List the files in a BitTorrent torrent with this quick Ruby script. Requires that you gem install bencode awesome_print before you run it.

#!/usr/bin/env ruby
#
# torrentdump - prints the contents of a torrent.
#
# Copyright (C) 2011 Paul Legato. All rights reserved.
# Licensed for personal, non-commercial use only.
# This code comes with NO WARRANTY, express or implied.
#
# Prerequisite gem setup:
#   sudo gem install bencode awesome_print
#

require 'rubygems'
require 'bencode'
require 'awesome_print'

unless ARGV[0]
  STDERR.puts <<END

Usage: torrentdump <filename> <-v>

If -v is given, prints the entire contents of the torrent except the binary "pieces" hash data.

If -vv is given, prints everything, including the binary hash data.

Otherwise, prints only the file list.

END
  exit 1
end

# Method from http://stackoverflow.com/questions/3201890/is-there-an-elegant-way-to-remove-a-specific-key-from-a-hash-and-its-sub-hashes
def recursive_delete!(hash, to_remove)
  hash.delete(to_remove)
  hash.each_value do |value|
    recursive_delete!(value, to_remove) if value.is_a? Hash
  end
end

data = BEncode.load(File.read(ARGV[0]).force_encoding("binary"))

if ARGV[1] == "-vv"
  ap data
elsif ARGV[1] == "-v"
  recursive_delete!(data, "pieces")
  ap data
else
  if data["info"]["files"]
    dir = data["info"]["name"] || ""
    ap data["info"]["files"].map {|x| dir + "/" + x["path"].join("/") }  
  else
    ap data["info"]["name"]
  end
end

A quick example:

% torrentdump ubuntu-10.04.2-server-i386.iso.torrent 
"ubuntu-10.04.2-server-i386.iso"

Torrent dissection: of interest here..

• Ruby 1.9 imposes a character encoding on every string by default. This is fine for dealing with text, but caused errors in the BEncode library. (For some reason, the authors of BitTorrent chose to re-invent the wheel and developed their own binary encoding format.) We use the #force_encoding method on the torrent data to make Ruby treat the data as raw binary data and not try to interpret it.
• More than you ever wanted to know about what’s inside a .torrent file

The Torrentdump source code is available on GitHub.

Stop calling your tests “stories.” Really.

They’re not “stories”. They’re tests. They don’t tuck you into bed with a glass of warm milk and a nice fairytale to dream about; they assert that certain things should happen and complain when they don’t, in a purely mechanical and precise way. We’re programming computers, machines of pure logic here, not reading to children. Let’s dispense with the pointless cutesy façade and focus precisely on the task at hand.

They don’t deliver what they promise, anyway. Frameworks like RSpec and Cucumber do not let you write tests in “plain English”. They let you write tests in a horrible chimeric programming language that adopts a superficial English-like veneer over top of what’s essentially a regular old unit testing framework.

It winds up giving you the benefits of neither English nor a well written testing API; your code simply becomes excessively verbose for the sake of a (highly fake and brittle) natural language veneer. You’re still highly restricted in what you can say, just like a regular old programming language. The set of Englishisms that you can use is so grossly restricted and precisely defined that you can’t think in anything remotely like English. You have to memorize a precise set of rigid, fixed English labels and use that and only that. You do get the verbosity of natural language, though, along with the restricted semantic domain of the API. You get the benefits of neither and the disadvantages of both.

Since you’re memorizing a highly restricted API anyway, skip the twee cruft and just use a short and precise API from the start, without the pseudo-natural language clutter.