How to Scrape an Entire Wordpress Blog
7
2008
When I find a new blog that I really like or think has some good information I usually want to read the whole thing, and in the past, I've been frustrated by how annoying it is to do it online. I just want all posts in one document, free of ads, that I can read from start to finish.
I've also been having the itch to learn the Perl programming language, and I thought this would be a good project to get my feet wet.
Strategy
Since the majority of blogs I read are in written in WordPress, it's pretty easy to take advantage of the GET string that can be used to access each post. The GET string looks like http://www.devtrench.com/?p=2. Normally, post id's start with 1 and auto increment from there, so all we have to do is figure out what the id is of the latest post, and write some code that will loop over a scraper that many times. Sometimes the latest post id will be hidden in the HTML of the post somewhere, and other times you just have to guess at it for a while until you figure it out.
Code
Here's the Perl code that I'm currently using to do this. It's meant to be run from the command line, and I output the data to a file using '> output.txt' after the command. Also, I ripped off most of this code from PLEAC-Perl, which is an online Perl cookbook. Cookbooks can really accelerate learning a language when you want to do specific tasks like this.
Hopefully this code is commented enough for you to understand what is going on.
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#!/usr/bin/perl -w
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# http://www.devtrench.com - How to Scrape a Wordpress Blog
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# These packages are required so load them
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use LWP::UserAgent;
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use HTTP::Request;
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use HTTP::Response;
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use URI::Heuristic;
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# Usage: perl fetch_blog.pl http://www.domain.com highest_post_id start_pattern end_pattern
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my $start_pattern = shift; # a start pattern to match. we don't want the entire page so find some unique text before the blog post. it's best to put the pattern in single quotes
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my $url = URI::Heuristic::uf_urlstr($raw_url);
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$| = 1; #to flush next line
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# fire up a new user agent that can browse the web for us
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my $ua = LWP::UserAgent->new();
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$ua->agent("DEVTRENCH.COM WordPress Post Fetcher v0.1"); # give it time, it'll get there
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# now loop through all posts
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for ($i=1;$i<=$post_num;$i++) {
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# here we request each post from the site using the get string common to wordpress blogs
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my $req = HTTP::Request->new(GET => $url.'/?p='.$i);
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$req->referer("http://www.devtrench.com"); # perplex the log analysers
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my $response = $ua->request($req);
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if ($response->is_error())
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{
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# uh oh there was an error, probably a 404 which is caused by deleted or non published posts
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} else {
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my $content;
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$content = $response->content();
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my $test;
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$_ = $content;
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# this is the regular expression that will match the start and end pattern
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$content = $1;
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}
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# this line prints out what the regex found as html, but it could easily be modified to print as plain text as well
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}
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}
This was a fun experiment for me and a great way to finally get around to learning Perl. I always find that if I create small tasks like this for myself that learning a language or framework is much more interesting and rewarding. Now if you want to do this in PHP, which is what I usually program in, you can follow the same logic using curl as your user agent.
Hint 1: If you use this code as is it will print out HTML. Surround the HTML that it generates with basic <html> and <body> tags and create your own styles in the <head>. Then you can view it in a web browser and print to PDF.
Hint 2: The blog I was trying to scrape did not allow me to hotlink images from my HTML file, but saving the page as HTML from FireFox was a workaround for that, and then I saved that created page as a PDF.
4 Comments » 3,821 views
Posted in: Programming, WordPress
Comment by Scott (spammer) Fish
on 11 Jul 2008 at 12:35 pm #
This is a really cool way to scrape. Thanks for the code!
Comment by Link Building Bible
on 19 Jul 2008 at 10:08 am #
Yah, this is a great idea….. i have that same problem… i find a new blog i wanna read about, and then I hate trying to navigate through it all…
Comment by Mike Wanner
on 19 Apr 2009 at 5:48 pm #
I have a quick question that maybe related – I am looking for a program that can pull all the COMMENTS from posts. For example, on a site that is similiar to mine I want to grab all the people who are posting and put it into a format or list. Many people post and put their full information and URL/URI. This was I can build a list quickly. Any ideas?
Comment by James Ehly
on 19 Apr 2009 at 8:15 pm #
My PERL skills are still pretty green
In PHP you’d use preg_match_all on a pattern that would find a single comment. That would find all the comments and store them in an array for further processing. You’ll need to find a PERL guru or try a Google search to find something that might work with this script.
If anyone else that knows PERL would like to make a suggestion for this, that would be great!