A timesaving subdomain rake task

A time saving rake task for adding or updating your local /etc/hosts file. I created this for Bugle, allowing me to quickly configure my development machine hosts file with subdomains used in the app. See the inline comments for an explanation.

Has the added feature of an array of default hosts to always add when you run it. Work is done on a tmp file then, then sudo copied on top of /etc/hosts. It exists as a gist on github so i’ll be sure to post any updates to it there.

# subdomains.rake (in /lib/tasks)
namespace :subdomains do

  desc "adds the necessary hosts to your /etc/hosts file from current subdomains in your application"
  task :setup => :environment do
    # NOTE: default_hosts is used as a locator for the line to update in /etc/hosts
    tmp_file, changed = '/tmp/etc_hosts_copy', false
    default_hosts, hosts    = %w(blog.local emptyblog.blog.local), []

    # find all the subdomains used in your app (push to hosts array) - modify this to suit your app
    Blog.find(:all).each { |blog| hosts << "#{blog.subdomain}.blog.local" unless blog.subdomain.blank? }
    
    # build hosts line to add/edit
    host_line = "127.0.0.1 " + hosts.sort.unshift(default_hosts).join(' ')

    # work with a copied hosts file in tmp
    %x[cp /etc/hosts #{tmp_file}]

    file = File.new(tmp_file)
    lines = file.readlines
    lines.each do |line|
      changed = true if line.gsub!(/^127.0.0.1 #{Regexp.escape(default_hosts.join(' '))}.+$/, host_line)
    end

    # add line, if no line found for update
    lines += ["\n", host_line, "\n"] unless changed
    file = File.new(tmp_file,'w')
    lines.each { |line| file.write(line) }
    file.close

    # copy hosts file from tmp - may ask for sudo password
    %x[sudo -p "Password:" cp #{tmp_file} /etc/hosts]
    
    # explain what happened
    puts "\nAdded the following domains:"
    hosts.each { |host| puts "* http://#{host}" }
    puts "\nAlso added defaults:"
    default_hosts.each { |default| puts "* http://#{default}" }
    puts "\n"
  end
end

To run simply type

rake subdomains:setup