Interrupting a continuous script

[Eric Brunel]

Julian Gollop wrote:
> I have a few programs continually processing text files on a Linux
> machine. Occasionally I need to stop them, but I don't want to use a
> keyboard interrupt because it may cause the script to stop in the middle
> of doing something.
> Does anyone know a simple way to allow me to stop the process by pressing
> a key on the keyboard - without stopping inside something crucial?

I'd use an interrupt handler on the signal SIGINT, which is sent to your 
process when you press Ctrl-C. It may sound complicated, but is in fact 
quite straightforward (as often with Python :-):

---------------------------
import sys, os, signal, time

interrupted = 0

def ctrlCHandler(*whatever):
  global interrupted
  interrupted = 1
  print "Interrupt caught. Please wait..."

signal.signal(signal.SIGINT, ctrlCHandler)
print "Something really important start"
for i in range(50): time.sleep(0.1)
print "Something really important end"
if interrupted: sys.exit()
print "Something really important start"
for i in range(50): time.sleep(0.1)
print "Something really important end"
---------------------------

Try to run this script and press Ctrl-C while it runs. You'll see it stops 
only when the "important" things are over. You'll just have to put a few 
lines like:
if interrupted: sys.exit()
at strategic places in your code, i.e. between important things.

HTH
-- 
- Eric Brunel <eric.brunel at pragmadev.com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com