shell

#include <iostream>
#include <string>
#include <cstdlib>
int main() {
  std::string line;
  for ( ; ; ) {
    std::cout << "$> ";
    std::getline(std::cin, line);
    if ( line == "end" || std::cin.eof() ) break;
    std::system(line.c_str());
  }
  return 0;
}