为什么我的程序不备份我的文件？

Question

我正在处理一个 C++ 项目，我需要在同一个程序中创建数据文件后对其进行备份。我已经创建了数据文件并成功地向其中写入了文本，但是，当我尝试使用我编写的函数备份同一个文件时，它不起作用。

这是函数后面的一些上下文：

我创建的文件名为 contactList.ext（.ext，所以它是在当前目录中创建的）。当提示输入此程序中的文件名时，我输入 contactList 并成功打开，但是，我遇到的唯一问题是它不会备份文件。我试图以这种方式备份它： newFileName = (fileName + ".bak");

我不知道还有什么其他方法可以使用 c++ 备份文件。非常感谢任何帮助！

void backupDataFile() {
    string fileName;
    string newFileName;
    string line;
    int contactListSize = 10, i = 0;
    string contacts[contactListSize];
    char userResponse;
    fstream inFile, outFile;

    cout << "\nEnter the name of the file you want to backup: ";
    cin >> fileName;

    inFile.open(fileName.c_str()); //attempts to open file

    //file fails to open
    if (inFile.fail()) {
        cout << "\nThe file " << fileName << " was not opened successfully."
             << "\n Please check that the file currently exists.\n";
        exit(1);
    }

    //read and display contents of file & assign each line to an array
    cout << "\nThe following is the contents of " << fileName << ":\n\n";

    while(getline(inFile, line)) {
        cout << line << endl;
        contacts[i] = line; //assigns each line to an array position
        i++;
    }
    inFile.close(); //closes existing file allowing the opening of a new file

    //verify user wishes to backup file
    cout << "\nWould you like to backup this file? <y/n>: ";
    cin >> userResponse;

    if (userResponse == 'y') {
        newFileName = (fileName + ".bak"); //assigns name of backup file

        outFile.open(newFileName.c_str()); //attempts to open backup file

        //file fails to create
        if (outFile.fail()) {
            cout << "\nThe file " << fileName << " did not backup successfully.";
            exit(1);
        }
        ///fix hereafter
        else { //writes contents from contactList.ext to contactList.bak
            while (i < 10) {
            cout << contacts[i] << endl; //writes each contact into new file
            i++;
            }
            //for (int j = 0; j < 10; j++) {
              //  outFile << contacts[j] << endl;
        }
        outFile.close(); //closes file

        cout << "\nThe file " << fileName << " has been backed-up successfully."
             << "\nThe backup file is named " << newFileName;
    }//end outer-if
    else
        cout << "\nYou will be directed back to the Main Menu.";
}

Answer 1

你的问题出在这两个部分。

 while (i < 10) {
            cout << contacts[i] << endl; //writes each contact into new file
            i++;
            }
            //for (int j = 0; j < 10; j++) {
          //  outFile << contacts[j] << endl;

for 循环不应被注释掉，您只是在需要写入输出文件时才写入控制台（使用 cout）。

调用outFile.out()时还需要指定ios::out。

outFile.open(newFileName.c_str(),ios::out)

Answer 2

正如另一位发帖人所述，您实际上运行并不是输出到文件

的代码

//outFile << contacts[j] << endl;

然而我看到的另一个问题是只要i小于10你就循环输出。这很好，但是你在读取文件时计算行数后没有将i设置回0 ！这意味着您的

while(i < 10) {

循环永远不会运行:)

为什么我的程序不备份我的文件？

why won't my program back up my file?

c++

backup