get_variable
const string &value = c.get_variable(_var);
value = c.get_variable("device-name");
value = c.get_variable("subsystem");
return ((*i)->get_variable(var));
dst.append(get_variable(buffer));
const std::string &get_variable(const std::string &var);
const std::string &get_variable(const std::string &var) const;