NAME    [Toc]    [Back]

     sem_getvalue - get the value of a semaphore

SYNOPSIS    [Toc]    [Back]

     #include <semaphore.h>

     int
     sem_getvalue(sem_t *sem, int *sval);

DESCRIPTION    [Toc]    [Back]

     The sem_getvalue() function sets the variable pointed to  by
sval to the
     current  value of the semaphore pointed to by sem, as of the
time that the
     call to sem_getvalue() is actually run.

RETURN VALUES    [Toc]    [Back]

     The sem_getvalue() function returns the value 0 if  successful; otherwise
     the  value  -1  is returned and the global variable errno is
set to indicate
     the error.

ERRORS    [Toc]    [Back]

     sem_getvalue() will fail if:

     [EINVAL]      sem points to an invalid semaphore.

SEE ALSO    [Toc]    [Back]

     sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS    [Toc]    [Back]

     sem_getvalue() conforms to ISO/IEC 9945-1:1996  (``POSIX'').

     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.

OpenBSD      3.6                        February     15,     2000