How do I pretty-print HTML with Nokogiri?

Question

I wrote a web crawler in Ruby and I'm using Nokogiri::HTML to parse the page. I need to print the page out and while messing around in IRB I noticed a pretty_print method. However it takes a parameter and I can't figure out what it wants.

My crawler is caching the HTML of the webpages and writing it to files on my local machine. I would like to "pretty print" the HTML so that it looks nice and properly formatted when I do so.

Answer 1

The answer by @mislav is somewhat wrong. Nokogiri does support pretty-printing if you:

• Parse the document as XML
• Instruct Nokogiri to ignore whitespace-only nodes ("blanks") during parsing
• Use to_xhtml or to_xml to specify pretty-printing parameters

In action:

html = '<section> <h1>Main Section 1</h1><p>Intro</p> <section> <h2>Subhead 1.1</h2><p>Meat</p><p>MOAR MEAT</p> </section><section> <h2>Subhead 1.2</h2><p>Meat</p> </section></section>'  require 'nokogiri' doc = Nokogiri::XML(html,&:noblanks) puts doc #=> <section> #=>   <h1>Main Section 1</h1> #=>   <p>Intro</p> #=>   <section> #=>     <h2>Subhead 1.1</h2> #=>     <p>Meat</p> #=>     <p>MOAR MEAT</p> #=>   </section> #=>   <section> #=>     <h2>Subhead 1.2</h2> #=>     <p>Meat</p> #=>   </section> #=> </section>  puts doc.to_xhtml( indent:3, indent_text:"." ) #=> <section> #=> ...<h1>Main Section 1</h1> #=> ...<p>Intro</p> #=> ...<section> #=> ......<h2>Subhead 1.1</h2> #=> ......<p>Meat</p> #=> ......<p>MOAR MEAT</p> #=> ...</section> #=> ...<section> #=> ......<h2>Subhead 1.2</h2> #=> ......<p>Meat</p> #=> ...</section> #=> </section> 

Answer 2

By "pretty printing" of HTML page I presume you meant that you want to reformat the HTML structure with proper indentation. Nokogiri doesn't support this; the pretty_print method is for the "pp" library and the output is useful for debugging only.

There are several projects that understand HTML well enough to be able to reformat it without destroying whitespace that is actually significant (the famous one is HTML Tidy), but by Googling I've found this post titled "Pretty printing XHTML with Nokogiri and XSLT".

It comes down to this:

xsl = Nokogiri::XSLT(File.open("pretty_print.xsl")) html = Nokogiri(File.open("source.html")) puts xsl.apply_to(html).to_s 

It requires you, of course, to download the linked XSL file to your filesystem. I've tried it very quickly on my machine and it works like a charm.