Grepping XML using XPath

xgrep.rb

#!/usr/bin/env ruby

# Usage:
#   xgrep.rb '//load[@module]/@module' autoload_configs/modules.conf.xml

require 'nokogiri'

xpath = ARGV[0]
files = ARGV[1..-1]

def output(results)
  case results
  when Nokogiri::XML::Attr
    puts results.value
  when Array, Nokogiri::XML::NodeSet
    results.each{|result| output(result) }
  when String
    puts results
  else
    puts "The following are the contents I couldn't handle"
    p results
    abort "Don't know how to handle #{results.class}, please fix me."
  end
end

files.each do |file|
  File.open(file) do |io|
    output(Nokogiri::XML(io).xpath(xpath))
  end
end