Question

I have a relatively simple question. Say I have a file but I only want to access line X of the file until line Y, whats the easiest way of doing that?

I know I can read in the lines one by one keeping count, until I reach the lines that I actually need, but is there a better more elegant solution?

Thanks.

Answer 1

In C++, no, not really (well, not in any language I’m familiar with, really).

You have to start at the start of the file so you can figure where line X starts (unless it’s a fixed-record-length file but that’s unlikely for text).

Similarly, you have to do that until you find the last line you’re interested in.

You can read characters instead of lines if you’re scared of buffer overflow exploits, or you can read in fixed-size block and count the newlines for speed but it all boils down to reading and checking every character (by your code explicitly or the language libraries implicitly) to count the newlines.