Starting a third party application

[johnm at cs.uit.no]

Arild Hansen <arildh at stud.cs.uit.no> writes:

> I'm trying to make a small module that executes a third party application
> (for example gcalc or whatever). I do this using
> os.system("applicationname &") and then the program enters a while loop
> waiting for some external signal. When this signal arrives, I want the
> program to make a sys.exit(1) and terminate itself AS WELL AS the third
> party application it started. The code looks something like:
> 
> os.system("applicationame &")
> while continue:
> 	if signal:
> 		continue = FALSE
> 
> 
> My problem is that when the program gets the signal and terminates, the
> third party application is still running. How do I solve this problem?

Maybe you should take a look at fork, exec, kill and wait (or spawn if
you use one of the MS Windows variants). This example should do
something similar:

import os
import time

child = os.fork()
if child:
    print "blabla"
    time.sleep(2)
    os.kill(child, 3) # or some other signal
    os.wait(child)
else:
    print "Child, starting /bin/sleep"
    os.execv("/bin/sleep", ["/bin/sleep", "32"])
    os.exit(-1) # Shouldn't happen, but in case exec fails