gistfile1.rb

#!/usr/bin/env ruby

out_path = ARGV[0]
in_path = ARGV[1]

glob = "#{in_path}/**/*.coffee"
cmd = "coffee -o #{out_path} -c #{in_path}"

current_mtime = Time.now

def modified?(glob)
  mtime = last_mtime(glob)
  if current_mtime != mtime
    current_mtime = mtime
    true
  else
    false
  end
end

def last_mtime(glob)
  Dir[glob].map { |f| File.mtime(f) }.max
end

loop do
  if modified?(glob)
    puts "Recompiling..."
    system(cmd)
  end
end