if(i == components->end()) {

	// nothing matched

      std::string ComponentName(name); 

      std::string errorMessage = "Logging component \""+ComponentName+"\" not found. See above for a list of available log components";

      LogComponentPrintList();

      NS_FATAL_ERROR (errorMessage.c_str());

    }

static bool ComponentExists(std::string componentName) 

{

  char const*name=componentName.c_str();

  ComponentList *components = GetComponentList ();

  ComponentListI i;

  for ( i = components->begin ();

        i != components->end ();

        i++)

     {

       if (i->first.compare (name) == 0) 

 	{

	  return true;

 	}

    }

  if(i == components->end()) {	// nothing matched 

	return false;    

   }

  else {

    NS_ASSERT(1==0);			// the control should never reach here. 

  }

}

static void checkEnvironmentVariables() {

#ifdef HAVE_GETENV

  char *envVar = getenv ("NS_LOG");

  if (envVar == 0)

    {

      return;

    }

  std::string env = envVar;

  std::string::size_type cur = 0;

  std::string::size_type next = 0;

  while (next != std::string::npos)

    {

      next = env.find_first_of (":", cur);

      std::string tmp = std::string (env, cur, next-cur);

      std::string::size_type equal = tmp.find ("=");

      std::string component;

      if (equal == std::string::npos)		// ie no '=' characters found 

        {

          component = tmp;

          if (ComponentExists(component) || component == "*")

            {

              return;

            }

	  else {

	      LogComponentPrintList();

              std::string errorMessage="Invalid or unregistered component name \""+component+"\" in env variable NS_LOG, see above for a list of valid components";

	      NS_FATAL_ERROR(errorMessage.c_str());

	  }

        }

      else

        {

          component = tmp.substr (0, equal);

          if (ComponentExists(component) || component == "*")

            {

              std::string::size_type cur_lev;

              std::string::size_type next_lev = equal;

              do

                {

                  cur_lev = next_lev + 1;

                  next_lev = tmp.find ("|", cur_lev);

                  std::string lev = tmp.substr (cur_lev, next_lev - cur_lev);

                  if (    (lev == "error")

		      ||  (lev == "warn")

                      || (lev == "debug")

                      || (lev == "info")

                      || (lev == "function")

                      || (lev == "logic")

                      || (lev == "all")

                      || (lev == "prefix_func")

                      || (lev == "prefix_time")

                      || (lev == "prefix_node")

                      || (lev == "level_error")

                      || (lev == "level_warn")

                      || (lev == "level_debug")

                      || (lev == "level_info")

                      || (lev == "level_function")

                      || (lev == "level_logic")

                      || (lev == "level_all")

		     ) continue;

		  else {

 			std::string errorMessage="Invalid log level \""+lev+"\" in env variable NS_LOG for component name " + component;

			NS_FATAL_ERROR(errorMessage.c_str());	

		  }

                } while (next_lev != std::string::npos);

            }

	    else 

	     {

	      LogComponentPrintList();

	      std::string errorMessage="Invalid or unregistered component name \""+component+"\" in env variable NS_LOG, see above for a list of valid components";

	      NS_FATAL_ERROR(errorMessage.c_str());

	    }

        }

      cur = next + 1;	// parse next component

    }

#endif

}

  checkEnvironmentVariables();