word-match.rb

require 'set'

# information about a single line
LineInfo = Struct.new :file_name, :lineno, :line

# comparison data
FileData = Struct.new :file_a, :file_b

# read all words from first file and store in a Set
words = File.foreach(ARGV.shift).map {|l| l.chomp!}.to_set.freeze

# storage for maintaining matches
matches = Hash.new {|h,words| h[words] = FileData.new [], []}

# read first file
f = ARGV.shift
File.foreach f do |line|
  w = words & line.scan(/\w+/)
  matches[w].file_a << LineInfo.new(f, $., line) unless w.empty?
end

# read second file
f = ARGV.shift
File.foreach f do |line|
  w = words & line.scan(/\w+/)
  matches[w].file_b << LineInfo.new(f, $., line) unless w.empty?
end

# output matches
matches.each do |words, file_data|
  unless file_data.file_a.empty? || file_data.file_b.empty?
    p words, file_data
    puts
  end
end