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Re: How to communicate with a running external process with

From: Buchs, Kevin J.
Subject: Re: How to communicate with a running external process with
Date: Mon, 22 Jul 2013 15:27:06 +0000


Your questions and responses suggest that maybe you are not grasping some 
basics of interprocess communication. You have some other program running in 
another process, not started by emacs and you want to communicate with it. A 
critical factor in such communication will be knowing how that other program is 
set up to communicate. Some programs are developed to have standard 
communication ports and protocols, like HTTP. Unix/Linux supports signals 
(kill) which a program may be set up accept and respond appropriately toward. A 
program may support TCP/IP or Unix sockets. A program may read and write files. 
You might have shared memory space or semaphores. There are dozens of different 
mechanisms. Emacs supports some of them out of the box. It might be that you 
can extend emacs by writing code to support other mechanisms. Another 
alternative is for emacs to communicate with a subprocess it creates running a 
program designed to communicate with the other process. However, what does the 
other program support? This is the question you need to answer. We can't make 
up an answer for you.

As an analogy, if you and I wish to speak, we may need to speak face to face. 
If we don't speak the same language we have trouble. Maybe we can talk on the 
telephone, but if you don't have a telephone, we are not going to speak that 
way. Communication takes appropriate coordination for the sender and receiver. 

Kevin Buchs | Senior Engineer | SPPDG | 507-538-5459 |
Mayo Clinic | 200 First Street SW | Rochester, MN 55905 |

-----Original Message-----
> How would you communicate with the external process, from any other
> program?

I don't know, and I interpreted the responses so far to my post as "it
is impossible, only 'kill' can access the running external process with
given PID" - but kill sends signals, no command-strings or so. 

So when suggestions arrive like 'use plain socket communication' I'm
still curious if there is a 'magic hack' to achieve that, given that the
external process is NO Emacs subprocess and already running.

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