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.Dd February 29, 2012
.Dt SEM_GETVALUE 3
.Os
.Sh NAME
.Nm sem_getvalue
.Nd get the value of a semaphore
.Sh LIBRARY
.Lb librt
.Sh SYNOPSIS
.In 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
.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_timedwait 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.