c++ primer 5th p289页练习题自己的解答程序

#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
#include <cstdio>
using namespace std;
istream &read(istream &);
int main(int argc,char *argv[])       //argv是一个无参数的指针数组或者char*字符串
{
  string str2;
  
  read(cin);
  cout << "Enter a string:" << endl;
  cin >> str2;
  cout << str2 << endl;
  cout << "part2:" << endl;
  cout << "begin to print file's text:" << endl;
  ifstream in(argv[1]);
  read(in);

  return 0;
}

istream &read(istream & is)
{
  string str;
  while(getline(is,str))
    {
      cout << str << endl;
    }
  is.clear();   //最后is接受的是EOF，所以流的eofbit会被置位，必须要复位才可以后续使用
  return is;
}