一动不如一静

         #include <iostream>
         #include <string>

         std::cin.widen(1024);

         for (; ;)
         {
               std::string user_input;
               std::getline(std::cin, user_input, '\n');
              
               if  (!std::cin || std::cin.eof()) break;
             
               std::cerr << user_input;
         
         }