int
sem_wait(sem_t *sem)
int
sem_trywait(sem_t *sem)
)
function decrements (locks) the semaphore pointed to by
sem,
but blocks if the value of
sem
is zero, until the value is non-zero and the value can be decremented.
The
sem_trywait()
function decrements (locks) the semaphore pointed to by
sem
only if the value is non-zero.
Otherwise, the semaphore is not decremented and an error is returned.
)
and
sem_trywait()
will fail if:
EINVAL]sem
points to an invalid semaphore.
Additionally,
sem_trywait()
will fail if:
EAGAIN])
and
sem_trywait()
conform to
ISO/IEC 9945-1:1996 (``POSIX.1'') .