md5_stream.rb

  #!/usr/bin/ruby -w
  require 'digest/md5'
  filename = 'MD5.rdoc'

  all_digest = Digest::MD5.hexdigest(File.read(filename))

  incr_digest = Digest::MD5.new()
  file = File.open(filename, 'r')
  file.each_line do |line|
    incr_digest << line
  end

  puts incr_digest.hexdigest
  puts all_digest
  __END__