Similar to intersect.pl but in ruby. This version just reads files "file1 file2 file3".

intersect.rb

#!/usr/bin/env  ruby
require 'digest/sha1'

# Build an array of hashes for each file, using sha1 of line as key
def get_digests_for_file(file_name)
  h = {}
  File.readlines(file_name).each do |line|
    h[Digest::SHA1::digest line] = line
  end
  h
end

h1 = get_digests_for_file("file1")
h2 = get_digests_for_file("file2")
h3 = get_digests_for_file("file3")

# Using set intersections, build a array of keys found in all 3 files
keys_in_all_files = h1.keys & h2.keys & h3.keys

# Print the found lines
keys_in_all_files.each {|k| puts h1[k]}