Question

我正在开发一个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，并且已经成功地将文本写入其中，但是，当我尝试使用我编写的函数备份同一个文件时，它无法正常工作。

以下是函数后面的一些上下文：

我创建的文件名名为contactList.ext（.ext，因此它在当前目录中创建）。当我在此程序中提示输入文件名时，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。我尝试以这种方式备份它：newFileName =（fileName +＆＃34; .bak＆＃34;）;

我不知道使用c ++备份文件的其他方式。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

你的问题在于这两个部分。

 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;

不应该注释for循环，当你需要写入outfile时，你只需要写入控制台（使用cout）。

调用outFile.out（）时还需要指定ios :: out。

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

Answer 2

正如另一张海报所述，你实际上并没有运行输出到文件的代码

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

然而我看到的另一个问题是只要我小于10就输出一个循环。这很好，但是在读取文件后计算行数后你没有将i设置回0 ！这意味着你的

while(i < 10) {

循环从不运行：）

为什么我的程序会备份我的文件？

2 个答案: