80 lines
2.7 KiB
Groff
80 lines
2.7 KiB
Groff
.\" 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 ISO/IEC 9945-1 ANSI/IEEE
|
|
.Pq Dq Tn POSIX
|
|
Std 1003.1 1996 Edition.
|
|
.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.
|