xref: /freebsd/lib/libc/gen/sem_getvalue.3 (revision a220d00e74dd245b4fca59c5eca0c53963686325)
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28.\" $FreeBSD$
29.Dd February 15, 2000
30.Dt SEM_GETVALUE 3
31.Os
32.Sh NAME
33.Nm sem_getvalue
34.Nd get the value of a semaphore
35.Sh LIBRARY
36.Lb libc_r
37.Sh SYNOPSIS
38.In semaphore.h
39.Ft int
40.Fn sem_getvalue "sem_t *sem" "int *sval"
41.Sh DESCRIPTION
42The
43.Fn sem_getvalue
44function sets the variable pointed to by
45.Fa sval
46to the current value of the semaphore pointed to by
47.Fa sem ,
48as of the time that the call to
49.Fn sem_getvalue
50is actually run.
51.Sh RETURN VALUES
52.Rv -std sem_getvalue
53.Sh ERRORS
54.Fn sem_getvalue
55will fail if:
56.Bl -tag -width Er
57.It Bq Er EINVAL
58.Fa sem
59points to an invalid semaphore.
60.El
61.Sh SEE ALSO
62.Xr sem_post 3 ,
63.Xr sem_trywait 3 ,
64.Xr sem_wait 3
65.Sh STANDARDS
66.Fn sem_getvalue
67conforms to
68.St -p1003.1-96 .
69.Pp
70The value of the semaphore is never negative, even if there are threads blocked
71on the semaphore.  POSIX is somewhat ambiguous in its wording with regard to
72what the value of the semaphore should be if there are blocked waiting threads,
73but this behavior is conformant, given the wording of the specification.
74