Download all xkcd comics.

README.md

$ git clone https://gist.github.com/ryanmjacobs/50a7944e929c1329ad44 xkcd
$ cd xkcd
$ gem install colorize
$ chmod +x xkcd.rb
$ ./xkcd.rb

Some extra info if you're curious:

• git clone ... xkcd grabs these files and puts them in a directory called xkcd.
• cd xkcd goes into that directory.
• gem install ... installs a Ruby gem. Ruby gems are small libraries and you can find one for pretty much anything.
• chmod +x xkcd.rb makes the file xkcd.rb executable. Notice that the file turns green after you do it.
• ./xkcd.rb executes the file. Pretty simple.

xkcd.rb

#!/usr/bin/env ruby
# dl all xkcd

require "json"
require "colorize"
require "open-uri"

Dir.mkdir "xkcd" if not Dir.exists?("xkcd")

$all_json = []
current_num = JSON.parse(open("http://xkcd.com/info.0.json").read)["num"].to_i

def quit!
    File.open("xkcd/info.json", "w") { |f| f.write(JSON.pretty_generate($all_json)) }
end

def error(string)
    puts "error: #{string}".red
    File.open("xkcd.log", "a") { |f| f.write("#{Time.now.strftime("%F %T")} ERROR: #{string}\n") }
end

trap "SIGINT" do
    quit!
    exit 1
end

(1..current_num).each do |i|
    begin
        json    = JSON.parse(open("http://xkcd.com/#{i}/info.0.json").read)
        str_num = i.to_s.rjust(3, "0")
        fname   = "##{str_num} - #{json["safe_title"]}.png"

        # make filename safe
        fname.gsub!("/", "\u2215") # unicode slash

        puts fname
        $all_json << json

        # numbers mismatch!
        if i != json["num"].to_i then
            abort "error: numbers mismatch! #{i} != #{json["num"].to_i}"
        end

        # skip if already downloaded
        next if File.exists?("xkcd/#{fname}")

        # write new image
        File.open("xkcd/#{fname}", "wb") do |local|
            open("#{json["img"]}", "rb") do |remote|
                local.write(remote.read)
            end
        end
    rescue Errno::ECONNRESET
        error "##{str_num} - connection reset. skipping"
    rescue OpenURI::HTTPError
        error "##{str_num} - 404 not found. skipping"
    end
end