c++ 输入/输出流

#include <iostream>
#include <fstream>
#include <sstream>

int main() {
  std::ifstream file("in.txt");
  if (!file.is_open()) {
    std::cerr << "can't open file" << std::endl;
    return 1;
  }

  std::stringstream ss;
  ss << file.rdbuf();
  file.close();

  int x;
  while (ss >> x) {
    std::cout << x << std::endl;
  }

  return 0;
}