Question

I have a Ruby script that outputs progress messages on the same line, using the carriage return character, like this:

print "\r#{file_name} processed."

As an example, the output changes from 'file001.html' processed. to 'file002.html.' processed and so on until the script completes.

I’d like to replace the last progress message with Done., but I can’t just write print "\rDone." because that piece of code outputs something like this:

Done.99.html processed.

I guess I have to empty the line after the last progress message and then print Done.. How do I do that?

Answer 1

You need to send the sequence of bytes that corresponds to the terminfo
variable clr_eol (capability name el) after using \r. There are several
ways that you could get that.

Simplest, assume that there’s a constant value. On the terminals I’ve checked
it is \e[K, but I’ve only checked a couple. On both of those the following
works:

clear = "\e[K"
print "foo 123"
print "\r#{clear}bar\n"

You could also get the value using:

clear = `tput el` 

Or you could use the terminfo gem:

require 'terminfo'
clear = TermInfo.control_string 'el'