gistfile1.rb

#!/usr/bin/env ruby
# -*- ruby -*-

block = ["news.ycombinator.com",
         "reddit.com",
         "stackoverflow.com"]

fblock = block.map{|e|"127.0.0.1 #{e}"}.join("\n")

hosts = File.readlines("/etc/hosts").join

if ARGV[0] == "stop"
  if hosts =~ /# BEGIN INTERBLOCK BLOCK/
    hosts.sub!(/\n# BEGIN INTERBLOCK BLOCK\n.*\n# END INTERBLOCK BLOCK\n/m,'')
  end
else # start
  if hosts =~ /# BEGIN INTERBLOCK BLOCK/
    puts "already started!"
  else
    hosts << "\n# BEGIN INTERBLOCK BLOCK\n#{fblock}\n# END INTERBLOCK BLOCK\n"
  end
end

File.open("/etc/hosts","w") do |f|
  f.puts hosts
end