c++文件输入输出流fstream，对输入>>和输出<<重载

1. fstream 继承自iostream --> 要包含头文件#include<fstream>

2. 建立文件流对象

3. 打开文件夹

4. 测试是否打开成功

5. 进行读写操作

6. 关闭文件

#include<iostream>
#include<fstream>

using namespace std;

int main(){
    ifstream ifile;
    ofstream ofile;

    ifile.open("d:\\fileIn.txt");
    ofile.open("d:\\fileOut.txt");

    if (ifile.fail() || ofile.fail()){
        cerr << "open file fail\n";
        return EXIT_FAILURE;
    }

    char ch;
    ch = ifile.get();
    cout << ch << endl;
    while (!ifile.eof()){
        ofile.put(ch);
        ch = ifile.get();
    }

    ifile.close();
    ofile.close();

    int i;
    cin >> i;
    return ;
}

输入三个学生的姓名，学好，年龄和住址，并存入文件中，再从文件中读出来：

 #include<iostream>
 #include<fstream>
 using namespace std;

 class student{
 public:
     char name[];
     int num;
     int age;
     char addr[];
     friend ostream & operator<<(ostream &out, student &s);
     friend istream & operator>>(istream &in, student &s);
 };
 ostream & operator<<(ostream &out, student &s){
     out << s.name << " " << s.num << " " << s.age << " " << s.addr << endl;
     return out;
 }
 istream & operator>>(istream &in, student &s){
     in >> s.name >> s.num  >> s.age >> s.addr;
     return in;
 }
 int main(){
     ifstream ifile;
     ofstream ofile;
     ofile.open("d:\\s.txt");

     student s;
     for (int i = ; i <= ; i++){
         cout << "请输入第" << i << "个学生的姓名 学号 年龄 地址" << endl;
         cin >> s;   //调用>>运算符重载函数，输入学生信息
         ofile << s; //调用<<运算符重载函数，将学生信息写入到文件中
     }
     ofile.close();

     cout << "\n读出文件内容" << endl;
     ifile.open("d:\\s.txt");
     ifile >> s;
     while (!ifile.eof()){
         cout << s;
         ifile >> s;
     }
     ifile.close();
     int i;
     cin >> i;
     return ;
 }

结果：