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Screen Scraping With Ruby

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Scripting languages are the bomb. I pretty much live in them right now.

Ruby is my current (and probably will be for a long time) favourite scripting language, and it has a library for everything. Even if there isn't a library for what you want, it's super easy to write your own.

I ran into a problem a while back that ruby solved nicely for me. I was downloading wallpapers from a website, but it was getting annoying. Really, I just wanted to grab them all, but of course didn't want to spend the time doing it myself. With 4GB+ of hi resolution wallpapers to download it would have taken me forever to download them all by hand.

So instead I wrote a little script to do it, and let it run.

I'm not going to post the entire script verbatim, since it's old code now, doesn't work anymore (the site is sort of gone), but I'll explain and post relevant bits

First, there is a main page which lists all the other pages (thankfully), so I can grab that page and get the main list of things to download. They are all the links that match a certain regex:

It's been a while since I wrote the code, but I uniq'd and flatten'd the main_links array too. Can't remember why.

There are also multiple pages per item, if that makes sense. The main page would have links for Foo, Bar, and Baz, but then there might be foo-2.htm, foo-3.htm, etc. These aren't linked nicely, so I just sort of iterated up to 20 and checked to see if the page was there, and added those too:

I had to check for the unavailability of the page that way, since they did it weird, doing a redirect and then showing a 404 page, but never giving a 404 response code. Weird.

I also threw a sleep in there, to be a little nice.

Now the fun part starts. They had a Javascript function 'protecting' the links. In order to open the page, a Javascript function 'decoded' something which made the link, and then this link would be the URL of the page holding the high-res image. It was easy to rewrite said function in ruby.

Now I was ready to process things more thoroughly:

Iterate through, find the links I want, pull out the relevant 'code' and decode it, visit that link, find the image I want, then download it.

A little while later, I've got a ton of images for desktop goodness. Ruby Win.


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