runoob_04_fstream

/*
 * @Author: by777
 * @Date: 2025-03-21 16:30:18
 * @LastEditors: by777
 * @LastEditTime: 2025-03-21 16:37:38
 * @FilePath: /cxx_stl/runoob_04.cpp
 * @Description: https://www.runoob.com/cplusplus/cpp-libs-fstream.html
 * 
 * Copyright (c) 2025 by by777, All Rights Reserved. 
 */
#include <iostream>
#include <fstream>
int main(int argc, const char** argv) {
    std::fstream file;
    auto mode = std::ios::out; // 以输出模式打开文件
    file.open("myfile", mode);
    if(!file){
        std::cerr<<"unable to open file"<<std::endl;
        return 1;
    }
    file<<"Hello fstream!"<<std::endl;
    file.close();

    mode = std::ios::in; // 以输入模式打开文件
    file.open("myfile", mode);
    std::string line;
    std::cout<<"-------------------"<<std::endl;
    while(getline(file, line)){
        // 逐行读取
        std::cout<<line<<std::endl;
    }
    file.close();

    mode = std::ios::app; // 以输入模式打开文件
    file.open("myfile", mode);
    std::cout<<"-------------------"<<std::endl;
    file<<"this is append mode"<<std::endl;
    file.close();



    return 0;
}