def string_format
      (command_environment.map do |key, value|
        [key, value].join("=")
      end + [command]).join(" ")
    end
def string_format
      (command_environment.map do |key, value|
        [key, value].join("=")
      end + [command]).join(" ")
    end
The command as a string, including arguments and options, plus prefixed
 environment variables.