C/C++中文件的随机读写详解及其作用介绍

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

int main() {
    int a[10], b[10];
    
    // 打开文件
    fstream iofile("temp.txt", ios::in | ios::out);
    if(!iofile) {
        cerr << "open error!" << endl;
        exit(1);
    }
    
    // 写入文件
    cout << "enter 10 integer numbers:\n";
    for (int i = 0; i < 10; ++i) {
        cin >> a[i];
        iofile << a[i] << " ";
    }
    
    // 读取文件
    cout << "The numbers have been writen to file." << endl;
    cout << "Display the data by read from file:" << endl;

    iofile.seekg(0, ios::beg);
    for (int i = 0; i < 10; ++i) {
        iofile >> b[i];
        cout << b[i] << " ";
    }
    iofile.close();

    return 0;
}

#include <fstream>
#include <iostream>
#include "Student.h"
using namespace std;

int main() {
    // 打开文件
    fstream iofile("student.txt",ios::in|ios::out);
    if(!iofile) {
        cerr << "open error!" << endl;
        exit(1);
    }

    // 向磁盘文件输出2个学生的数据
    Student stud[2]{
            {1, "Little White"},
            {2, "Big White"}
    };

    for (int i = 0; i < 2; ++i) {
        iofile.write((char *) &stud[i], sizeof(stud[i]));
    }
    // 读取学生数据，并显示
    Student read[2];
    for (int i = 0; i < 2; ++i) {
        iofile.seekg(i*sizeof(stud[i]),ios::beg);
        iofile.read((char *)&read[i],sizeof(read[0]));
    }

    // 修改第2个学生的数据后存回文件原位置
    stud[1].setId(1012); //修改
    stud[1].setName("Wu");
    iofile.seekp(sizeof(stud[0]),ios::beg);
    iofile.write((char *)&stud[1],sizeof(stud[2]));
    iofile.seekg(0,ios::beg);


    // 读入修改后的2个学生的数据并显示出来
    for(int i=0; i<2; i++)
    {
        iofile.read((char *)&stud[i],sizeof(stud[i]));
        stud[i].display();
    }
    iofile.close( );
    return 0;
}