run command automatically when specified file was modified

jamie

#!/usr/bin/env ruby

if ARGV.size < 2
  puts "Usage: jamie file command" 
  exit(0)
end

target = ARGV[0]
cmd    = ARGV[1]

last_mtime = File.mtime(target)

loop do
  sleep 1
  mtime = File.mtime(target)

  if mtime > last_mtime
    puts "The file was modified ..."
    system(cmd)
    last_mtime = mtime
    puts ""
  end
end