Shell built-in 'pwd' implemented in Ruby

pwd.rb

#!/usr/bin/env ruby

=begin
  The concept here is to print out the current working
  directory (pwd) following i-nodes only.
=end

def pwd
  path = []
  loop do
    self_inode   = File::stat('.').ino
    parent_inode = File::stat('..').ino
    Dir::chdir('..')
    name = Dir['*'].entries.select do |e|
      File::stat(e).ino == self_inode
    end.first
    break if self_inode == parent_inode
    path.unshift(name)
  end
  return '/' + path.join('/')
end

if __FILE__ == $0
  puts pwd
end