![]() This indicates that the files are gzip compressed, and that we’ll therefore need to decompress them before accessing their contents.īefore we get to that, let’s first extract this second round of sitemap URLs. They just list more sitemaps, and ones with a. We can see here that these initial sitemaps don’t actually list pages on the site. If we clean this up manually, it looks more like this. I guess there’s no inbetween with Google. Newlines with carriage returns, or nothing. We’re instead left with a mess of XML that’s a bit dense to parse by eye. The content of these sitemap files don’t include any additional character returns they don’t even include new lines. If we use sed again to eliminate the \r carriage returns before passing them as arguments to curl, then we’ll be able to actually download and print the sitemap files. I can only assume that this is because Google is running MS DOS on their servers, but, in any case, the carriage returns don’t play nicely with Unix utilities. The reason that we get this error is that Google isn’t just using \n to indicate a new line in their sitemap files they’re using \n for a new line and \r as a carriage return. curl: (3) Illegal characters found in URLĬurl: (3) Illegal characters found in URL The only problem is that when we do this, we end up with a somewhat cryptic error from curl. The -n1 argument to xargs here simply tells it to execute curl separately for each URL that’s piped in. We can then pipe these URLs into xargs to run curl again with each URL passed as an argument. Running this command will print out the list of sitemaps that we’ll want to download and nothing else. We’ll then use \1 to replace the entire line with the contents of this first matched group, and use sed’s p command to print out the replacement. * inside of the parenthesis grabs all of the text where we expect the sitemap URL to be, and the parenthesis themselves specify that this is a matching group. ![]() We’ll use sed’s -n argument to suppress printing out each line automatically, and then check for a pattern of ^Sitemap: (.*)$ to find the sitemap URLs. We can pipe the full output of the robots.txt file through sed in order to extract these initial sitemap URLs. ![]() ![]() There’s a bunch of boring stuff that get printed out when you run this command, but the interesting part is the list of sitemaps. We use the -N option here to disable buffering so that the entire file gets output at once. We’ll use curl here to download the file and print out its contents to the terminal. The first step towards extracting a list of URLs from a site is to parse its robots.txt file where the sitemap(s) will be listed. OK, maybe “simple” is pushing it a little bit, but it’s really not that bad when you break it down step by step.Īnd that’s exactly what we’ll do here: break this chain of piped commands up into easily understandable steps. Still, even the Google Play sitemap can be parsed with a simple bash “one-liner.” curl -N | That site has a lot of pages, and it has a particularly complex sitemap structure that involves both nested and compressed sitemaps. Let’s take the sitemap for Google Play as an example. In fact, you can generally parse them and extract them using standard command-line utilities without any need for specialized tools. Things can get slightly more complicated when sitemaps index additional sitemaps, or when they’re explictly compressed using gzip, but they’re overall fairly straightforward to deal with. Sitemaps are basically just XML files which enumerate the pages available to scrape on a website, and they’re generally quite simple. These are extremely useful once you’re at the stage of actually scraping a website, but it can also sometimes be useful to quickly parse a site’s sitemap to get an idea of the size of the website and the scope of the scraping endeavor at hand. Most web scraping libraries provide built-in mechanisms for parsing sitemaps and processing the listed pages.įor example, Scrapy includes a generic SitemapSpider for this purpose, and simplecrawler automatically discovers resources from sitemaps. Sites which provide sitemaps are quite literally asking to be scraped it’s a direct indication that the site operators intend for bots to visit the pages listed in the sitemaps. It’s certainly possible to scrape sites by crawling those links, but things become much easier with a sitemap that lays out a site’s content in clear and simple terms. Without a sitemap, a website is just a labyrinthian web of links between pages. A wise man once said that sitemaps are the window into a website’s soul, and I’m not inclined to disagree.
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