How to animate the command line?

Question

I have always wondered how people update a previous line in a command line. a great example of this is when using the wget command in linux. It creates an ASCII loading bar

Answer 1

There are two ways I know of to do this:

• Use the backspace escape character ('\b') to erase your line
• Use the curses package, if your programming language of choice has bindings for it.

And a Google revealed ANSI Escape Codes, which appear to be a good way. For reference, here is a function in C++ to do this:

void DrawProgressBar(int len, double percent) {
  cout << "\x1B[2K"; // Erase the entire current line.
  cout << "\x1B[0E"; // Move to the beginning of the current line.
  string progress;
  for (int i = 0; i < len; ++i) {
    if (i < static_cast(len * percent)) {
      progress += "=";
    } else {
      progress += " ";
    }
  }
  cout << "[" << progress << "] " << (static_cast(100 * percent)) << "%";
  flush(cout); // Required.
}