Copy file line by line

Question

I have a problem with a loop, what i want to do is copy a file, line by line. I used this code but it in the output file write one more bracket and one line.

void copyStringNewFile(ifstream& inData,ofstream& outData)
{
string x = "";

while (inData)
{
    getline(inData, x);
    outData << x << '\n';
}
}

Probably i can remove the line:

string x = "";

In the while conditions I've tried a few solution:

while (!inData.eof())    // Works similar to while (inData)

while (inData >> x)      // Delete a lot of lines

Thank you so much, and if you can explain where eof can be useful (because in loops it seems useless).

Answer 1

You are not checking the return value of getline(). When it fails, no copy should be made. Btw, you are also depending on a final '\n' in the source file, otherwise you'll have trouble copying the last line.

Here's a form that monitors successful reads properly:

void copyStringNewFile(ifstream& inData, ofstream& outData)
{
    char ch;
    while (inData >> ch)
    {
        outData << ch;
    }
}

Or if you're ready to use a more advanced form:

void copyStringNewFile(ifstream& inData, ofstream& outData)
{
    outData << inData.rdbuf();
}

Answer 2

You probably want:

while (getline(inData, x)) {
    outData << x << '\n';
}

You are seeing the last line duplicated because you are testing the stream and THEN trying to read from it; the status of the stream as "EOF" is only set after trying - and failing - to read.