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
";
        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 0;
}

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[10];
    int num;
    int age;
    char addr[20];
    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 = 1; i <= 3; 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 << "
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 0;
}

结果：