old_contents: #!/bin/sh
  
  tailf /tmp/irssitail | ./irssi-chanformat.py | ./irssi-chanshift.py | ./irssi-colorize.py >>/tmp/feed
  
new_contents: #!/bin/sh
  
  if [ ! -e /tmp/irssitail ]; then
      touch /tmp/irssitail
  fi
  
  tailf /tmp/irssitail | ./irssi-chanformat.py | ./irssi-chanshift.py | ./irssi-colorize.py >>/tmp/feed
  
subject: create /tmp/irssitail if not exists yet