# File lib/rubygems/commands/specification_command.rb, line 57
  def execute
    specs = []
    gem = options[:args].shift

    unless gem then
      raise Gem::CommandLineError,
            "Please specify a gem name or file on the command line"
    end

    dep = Gem::Dependency.new gem, options[:version]

    field = get_one_optional_argument

    if field then
      field = field.intern

      if options[:format] == :ruby then
        raise Gem::CommandLineError, "--ruby and FIELD are mutually exclusive"
      end

      unless Gem::Specification.attribute_names.include? field then
        raise Gem::CommandLineError,
              "no field %p on Gem::Specification" % field.to_s
      end
    end

    if local? then
      if File.exist? gem then
        specs << Gem::Format.from_file_by_path(gem).spec rescue nil
      end

      if specs.empty? then
        specs.push(*Gem.source_index.search(dep))
      end
    end

    if remote? then
      found = Gem::SpecFetcher.fetcher.fetch dep

      specs.push(*found.map { |spec,| spec })
    end

    if specs.empty? then
      alert_error "Unknown gem '#{gem}'"
      terminate_interaction 1
    end

    output = lambda do |s|
      s = s.send field if field

      say case options[:format]
          when :ruby then s.to_ruby
          when :marshal then Marshal.dump s
          else s.to_yaml
          end

      say "\n"
    end

    if options[:all] then
      specs.each(&output)
    else
      spec = specs.sort_by { |s| s.version }.last
      output[spec]
    end
  end