Deleting multiple lines of terminal output using ruby

Question

I would like to be able to output two lines to the terminal and then delete both of them. I know you can do one by doing something like

print "\b"*whatever

but I would like to do something more like this:

[1, 2, 3, 4, 5].each do |item|
    # code to delete the previous two lines
    print item.to_s + "\nHello!"
end

The output would quickly go through all of the following

1
Hello!
2
Hello!
3
Hello!
4
Hello!
5
Hello!

but by the end, the final iteration would be all you see.

Answer 1

Well, for simple things, if you can assume an ANSI-compatible terminal (usually a good bet), you can just directly output ANSI codes. For instance,

 5.times do |item|
    print "\r" + ("\e[A\e[K"*3) if item > 0
    puts "#{item+1}\nHello!"
 end

Where \r moves the cursor to the start of the line, \e[A moves the cursor up one line, and \e[K clears from the cursor position to the end of the line. If you don't need anything further down the screen, you can also just send \e[J once you have the cursor where you want; that clears all the way to the end of the screen.

For more sophisticated stuff, you could start by taking a look at the Highline gem.