Re: Why doesn't this code work?

From:

Ulrich Eckhardt <eckhardt@satorlaser.com>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 31 Oct 2006 16:58:04 +0100

Message-ID:

<dd8k14-58d.ln1@satorlaser.homedns.org>

Rudolfs.Bundulis@gmail.com wrote:

As I understood it's better to use fstream instead of fstream.h.

fstream.h is nonstandard. If you find any source still teaching it, dump it
and claim your money back.

outFile.open(argv[2],std::ios_base::in);// the second argument is the
output file
        if (! outFile)
        {//file does not exist
                outFile.open(argv[2],std::ios::out);
                cout<<"Testing...";
        }

Streams have a state, which is what you test when using them in a boolean
context ("if(!outFile)"). This state is never(!) reset by the stream
itself, not even when you close and open another file. Therefore, you have
to reset it explicitly using clear().

        else
        {
                cout<<"Warning: Output file already exists!\n";
                outFile.close();
                outFile.open(argv[2],std::ios::out);
                cout<<"Testing...";
        }

Note that the last two lines of both branches are equal. Further, even those
lack a test whether opening succeeded. You would have immediately seen that
once opening for input failed, opening for output fails, too.

outFile.close();

You don't have to do this, streams will close themselves when their dtor is
called.

Uli