sem_getvalue - get the value of a semaphore
sem_getvalue(sem_t *sem, int *sval);
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.
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
sem_getvalue() will fail if:
[EINVAL] sem points to an invalid semaphore.
sem_post(3), sem_trywait(3), sem_wait(3)
sem_getvalue() conforms to ISO/IEC 9945-1:1996 (``POSIX'').
The value of the semaphore is never negative, even if there
blocked on the semaphore. POSIX is somewhat ambiguous in
with regard to what the value of the semaphore should be if
blocked waiting threads, but this behavior is conformant,
given the wording
of the specification.
OpenBSD 3.6 February 15, 2000
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