title: How to rollback lines from cout?
body: <p>I'm coding a task monitoring, which updates tasks' progress using cout. I'd like to display one task progress per line, therefore I have to rollback several lines of the console.</p>
  
  <p>I insist on "several" because <code>\b</code> does the job for one line, but does not erase <code>\n</code> between lines.</p>
  
  <p>I tried <code>std::cout.seekp(std::cout.tellp() - str.length());</code> but <code>tellp()</code> returns -1 (failure).</p>