Question

The following code will print something to a file

    std::fstream fout ("D_addr.txt", std::fstream::app);
    fout <<  pkt->Addr() << std::endl;
    flush(fout);
    fout.close();

While debugging, I watched pkt->Addr() and it has some values. The fout line is passed without problem. Also the file D_addr.txt is created. However after closing the file, the file size is zero! nothing has been written to it.

Where is the problem?

Answer 1

This is not your actual code I guess and if it is I would start with that Addr() function of yours.

Note that fstream::close “closes the file currently associated with the object, disassociating it from the stream. Any pending output sequence is written to the physical file.” flush(fout); can be omitted.

You should also specify std::fstream::out flag. “If the function is called with any value in that parameter the default mode is overridden, not combined.” So instead of std::fstream::app you should pass std::fstream::app | std::fstream::out.