How to generate a list with links for each category when using hierarchical categories in Jekyll
Overview
One of the ways to structure content in a Jekyll environment is to put posts in subdirectories, where each subdirectory becomes a category of the post.
For example, the post 2016-06-08-my_title.md in this directory structure
/docs/science/_posts/2016-06-08-my_title.md automatically gets the
categories docs and science.
.
└── docs
├── index.md
└── science
├── index.md
└── _posts
└── 2016-06-08-my_title.md
Then a breadcrumb included in each post/category layout, can automatically generate a link to each path of the structure
Breadcrumb code
The breadcrumbs code should be placed at /_includes/breadcrumbs.html:
{% assign categories = include.path | split:"/" %}
{% assign filename_without_extension = categories | last | split:"." | first %}
{% if categories contains "_posts" or filename_without_extension == "index" %}
{% comment %} posts are like /docs/python/_posts/2016-06-06-foobar.md {% endcomment %}
{% comment %} OR pages are index.* i.e.: like /docs/python/index.md or index.html {% endcomment %}
{% assign categories = categories | pop %}
{% endif %}
{% assign route="" %}
<a href="{{ '/' | absolute_url }}">Home</a>
{% for category in categories %}
<span class="prompt">>></span>
{% assign route = route | append: '/' | append: category %}
{% if forloop.last %}
{% if include.title %}{{include.title}}{% else %}{{ category }}{% endif %}
{% else %}
<a href="{{ route | absolute_url }}">{{ category }}</a>
{% endif %}
{% endfor %}
Posts layouts
Each layout used in category pages and posts should include
the breadcrumbs.html code, with the current page path and title
parameters.
In /_layouts/post.html:
..
{% include breadcrumbs.html path=page.path title=page.title %}
..
Output
The previous scheme would generate the following breadcrumb for each case.
| URL | Generated Breadcrumb | Served Filename |
|---|---|---|
| / | home | index.html |
| /docs | home > docs | docs/index.md |
| /docs/science | home > docs > science | docs/science/index.md |
| /docs/about | home > about | docs/about.md |
| /docs/science/my_title * | home > docs > science > my title | docs/science/_posts/2016-06-08-my_title.md |
(*) Using titles without dates in _config.yml with permalink: /:title/
If page does not have a title variable in front matter, then its filename will be displayed in breadcrumbs.
You can see this in action in the jekyll-skeleton example website.