json_inspector.rb

require 'rubygems'
require 'json'
def inspect_file(file)
  elements = {}
  while line = file.gets
    parts = line.split("\t")
    elements[parts[1]] ||=[]
    j = JSON.parse(parts.last)
    j.keys.each do | key |
      elements[parts[1]] << key unless elements[parts[1]].index(key)
      if j[key].is_a?(Array) || j[key].is_a?(Hash)
        next if j[key].is_a?(Array) and !j[key].first.is_a?(Hash)
        elements[key] ||=[]
        if j[key].is_a?(Array)
          j[key].each do |child|
            child.keys.each do |c|
              elements[key] << c unless elements[key].index(c)
            end
          end
        else
          j[key].keys.each do |c|
            elements[key] << c unless elements[key].index(c)
          end
        end
      end
    end
  end

  return elements
end

file = File.new('/Volumes/External 7/shared/open-library/edition-2009-09-11.txt', 'r')
fields = inspect_file file

puts fields.inspect