使用ifstream读取.txt并使用ofstream写入新的.txt文件，但只有第一行有效

#include <fstream>
#include <iostream>

int main() {
    std::ifstream inputFile("input.txt");
    if (!inputFile) {
        std::cerr << "Failed to open input.txt" << std::endl;
        return 1;
    }
    // 读取文件内容...
    inputFile.close();
    return 0;
}

#include <fstream>
#include <iostream>

int main() {
    std::ifstream inputFile("input.txt");
    if (!inputFile) {
        std::cerr << "Failed to open input.txt" << std::endl;
        return 1;
    }

    std::ofstream outputFile("output.txt");
    if (!outputFile) {
        std::cerr << "Failed to open output.txt" << std::endl;
        return 1;
    }
    // 读取文件内容并写入新文件...
    inputFile.close();
    outputFile.close();
    return 0;
}

#include <fstream>
#include <iostream>
#include <string>

int main() {
    std::ifstream inputFile("input.txt");
    if (!inputFile) {
        std::cerr << "Failed to open input.txt" << std::endl;
        return 1;
    }

    std::ofstream outputFile("output.txt");
    if (!outputFile) {
        std::cerr << "Failed to open output.txt" << std::endl;
        return 1;
    }

    std::string line;
    if (std::getline(inputFile, line)) {
        outputFile << line;
    }

    inputFile.close();
    outputFile.close();
    return 0;
}