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

Here is the answer for your question... (python)

def disp_status(timelapse, timeout):
  if timelapse and timeout:
     percent = 100 * (float(timelapse)/float(timeout))
     sys.stdout.write("progress : ["+"*"*int(percent)+" "*(100-int(percent-1))+"]"+str(percent)+" %")
     sys.stdout.flush()
     stdout.write("\r  \r")

Answer 2

One way to do this is to repeatedly update the line of text with the current progress. For example:

def status(percent):
    sys.stdout.write("%3d%%\r" % percent)
    sys.stdout.flush()

Note that I used sys.stdout.write instead of print (this is Python) because print automatically prints "\r\n" (carriage-return new-line) at the end of each line. I just want the carriage-return which returns the cursor to the start of the line. Also, the flush() is necessary because by default, sys.stdout only flushes its output after a newline (or after its buffer gets full).