Question

I often see a spinning animation in the command prompt/shell consisting of -, /, and \. This type of printing, which simply overwrites whatever is already there, is also used to show progress in downloading stuff with command line applications.
How is this done?

Answer 1

Usually this is done by printing a backspace character (ASCII code 8) and then the next character in the sequence. In most programming languages you can just use \b in a string for this.

For example, here is some Python code for this:

import time
import sys
sys.stdout.write(' ')
while True:
    for c in ('/', '-', '\\', '|'):
        time.sleep(1)
        sys.stdout.write('\b' + c)
        sys.stdout.flush()