How do command line tools change their output after outputting it?

Question

I\'ve noticed that a lot of command line tools, wget for example, will show progress as a number or progress bar that advances as a process is completed. While the question isn\

Answer 1

I can only speak about node.js, but the built-in readline module has some very basic screen handling functionality built-in. For example:

var readline = require('readline');
var c = 0;
var intvl = setInterval(function() {
  // Clear entirety of current line
  readline.clearLine(process.stdout, 0);
  readline.cursorTo(process.stdout, 0);
  process.stdout.write('Progress: ' + (++c) + '%');
  if (c === 100)
    clearInterval(intvl);
}, 500);

There are also third party modules if you want to get fancier, such as multimeter/meterbox and blessed/blessed-contrib.

Generally speaking though, some programs use ncurses, while others simply just manually output the ANSI escape codes to clear and redraw the current line.