Sort a list of hostnames so that www. versions show up next to non-www. versions of the same domain

sort-domains.rb

#!/usr/bin/env ruby
#
# Sometimes you want to sort a list of hostnames/domains and want
# example.com to sort next to www.example.com. This does that.
#
# Author: Rob Miller <r@robm.me.uk>
#
# Usage:
#
#   $ cat foo.txt | sort-domains
#
#   $ sort-domains foo.txt
#
# Assumes each line of input is a hostname.

ARGF.read.lines.sort_by { |u| u.sub(/^www\./, "") }.each { |u| puts u }