diff --git a/bin/wayback_machine_downloader b/bin/wayback_machine_downloader
index 64ace86..c4ef13f 100755
--- a/bin/wayback_machine_downloader
+++ b/bin/wayback_machine_downloader
@@ -2,6 +2,7 @@
 
 require_relative '../lib/wayback_machine_downloader'
 require 'optparse'
+require 'pp'
 
 options = {}
 option_parser = OptionParser.new do |opts|
@@ -11,19 +12,26 @@ option_parser = OptionParser.new do |opts|
   opts.separator "Download any website from the Wayback Machine."
 
   opts.separator ""
-  opts.separator "Optional option:"
+  opts.separator "Optional options:"
 
   opts.on("-t", "--timestamp TIMESTAMP", Integer, "Only files on or before timestamp supplied (ie. 20150806225358)") do |t|
     options[:timestamp] = t
   end
 
+  opts.on("--accept-regex [ACCEPT_REGEX]", String,"Specify a regular expression to download. If a path doesn't meet this regex, it won't get downloaded.") do |accept_regex|
+    options[:accept_regex] = accept_regex
+  end
+
   opts.on("-v", "--version", "Display version") do |t|
     options[:version] = t
   end
 end.parse!
 
-if base_url = ARGV[0]
-  wayback_machine_downloader = WaybackMachineDownloader.new base_url: base_url, timestamp: options[:timestamp]
+# this used to be 0. we want to look at the /last/ option.
+# 
+# TODO: this argument needs to be handled better. argument handling is sorta messy.
+if base_url = ARGV[-1]
+  wayback_machine_downloader = WaybackMachineDownloader.new base_url: base_url, timestamp: options[:timestamp], accept_regex: options[:accept_regex]
   wayback_machine_downloader.download_files
 elsif options[:version]
   puts WaybackMachineDownloader::VERSION
diff --git a/lib/wayback_machine_downloader.rb b/lib/wayback_machine_downloader.rb
index b33dfa5..a92b1af 100644
--- a/lib/wayback_machine_downloader.rb
+++ b/lib/wayback_machine_downloader.rb
@@ -13,6 +13,7 @@ class WaybackMachineDownloader
   def initialize params
     @base_url = params[:base_url]
     @timestamp = params[:timestamp].to_i
+    @accept_regex = /#{params[:accept_regex]}/
   end
 
   def backup_name
@@ -48,7 +49,21 @@ class WaybackMachineDownloader
         end
       end
     end
-    file_list_curated
+
+    # if accept_regex not defined, just return the file_list_curated
+    if @accept_regex.nil?
+      return file_list_curated
+    end
+
+
+    # accept_regex defined. now we need to create a filtered list.
+    filtered_file_list_curated = Hash.new
+    file_list_curated.each do |file_id, fileinfo|
+      if fileinfo[:file_url].match @accept_regex
+        filtered_file_list_curated[file_id] = fileinfo
+      end
+    end
+    return filtered_file_list_curated
   end
 
   def get_file_list_by_timestamp
@@ -64,6 +79,10 @@ class WaybackMachineDownloader
     puts "Downloading #{@base_url} to #{backup_path} from Wayback Machine..."
     puts
     file_list_by_timestamp = get_file_list_by_timestamp
+    if file_list_by_timestamp.count == 0
+      puts "No files to download. Possible reasons:\n\t* Accept regex didn't let any files through (Accept Regex: \"#{@accept_regex.to_s}\")\n\t* Site is not in wayback machine."
+      return
+    end
     count = 0
     file_list_by_timestamp.each do |file_remote_info|
       count += 1
diff --git a/test/test_wayback_machine_downloader.rb b/test/test_wayback_machine_downloader.rb
index 5299487..79479e2 100644
--- a/test/test_wayback_machine_downloader.rb
+++ b/test/test_wayback_machine_downloader.rb
@@ -30,6 +30,16 @@ class WaybackMachineDownloaderTest < Minitest::Test
     assert_equal file_expected, @wayback_machine_downloader.get_file_list_by_timestamp[-1]
   end
 
+  def test_file_list_notthere_regex
+    regextester = WaybackMachineDownloader.new base_url: 'http://www.onlyfreegames.net', accept_regex: 'abc123'
+    assert_equal 0, regextester.get_file_list_curated.length
+  end
+
+  def test_file_list_singleresult_regex
+    regextester = WaybackMachineDownloader.new base_url: 'http://www.onlyfreegames.net', accept_regex: 'menu.html$'
+    assert_equal 1, regextester.get_file_list_curated.length
+  end
+
   def test_file_download
     @wayback_machine_downloader.download_files
     linux_page = open 'websites/www.onlyfreegames.net/linux.htm'