即使输入文件不存在，输出文件仍会继续创建？ ****编辑****

Question

我正在尝试编写一个程序，将文件的第一行移动到一个新文件中。我的目标是，如果输入文件不存在，则不会创建新文件。我得到它来阅读.good()所以我得到输入失败的消息。但是，我无法创建新文件。

以下是代码：

int main()
{
        fstream inFile;
        fstream outFile;;
        string fileName("");
        string destName("");

        cout << "Please enter file name: ";
        cin >> fileName;
        cout << endl;

        cout << "Please enter file name of destination: ";
        cin >> destName;
        cout << endl;

        inFile.open(fileName, ios::in);
        outFile.open(destName, ios::out);

        getline(inFile, fileName);

        if (inFile.good() != true) { 
                cout << "?Unable to input file!\n" << endl; 
                return 0;
        }   

        else {
                outFile << fileName << endl;
                return 0;
        }   

        if (outFile.good() == true) {

                cout << "?File '" << destName << "' already exists!\n" << endl;
                return 0;
        }   

        inFile.close();
        outFile.close();

        return 0;
}

有人可以帮忙吗？

提前谢谢。

感谢您之前的帮助，

*****编辑*****

我现在很好奇。如果输出文件已经存在，我想做一个错误陈述。但是，如果文件存在或不存在，我仍然会收到错误。我试图将outFile.open移到底部，以便在检查之前创建文件，但它仍然说它已经存在？

int main()

{
        fstream inFile;
        fstream outFile;;
        string fileName("");
        string destName("");

        cout << "Please enter file name: ";
        cin >> fileName;
        cout << endl;

        inFile.open(fileName, ios::in);

        getline(inFile, fileName);

        if (inFile.good() != true) { 
                cout << "?Unable to input file!\n" << endl; 
                return 0;
        }   

        cout << "Please enter file name of destination: ";
        cin >> destName;
        cout << endl;


        if (outFile.good() == true) {

                cout << "?File '" << destName << "' already exists!\n" << endl;
                return 0;
        }   

        outFile.open(destName, ios::out);    
        outFile << fileName << endl;


        inFile.close();
        outFile.close();

        return 0;
}

Answer 1

您需要在输入文件检查后将输出文件的打开调用移动到。

这样的事情：

int main()
{
        fstream inFile;
        fstream outFile;;
        string fileName("");
        string destName("");

        cout << "Please enter file name: ";
        cin >> fileName;
        cout << endl;

        cout << "Please enter file name of destination: ";
        cin >> destName;
        cout << endl;

        inFile.open(fileName, ios::in);

        getline(inFile, fileName);

        if (inFile.good() != true) { 
                cout << "?Unable to input file!\n" << endl; 
                return 0;
        }   


        outFile.open(destName, ios::out);
        outFile << fileName << endl;`enter code here`        

        if (outFile.good() == true) {

                cout << "?File '" << destName << "' already exists!\n" << endl;
                return 0;
        }   

        inFile.close();
        outFile.close();

        return 0;
}