My JeKyll Tips with Github Pages

5 years of using Jekyll with Github Pages

This is the page where I will put all my tips and tricks for Jekyll and Github Pages.

What is Jekyll and Github Pages ?

Jekyll is a static site generator written in Ruby. It is the engine behind Github Pages. I’ve been using it for 5 years now, and I’m very happy with it.

Running Jekyll locally

Nowadays, it is possible to run Jekyll locally on Windows, Linux and Mac, using Docker. Altough I have used Jekyll native on Linux for years, I now prefer to use Docker, because it is easier to install and maintain.

Pre-requisites: Docker must be installed on your system.

If you have a repository with some github pages, you can run Jekyll locally with the following command:

$ docker run -it --rm -v .:/usr/src/app -p "4000:4000" starefossen/github-pages

The docker image “starefossen/github-pages” is a pre-built image with Jekyll and Github Pages GEM installed. It means that you can run Jekyll locally, with the same version of Jekyll and Github Pages as Github without any further installation.

The previous command will run Jekyll in the current directory, and will serve the site on port 4000. You can then browse your site at http://localhost:4000.

Redirecting some pages

When I migrated some pages to new URLs, I wanted to redirect the old URLs to the new ones. The reason is that some other websites or forum posts could have links to the old URLs, and I wanted to keep them working.

So the trick is very easy because Github Pages supports the HTTP 301 redirections with the installed GEM called jekyll-redirect-from.

Simply activate the GEM in your _config.yml file:

  - jekyll-redirect-from

Then, in your page, add the following YAML front matter:

layout: post
title: My JeKyll Tips with Github Pages
  - /old-url-1
  - /old-url-2

My post goes here.

Adding asciinema player

I like to add asciinema player to my posts, to show some terminal sessions.

First I need to record a terminal session with asciinema:

$ asciinema rec my-session.cast

First, import this JavaScript at the end of the <body> tag:

 <script src="/asciinema/asciinema-player.js"></script>  

At the top of the page, I can add the following CSS to style the player:

  <link rel="stylesheet" type="text/css" href="/asciinema/asciinema-player.css">

Then I can add the player to my post:

<asciinema-player src="/asciinema/my-session.cast" cols="80" rows="24"></asciinema-player>

or create a tag for Jekyll :

<asciinema-player src="" idle-time-limit="2"></asciinema-player>

This tag can be called like this:

<asciinema-player src="asciinema/my-session.cast" idle-time-limit="2"></asciinema-player>

Here is an example of a page with an asciinema player.

Adding Mermaid diagrams

This is an example of mermaid diagram:

flowchart TD; A[Deploy to production] --> B{Is it Friday?}; B -- Yes --> C[Do not deploy!]; B -- No --> D[Run]; C --> E[Enjoy your weekend!]; D --> E;

Don’t be fooled, this is a generated diagram from a text description. This is not a picture.

Here is the related text description of this diagram.

flowchart TD;
    A[Deploy to production] --> B{Is it Friday?};
    B -- Yes --> C[Do not deploy!];
    B -- No --> D[Run];
    C --> E[Enjoy your weekend!];
    D --> E;

The following steps show how to setup mermaid on your Jekyll site.

Note: This tip does not need a Jekyll plugin.

Creating an include file

First create a file named mermaid.html in the _includes directory.

<script type="module">
    import mermaid from '';

This loads JQuery and Mermaid, and then initialize Mermaid on the page. It parses all the <div> with the class mermaid and renders the diagrams.

In the footer of your page before the end of the BODY tag, add the following include:

{% if page.mermaid }
  {% if page.mermaid }
  {% include mermaid.html %}
{% endif %}

Adding a parameter to the front-matter

Then simply add the parameter mermaid: true to the front-matter of your page, if the page or the post contains mermaid diagrams to be displayed.

Here is the example related to this page.

layout: post
title: My JeKyll Tips with Github Pages
subtitle: 5 years of using Jekyll with Github Pages
logo: jekyll-logo.png
category: articles
tags: [Site, Jekyll]
lang: en
ref: my-jekyll-tips-with-github-pages
permalink: /my-jekyll-tips-with-github-pages/
mermaid: true

Adding a mermaid diagram

Then, in your content, use the following syntax, wrapping a diagram into a DIV with the class mermaid :

<div class="mermaid">
flowchart TD;
    A[Deploy to production] --> B{Is it Friday?};
    B -- Yes --> C[Do not deploy!];
    B -- No --> D[Run];
    C --> E[Enjoy your weekend!];
    D --> E;

Inside the DIV, simply use the mermaid syntax.

One last pretty mermaid diagram

This is a mindmap created by mermaid. This is so cool.

mindmap root((Learning Java)) Books Algorithms Clean Code Java 8 in Action Frameworks Spring Framework Quarkus Framework IDE Eclipse IntelliJ NetBeans VisualCode Build Tools Maven Gradle


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