Return Values
sem_trywait() returns zero after completing successfully.
Any other return value indicates that an error occurred. When any of the following
conditions occurs, the function fails and returns the corresponding value.
-
EINVAL
-
sem
points to an illegal address.
-
EINTR
-
A signal interrupted this function.
-
EAGAIN
-
The semaphore was already locked,
so it cannot be immediately locked by the sem_trywait()
operation.