如何在C++中向一个文件中添加多行？

std::fstream file;
file.open("filename.txt", std::ios::app);

if (file.is_open()) {
    // 文件成功打开，可以进行写入操作
} else {
    // 文件打开失败，处理错误情况
}

file << "Line 1" << std::endl;
file << "Line 2" << std::endl;
file << "Line 3" << std::endl;

file.close();

#include <iostream>
#include <fstream>

int main() {
    std::fstream file;
    file.open("filename.txt", std::ios::app);

    if (file.is_open()) {
        file << "Line 1" << std::endl;
        file << "Line 2" << std::endl;
        file << "Line 3" << std::endl;

        file.close();
        std::cout << "Lines added to the file." << std::endl;
    } else {
        std::cout << "Failed to open the file." << std::endl;
    }

    return 0;
}