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

[Ricardo Aráoz]

Emile van Sebille wrote:
> 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.
> 

If instead of an input/output file you use a directory this is easily 
solved. You write your request to a uniquely named file (with .in 
extension) and you read the response out of an equally named file with a 
.out extension. The server polls the directory for new .in files and 
processes them in order of creation date (you can even include a 
priorities scheme coded in the extension (e.g. .in1 to .in9 for the 
different priorities).