[Tutor] pass argument into running program *outside* of program

[Emile van Sebille]

Lie Ryan wrote:
> 
> In a much simpler situation, even a communicating from a plain file
> could be enough. In the daemon's program folder, there'll be two files:
> input and output. You write to input to instruct the server and read the
> response from output. This model is in respect to Unix's philosophy:
> "make program to handle text streams, because it's the universal
> interface".
> 

I've done this and it works well... one thing to watch out for though is 
snagging a file before it's completely written.  Setting up a semaphore 
or pausing to allow the file write to complete once seeing the file 
fixes it adequately.

Emile