How to copy files in Visual C++?

Question

I am using Visual C++. How to copy the content of this file to another file?

UINT32 writeToLog(wstring log)
 {
    wfstream file1 (LOG_FILE_NAME, ios_base::out);  
    file1 << log;       
    file1.close();

     // want to copy file1 to file2

     return 0;
 }

Answer 1

Standard C++ has no file copying facility, other than reading the file into memory and writing it out again to a different file. As you are using Windows, you can use the CopyFile function - other OSs have similar, OS-specific functions.

Answer 2

What exactly do you want to do? If you need a copy of the data, you can read it in and write it back out again. If you really need a copy of the file, you have to use OS specific calls.

In many cases, reading in the file data and then writing it out again to a different file is a close enough approximation to a copy - like this:

ifstream file1(...);
ofstream file2(...);
std::copy(istream_iterator<char>(file1),istream_iterator<char>(),ostream_iterator<char>(file2));

However that really isn't a copy - it's creating a new file with the same contents. It won't correctly handle hard links or symlinks, it won't correctly handle metadata and it will only 'copy' the default file stream.

If you need a file copy on Windows you should call one of CopyFile, CopyFileEx or CopyFileTransacted depending on your exact requirements.