Re: [Closed REQ 5808]: external modules

[daemon]

> hi,
> can i run a fortran or c code (external module) in a different machine
> on a different network and pipe the data to geomview running on my
> workstation?
> 
> i think the present version of geomview needs me to run the external
> module through the geomview package.
> 
> i am using a sunsparc machine running sunOS 4.1.3 for running the
> geomview package.

Yes, there are a couple of simple ways to do this even with the current
version of geomview.

If it's convenient to start the process from geomview, you can write
an external-module definition like:

(emodule-define MyProgram 'rsh othermachine myprogram')   or
(emodule-define MyProgram 'rsh othermachine "cd somedirectory; myprogram"')

and let rsh (the remote-shell command) take care of connecting myprogram's
standard input and output to geomview.  If the program has, say, an
X-window interface of its own, you'd presumably have to tell it which
display you're on, as in

(emodule-define MyProgram 'rsh othermachine "cd somedirectory; env DISPLAY=`hostname`:0 myprogram"')

Note that the choice of quotes is important: the
	rsh othermachine " ... "
must use double-quotes, so that `hostname` is expanded on the machine
where geomview runs (where presumably the display is, too).  Single-quotes
would expand it on othermachine instead.


On the other hand, you may find it easier to invoke your program and have it
start a copy of geomview.  If your program doesn't need to receive
responses from geomview, you could have it open a pipe to

   rsh geomviewmachine "env DISPLAY=:0 togeomview -c"

Here "togeomview" is a program which creates a named pipe, invokes a copy of
geomview if none is already running (and already listening to that pipe),
and sends its standard input to the same pipe.  Use "togeomview -g" if you're
sending geometric data directly, or "togeomview -c" if you send GCL commands.

The "env DISPLAY=:0" above assumes that geomview should display on the machine
where it's invoked, i.e. that you sit at geomviewmachine's console,
use e.g. rlogin to invoke your program, which in turn rsh's back to
the machine where you're sitting to invoke geomview.  Graphics are much
faster when geomview runs and displays on the same machine.

If you're writing in C, you could do the above via the "popen()" library
routine, as in

   FILE *togv;

   togv = popen("rsh geomviewmachine \"env DISPLAY=:0 togeomview -c\"", "w");

   ...
   fprintf(togv, " ... ", ...);

   ...
   pclose(togv);

Finally, if the program does need to read responses from geomview, 
and you don't want it to run as an external module initiated from geomview
via rsh as above, you'll need to set up a pair of connections and use
geomview's "command" command to read and write a pair of named pipes.
This is more involved, and I won't try to explain it unless you need
that arrangement.