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Re: Can popen2 be avoided?


From: John S. Gwynne
Subject: Re: Can popen2 be avoided?
Date: Wed, 06 Sep 2000 16:58:05 -0400

| I have trouble using popen-close (see bug-octave 2000-276) and popen2( see
| help-octave 2000-722).
| For my students, I'm making some simulations, where the calculations are
| done in octave, but the interface is in Tcl/Tk.
| 
| The interface (which I start with popen from octave), is perfectly able to
| send strings to octave, but I would like the output of octave to be shown in
| the same interface, not to stdout. Since I can't get popen2 to work, is
| there another way to send the output of octave to the interface? I'm not
| very familiar with communicating between processes (as you might have
| noticed...), so...can someone help me?
| 
| Thanks,
| Stef.

FWIW, I had the same problem with popen2. I ended up using a socket 
pair for two-way communication with an external application.

The simple interface has four operations: 0: close, 1: open, 2: read, 
3: write. The first write specifies the appliction to run.

socketID = socket(1); // create socket
status = socket(3, socketID, appName); // start application appName
status = socket(3, socketID, sendString); // send to stdin of app
[msg status] = socket(2, socketID, timeout, termChar); // receive from 
                        // stdout of app terminated by either a
                        // timeout of the character termChar.
status = socket(0,socketID); // close socket

It's pretty simple, but it worked for what I was doing (no guarantees
and no security).... an interface between octave and a root
(http://root.cern.ch/root) based gui.

if you want to have a look, try 
 ftp://jsgpc.mrcday.com/pub/octave/octaveSockets.tar.gz

john gwynne



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