At what point do you expect new directories to arrive? At what point would you like to be prepared to handle them? What is the larger problem, because that will give us all a clearer idea of what you are trying to achieve and what the constraints are that affect how you might get the job done.

At this point (and in light of previous posts) it seems that you are writing some sort of job dispatch system based on control files dropped into directories that serve to prioritise work. It seems most likely that what you are trying to do here is poll for new jobs. Maybe if there is anything trickier that solving that trivial problem you will let us know?

Information like "how long a job dispatch/execution takes", "what the maximum allowable latency is", "how often new directories may be added", "the range of OS's supported" and so on will help determine a best solution.