000 .Dt SEM_GETVALUE 3 .Os .Sh NAME .Nm sem_getvalue .Nd get the value of a semaphore .Sh LIBRARY .Lb libc .Sh SYNOPSIS n semaphore.h .Ft int .Fn sem_getvalue "sem_t * restrict sem" "int * restrict sval" .Sh DESCRIPTION The .Fn sem_getvalue function sets the variable pointed to by .Fa sval to the current value of the semaphore pointed to by .Fa sem , as of the time that the call to .Fn sem_getvalue is actually run. .Sh RETURN VALUES .Rv -std sem_getvalue .Sh ERRORS The .Fn sem_getvalue function will fail if: l -tag -width Er t Bq Er EINVAL The .Fa sem argument points to an invalid semaphore. .El .Sh SEE ALSO .Xr sem_post 3 , .Xr sem_trywait 3 , .Xr sem_wait 3 .Sh STANDARDS The .Fn sem_getvalue function conforms to .St -p1003.1-96 .
p The value of the semaphore is never negative, even if there are threads blocked on the semaphore. .Tn POSIX is somewhat ambiguous in its wording with regard to what the value of the semaphore should be if there are blocked waiting threads, but this behavior is conformant, given the wording of the specification.