1SEM_GETVALUE(P)            POSIX Programmer's Manual           SEM_GETVALUE(P)
2
3
4

NAME

6       sem_getvalue - get the value of a semaphore (REALTIME)
7

SYNOPSIS

9       #include <semaphore.h>
10
11       int sem_getvalue(sem_t *restrict sem, int *restrict sval);
12
13

DESCRIPTION

15       The sem_getvalue() function shall update the location referenced by the
16       sval argument to have the value of  the  semaphore  referenced  by  sem
17       without  affecting the state of the semaphore. The updated value repre‐
18       sents an actual semaphore value that occurred at some unspecified  time
19       during  the  call, but it need not be the actual value of the semaphore
20       when it is returned to the calling process.
21
22       If sem is locked, then the object to which sval points shall either  be
23       set to zero or to a negative number whose absolute value represents the
24       number of processes waiting for the semaphore at some unspecified  time
25       during the call.
26

RETURN VALUE

28       Upon  successful completion, the sem_getvalue() function shall return a
29       value of zero. Otherwise, it shall return a value of -1 and  set  errno
30       to indicate the error.
31

ERRORS

33       The sem_getvalue() function shall fail if:
34
35       EINVAL The sem argument does not refer to a valid semaphore.
36
37
38       The following sections are informative.
39

EXAMPLES

41       None.
42

APPLICATION USAGE

44       The  sem_getvalue()  function is part of the Semaphores option and need
45       not be available on all implementations.
46

RATIONALE

48       None.
49

FUTURE DIRECTIONS

51       None.
52

SEE ALSO

54       semctl() , semget() , semop() , sem_post() , sem_timedwait() , sem_try‐
55       wait()    ,    sem_wait()    ,   the   Base   Definitions   volume   of
56       IEEE Std 1003.1-2001, <semaphore.h>
57

59       Portions of this text are reprinted and reproduced in  electronic  form
60       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
61       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
62       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
63       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
64       event of any discrepancy between this version and the original IEEE and
65       The Open Group Standard, the original IEEE and The Open Group  Standard
66       is  the  referee document. The original Standard can be obtained online
67       at http://www.opengroup.org/unix/online.html .
68
69
70
71IEEE/The Open Group                  2003                      SEM_GETVALUE(P)
Impressum