Ruby script to invalidate objects on Amazon's CloudFront CDN (shows status of recent requests also)

## aws_cf_invalidate.rb
require 'rubygems'
require 'hmac-sha1' # on OS X: sudo gem install ruby-hmac
require 'net/https'
require 'base64'

#
# CHANGE ME: S3 access credentials go here, along with CloudFront Distribution ID
#
s3_access=''
s3_secret=''
cf_distribution=''

paths = nil

if ARGV[0] =~ /\-help/
  puts "usage: aws_cf_invalidate.rb [file1.html dir1/file2.jpg ...]"
  puts "File list is optional... not specifying a list will return current status of recent invalidation requests"
  exit
end

if ARGV.length > 0
  paths = '<Path>/' + ARGV.join('</Path><Path>/') + '</Path>'
end

date = Time.now.utc
date = date.strftime("%a, %d %b %Y %H:%M:%S %Z")
digest = HMAC::SHA1.new(s3_secret)
digest << date

uri = URI.parse('https://cloudfront.amazonaws.com/2010-08-01/distribution/' + cf_distribution + '/invalidation')

if paths != nil
  req = Net::HTTP::Post.new(uri.path)
else
  req = Net::HTTP::Get.new(uri.path)
end

req.initialize_http_header({
  'x-amz-date' => date,
  'Content-Type' => 'text/xml',
  'Authorization' => "AWS %s:%s" % [s3_access, Base64.encode64(digest.digest)]
})

if paths != nil
  req.body = "<InvalidationBatch>" + paths + "<CallerReference>ref_#{Time.now.utc.to_i}</CallerReference></InvalidationBatch>"
end

http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
http.verify_mode = OpenSSL::SSL::VERIFY_NONE
res = http.request(req)

# TODO: Check status code and pretty print the output
# Tip: pipe the output to | xmllint -format - |less for easier reading
#puts $STDERR res.code
puts res.body