I’ve had a project going on for a month or so to re-do a Confluence wiki into Markdown files, hence why I pusblished The Markdown Cheatsheet, and Jekyll categories based menu.
One thing that can be handy in a wiki is “back links” i.e. what other pages link to this page.

The Requirements

I want to automatically find, and display, all other pages in a Jekyll site that link to the existing page.

Ruby Plugin

Ok, so let’s just skip straight to the meaty bit 😂

In your Jekyll root directory, if you don’t already have a folder called _plugins then create one.

mkdir _plugins

Let’s create a file called _plugins/backlinks_generator.rb

class BackLinksGenerator < Jekyll::Generator
  def generate(site)

    all_notes = site.collections['docs'].docs
    all_posts = site.posts.docs
    all_pages = site.pages

    all_docs = all_notes + all_posts + all_pages 

    # Identify backlinks and add them to each doc
    all_docs.each do |current_note|
      notes_linking_to_current_note = all_docs.filter do |e|
        e.content.include?(current_note.url)
      end
      current_note.data['backlinks'] = notes_linking_to_current_note
    end

  end

end

Here’s a brief run down of what the Ruby script does:

  • Creates 3 arrays: all_notes (i.e. a collection), all_post, all_pages.
  • Concatinates the 3 arrays into one larger array called all_docs.
  • In the current page that Jekyll is processing, loop through the all_docs array and find out if there is a link to the current page.
  • Store the found results in the page/post.data as an array called backlinks ( i.e. page.backlinks or post.backlinks)

Some CSS

Yeah, just so things look nice 😝

.backlink-box {
        background-color: #fffdf7;
        
}
.backlink-box:before {
        content: "What links here";
            font-style: italic;
            
}
.backlink-box li {
        line-height: 1em;
        
}

The Jekyll layout

I learned quickly that everything seems to link to the home page (i.e. “/”).
So while writing a section in my layout I had to include an exclusion (i.e. {% if page.url != home.url %} )

Now each page has an array of backlinks, or doesn’t.
I’ll check if backlinks exists, by checking if it is greater than 0 (zero), and if it is, I can just loop through it !

{% assign home = site.html_pages | where: 'url', '/' | first %}
{% if page.url != home.url %}
    {% if page.showbacklinks == true %}
        {% if page.backlinks.size > 0 %}
            <div class="backlink-box">
                <ul>
                {% for backlink in page.backlinks %}
                    <li><a href="{{ site.url }}{{ backlink.url }}">{{ backlink.title }}</a></li>
                {% endfor %}
                </ul>
            </div>
        {% endif %}
    {% endif %}
{% endif %}

Note:
You can disable showing the backlink on a per page / per post basis by using the front matter

showbacklinks: no

The Result

sweet screenshot goodness ….

what_links_here.png

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