Example for http://forum.ubuntuusers.de/topic/inhaltsverzeichnis-mit-bash-sed/

idx.rb

#!/usr/bin/env ruby19

require 'set'

keys = File.read(ARGV.shift).scan(/\w+/).to_set

index = Hash.new {|h,word| h[word] = Set.new}

ARGF.each do |line|
  line.scan /\w+/ do |word|
    index[word].add ARGF.lineno if keys.include? word
  end
end

keys.sort.each do |word|
  puts word, index[word].sort.join(', ')
end