calavera-jekyll

h1. Jekyll

Jekyll is a simple, blog aware, static site generator. It takes a template directory (representing the raw form of a website), runs it through Textile or Markdown and Liquid converters, and spits out a complete, static website suitable for serving with Apache or your favorite web server. Visit "http://tom.preston-werner.com":http://tom.preston-werner.com to see an example of a Jekyll generated blog.

To understand how this all works, open up my "TPW":http://github.com/mojombo/tpw repo in a new browser window. I'll be referencing the code there.

Take a look at "index.html":http://github.com/mojombo/tpw/tree/master/index.html. This file represents the homepage of the site. At the top of the file is a chunk of YAML that contains metadata about the file. This data tells Jekyll what layout to give the file, what the page's title should be, etc. In this case, I specify that the "default" template should be used. You can find the layout files in the "_layouts":http://github.com/mojombo/tpw/tree/master/_layouts directory. If you open "default.html":http://github.com/mojombo/tpw/tree/master/_layouts/default.html you can see that the homepage is constructed by wrapping index.html with this layout.

You'll also notice Liquid templating code in these files. "Liquid":http://www.liquidmarkup.org/ is a simple, extensible templating language that makes it easy to embed data in your templates. For my homepage I wanted to have a list of all my blog posts. Jekyll hands me a Hash containing various data about my site. A reverse chronological list of all my blog posts can be found in site.posts. Each post, in turn, contains various fields such as title and date.

Jekyll gets the list of blog posts by parsing the files in any "_posts":http://github.com/mojombo/tpw/tree/master/_posts directory found in subdirectories below the root. Each post's filename contains (by default) the publishing date and slug (what shows up in the URL) that the final HTML file should have. Open up the file corresponding to a blog post: "2008-11-17-blogging-like-a-hacker.textile":http://github.com/mojombo/tpw/tree/master/_posts/2008-11-17-blogging-like-a-hacker.textile. GitHub renders textile files by default, so to better understand the file, click on the "raw":http://github.com/mojombo/tpw/tree/master/_posts/2008-11-17-blogging-like-a-hacker.textile?raw=true view to see the original file. Here I've specified the post layout. If you look at that file you'll see an example of a nested layout. Layouts can contain other layouts allowing you a great deal of flexibility in how pages are assembled. In my case I use a nested layout in order to show related posts for each blog entry. The YAML also specifies the post's title which is then embedded in the post's body via Liquid.

Posts are handled in a special way by Jekyll. The date you specify in the filename is used to construct the URL in the generated site. The example post, for instance, ends up at http://tom.preston-werner.com/2008/11/17/blogging-like-a-hacker.html.

Categories for posts are derived from the directory structure the posts were found within. A post that appears in the directory foo/bar/_posts is placed in the categories 'foo' and 'bar'. By selecting posts from particular categories in your Liquid templates, you will be able to host multiple blogs within a site.

Files that do not reside in directories prefixed with an underscore are mirrored into a corresponding directory structure in the generated site. If a file does not have a YAML preface, it is not run through the Liquid interpreter. Binary files are copied over unmodified.

Jekyll is still a very young project. I've only developed the exact functionality that I've needed. As time goes on I'd like to see the project mature and support additional features. If you end up using Jekyll for your own blog, drop me a line and let me know what you'd like to see in future versions. Better yet, fork the project over at GitHub and hack in the features yourself!

h2. Example Proto-Site

My own personal site/blog is generated with Jekyll.

The proto-site repo ("http://github.com/mojombo/tpw":http://github.com/mojombo/tpw) is converted into the actual site ("http://tom.preston-werner.com/":http://tom.preston-werner.com)

h2. Install

The best way to install Jekyll is via RubyGems:

$ sudo gem install mojombo-jekyll -s http://gems.github.com/

Jekyll requires the gems directory_watcher, liquid, open4, and maruku (for markdown support). These are automatically installed by the gem install command.

Maruku comes with optional support for LaTeX to PNG rendering via "blahtex":http://gva.noekeon.org/blahtexml/ (Version 0.6) which must be in your $PATH along with dvips.

(NOTE: the version of maruku I am using is remi-maruku on GitHub as it does not assume a fixed location for dvips.)

h2. Run

$ cd /path/to/proto/site $ jekyll

This will generate the site and place it in /path/to/proto/site/_site. If you'd like the generated site placed somewhere else:

$ jekyll /path/to/place/generated/site

And if you don't want to be in the proto site root to run Jekyll:

$ jekyll /path/to/proto/site /path/to/place/generated/site

h2. Run Options

h3. Autobuild

There is an autobuild feature that will regenerate your site if any of the files change. The autobuild feature can be used on any of the invocations:

$ jekyll --auto

h3. Related Posts

By default, the "related posts" functionality will produce crappy results. In order to get high quality results with a true LSI algorithm, you must enable it (it may take some time to run if you have many posts):

$ jekyll --lsi

h3. Code Highlighting

For static code highlighting, you can install Pygments (see below) and then use that to make your code blocks look pretty. To activate Pygments support during the conversion:

$ jekyll --pygments

h3. Markdown Processor

By default, Jekyll uses "Maruku":http://maruku.rubyforge.org (pure Ruby) for Markdown support. If you'd like to use RDiscount (faster, but requires compilation), you must install it (gem install rdiscount) and then you can have it used instead:

$ jekyll --rdiscount

h3. Local Server

When previewing complex sites locally, simply opening the site in a web browser (using file://) can cause problems with links that are relative to the site root (e.g., "/stylesheets/style.css"). To get around this, Jekyll can launch a simple WEBrick server (works well in conjunction with --auto). Default port is 4000:

$ jekyll --server [PORT]

h3. Permalink Style

By default, the permalink for each post begins with its date in 'YYYY/MM/DD' format.

