Download and write .tar.gz files without corruption

Question

How do you download files, specifically .zip and .tar.gz, with Ruby and write them to the disk?

_{—
This question was originally specific to a bug in MacRuby, but the answers are relevant to the above general question.}

_{Using MacRuby, I've found that the file appears to be the same as the reference (in size), but the archives refuse to extract. What I'm attempting now is at: https://gist.github.com/arbales/8203385
Thanks!}

Answer 1

I've successfully downloaded and extracted GZip files with this code:

require 'open-uri'
require 'zlib'

open('tarball.tar', 'w') do |local_file|
  open('http://github.com/jashkenas/coffee-script/tarball/master/tarball.tar.gz') do |remote_file|
    local_file.write(Zlib::GzipReader.new(remote_file).read)
  end
end