sem_getvalue.3 (26b6c45a92c8eae91cad4a7ce8935e08d2e5d368) sem_getvalue.3 (b0a1b4f80919d734dda03410df0cabf7297dfb68)
1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
1.\" Copyright (C) 2000 Jason Evans <jasone@canonware.com>.
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30.Dd February 15, 2000
31.Dt SEM_GETVALUE 3
32.Os
33.Sh NAME
34.Nm sem_getvalue
35.Nd get the value of a semaphore
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
36.Sh LIBRARY
37.Lb libc
38.Sh SYNOPSIS
35.Sh SYNOPSIS
39.In semaphore.h
36.Fd #include <semaphore.h>
40.Ft int
37.Ft int
41.Fn sem_getvalue "sem_t * restrict sem" "int * restrict sval"
38.Fn sem_getvalue "sem_t *sem" "int *sval"
42.Sh DESCRIPTION
43The
44.Fn sem_getvalue
45function sets the variable pointed to by
46.Fa sval
47to the current value of the semaphore pointed to by
48.Fa sem ,
49as of the time that the call to
50.Fn sem_getvalue
51is actually run.
52.Sh RETURN VALUES
39.Sh DESCRIPTION
40The
41.Fn sem_getvalue
42function sets the variable pointed to by
43.Fa sval
44to the current value of the semaphore pointed to by
45.Fa sem ,
46as of the time that the call to
47.Fn sem_getvalue
48is actually run.
49.Sh RETURN VALUES
53.Rv -std sem_getvalue
50If successful,
51.Fn sem_getvalue
52returns 0. Otherwise, -1 is returned and
53.Va errno
54is set to indicate the type of
55error.
54.Sh ERRORS
56.Sh ERRORS
55The
56.Fn sem_getvalue
57.Fn sem_getvalue
57function will fail if:
58will fail if:
58.Bl -tag -width Er
59.It Bq Er EINVAL
59.Bl -tag -width Er
60.It Bq Er EINVAL
60The
61.Fa sem
61.Fa sem
62argument
63points to an invalid semaphore.
64.El
65.Sh SEE ALSO
66.Xr sem_post 3 ,
62points to an invalid semaphore.
63.El
64.Sh SEE ALSO
65.Xr sem_post 3 ,
67.Xr sem_trywait 3 ,
68.Xr sem_wait 3 ,
66.Xr sem_wait 3 ,
69.Xr sem 4
67.Xr sem_trywait 3
70.Sh STANDARDS
68.Sh STANDARDS
71The
72.Fn sem_getvalue
69.Fn sem_getvalue
73function conforms to
74.St -p1003.1-96 .
70conforms to ISO/IEC 9945-1 ANSI/IEEE
71.Pq Dq Tn POSIX
72Std 1003.1 1996 Edition.
75.Pp
76The value of the semaphore is never negative, even if there are threads blocked
73.Pp
74The value of the semaphore is never negative, even if there are threads blocked
77on the semaphore.
78.Tn POSIX
79is somewhat ambiguous in its wording with regard to
75on the semaphore. POSIX is somewhat ambiguous in its wording with regard to
80what the value of the semaphore should be if there are blocked waiting threads,
81but this behavior is conformant, given the wording of the specification.
76what the value of the semaphore should be if there are blocked waiting threads,
77but this behavior is conformant, given the wording of the specification.