Getting the nth line of a text file in C++

Question

I need to read the nth line of a text file (e.g. textfile.findline(0) would find the first line of the text file loaded with ifstream textfile). Is this possible? I don't need to put the contents of the file in an array/vector, I need to just assign a specific line of the text file to a varible (specifically a int).

P.S. I am looking for the simplest solution that would not require me to use any big external library (e.g. Boost) Thanks in advance.

Answer 1

If you want to read the start of the nth line, you can use stdin::ignore to skip over the first n-1 lines, then read from the next line to assign to the variable.

template<typename T>
void readNthLine(istream& in, int n, T& value) {
  for (int i = 0; i < n-1; ++i) {
    in.ignore(numeric_limits<streamsize>::max(), '\n');
  }
  in >> value;
}

Answer 2

It's certainly possible. There are (n-1) '\n' characters preceding the nth line. Read lines until you reach the one you're looking for. You can do this on the fly without storing anything except the current line being considered.