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.\" Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
.\" 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_r
.Sh SYNOPSIS
.Fd #include <semaphore.h>
.Ft int
.Fn sem_getvalue "sem_t *sem" "int *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
If successful,
.Fn sem_getvalue
returns 0. Otherwise, -1 is returned and
.Va errno
is set to indicate the type of
error.
.Sh ERRORS
.Fn sem_getvalue
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
.Fa sem
points to an invalid semaphore.
.El
.Sh SEE ALSO
.Xr sem_post 3 ,
.Xr sem_trywait 3 ,
.Xr sem_wait 3
.Sh STANDARDS
.Fn sem_getvalue
conforms to
.St -p1003.1-96 .
.Pp
The value of the semaphore is never negative, even if there are threads blocked
on the semaphore. 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.
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