text: 
  
  #ifndef ROUTING_SYS_UTIL_H
  #define ROUTING_SYS_UTIL_H
  
  #include <boost/optional.hpp>
  #include <cstdlib>
  #include <string>
  
  namespace routing
  {
  inline boost::optional<std::string>
  get_env_variable(std::string const& env_name)
  {
      char const* env_var = std::getenv(env_name.c_str());
  
      if (env_var != nullptr)
      {
          return std::string(env_var);
      }
  
      return {};
  }
  };  // namespace routing
  
  #endif
  