Skip lines in std::istream

Question

I\'m using std::getline() to read lines from an std::istream-derived class, how can I move forward a few lines?

Do I have to just read and discard them?

Answer 1

No, you don't have to use getline

The more efficient way is ignoring strings with std::istream::ignore

for (int currLineNumber = 0; currLineNumber < startLineNumber; ++currLineNumber){
    if (addressesFile.ignore(numeric_limits::max(), addressesFile.widen('\n'))){ 
        //just skipping the line
    } else 
        return HandleReadingLineError(addressesFile, currLineNumber);
}

HandleReadingLineError is not standart but hand-made, of course. The first parameter is maximum number of characters to extract. If this is exactly numeric_limits::max(), there is no limit: Link at cplusplus.com: std::istream::ignore

If you are going to skip a lot of lines you definitely should use it instead of getline: when i needed to skip 100000 lines in my file it took about a second in opposite to 22 seconds with getline.