# File lib/rubygems/commands/generate_index_command.rb, line 46
  def execute
    if not File.exist?(options[:directory]) or
       not File.directory?(options[:directory]) then
      alert_error "unknown directory name #{directory}."
      terminate_interaction 1
    else
      indexer = Gem::Indexer.new options[:directory]
      indexer.generate_index
    end
  end