Watch directory for file changes and act.

dirwatch-example.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'directory_watcher'

dw = DirectoryWatcher.new '.'
dw.interval = 1.0
dw.add_observer do |*args| 
  args.each do |event| 
    if /file\d/ =~ event.path
      `cat file1.txt file2.txt file3.txt > files-combined.txt`
      puts "#{Time.now.strftime("%I:%M:%S")} \
      Created files-combined.txt (since #{event.path} #{event.type})"
    end
  end
end

dw.start
gets      # when the user hits "enter" the script will terminate
dw.stop