If you do not wish to have the date appear in the URL of each post, you can change the permalink style to 'none' so that only the 'slug' part of the filename is used. For example, with the permalink style set to 'none' the file '2009-01-01-happy-new-year.markdown' will have a permalink like 'http://yoursite.com/happy-new-year.html'. The date of the post will still be read from the filename (and is required!) to be used elsewhere in Jekyll.

If you want WordPress-style pretty URLs that leave off the .html, you can change the permalink style to 'pretty' and directories corresponding to the date parts and post name will be made and an index.html will be placed in the leaf directory resulting in URLs like 2008/11/17/blogging-like-a-hacker/.

$ jekyll --permalink [date|none|pretty]

There is also an option to paginate the blog's post. With this option enabled, Jekyll takes the index.html file in your base directory and compiles it within several directories called "page2", "page3" .. "pageN".

$ jekyll --paginate [PER_PAGE]

h3. Using jekyll.ini to add more run options

The jekyll.ini file allows you to add more run options. You have to add this file in your root directory. This is quite useful if you don't run jekyll directly, for instance if you use github-pages but you want to add more options to the default run command.

h2. Data

Jekyll traverses your site looking for files to process. Any files with YAML front matter (see below) are subject to processing. For each of these files, Jekyll makes a variety of data available to the pages via the Liquid templating system. The following is a reference of the available data.

h3. Global

site Sitewide information.

page For Posts, this is the union of the data in the YAML front matter and the computed data (such as URL and date). For regular pages, this is just the YAML front matter.

content In layout files, this contains the content of the subview(s). In Posts or Pages, this is undefined.

paginator Page information available when we use the paginate option. It includes the posts within that page, the number of the previous and next pages and other info that you can see in Jekyll::Site.paginate_posts.

h3. Site

site.time The current Time (when you run the jekyll command).

site.posts A reverse chronological list of all Posts.

site.related_posts If the page being processed is a Post, this contains a list of up to ten related Posts. By default, these are low quality but fast to compute. For high quality but slow to compute results, run the jekyll command with the --lsi (latent semantic indexing) option.

site.categories.CATEGORY The list of all Posts in category CATEGORY.

h3. Post

post.title The title of the Post.

post.url The URL of the Post without the domain. e.g. /2008/12/14/my-post.html

post.date The Date assigned to the Post.

post.id An identifier unique to the Post (useful in RSS feeds). e.g. /2008/12/14/my-post

post.categories The list of categories to which this post belongs. Categories are derived from the directory structure above the _posts directory. For example, a post at /work/code/_posts/2008-12-24-closures.textile would have this field set to ['work', 'code'].

post.topics The list of topics for this Post. Topics are derived from the directory structure beneath the _posts directory. For example, a post at /_posts/music/metal/2008-12-24-metalocalypse.textile would have this field set to ['music', 'metal'].

post.content The content of the Post.

h3. Paginator

paginator.page The number of the current page.

paginator.per_page Number of posts per page.

paginator.posts Posts available for that page.

paginator.total_posts Total number of posts.

paginator.total_pages Total number of pages.

paginator.previous_page The number of the previous page.

paginator.next_page The number of the next page.

h2. YAML Front Matter

Any files that contain a YAML front matter block will be processed by Jekyll as special files. The front matter must be the first thing in the file and takes the form of:

---
layout: post
title: Blogging Like a Hacker
---

Between the triple-dashed lines, you can set predefined variables (see below for a reference) or custom data of your own.

h3. Predefined Global Variables

layout If set, this specifies the layout file to use. Use the layout file name without file extension. Layout files must be placed in the _layouts directory.

h3. Predefined Post Variables

permalink If you need your processed URLs to be something other than the default /year/month/day/title.html then you can set this variable and it will be used as the final URL.

published Set to false if you don't want a post to show up when the site is generated.

category/categories Instead of placing posts inside of folders, you can specify one or more categories that the post belongs to. When the site is generated the post will act as though it had been set with these categories normally.

h3. Custom Variables

Any variables in the front matter that are not predefined are mixed into the data that is sent to the Liquid templating engine during the conversion. For instance, if you set a title, you can use that in your layout to set the page title:

{{ page.title }}

h2. Filters, Tags, and Blocks

In addition to the built-in Liquid filters, tags, and blocks, Jekyll provides some additional items that you can use in your site.

h3. Date to XML Schema (Filter)

Convert a Time into XML Schema format.

{{ site.time | date_to_xmlschema }}

becomes

2008-11-17T13:07:54-08:00

h3. XML Escape (Filter)

Escape some text for use in XML.

{{ post.content | xml_escape }}

h3. Number of Words (Filter)

Count the number of words in some text.

{{ post.content | number_of_words }}

becomes

1337

h3. Array to Sentence String

Convert an array into a sentence.

{{ page.tags | array_to_sentence_string }}

becomes

foo, bar, and baz

h3. Textilize

Convert a Textile-formatted string into HTML, formatted via RedCloth

{{ page.excerpt | textilize }}

h3. Include (Tag)

If you have small page fragments that you wish to include in multiple places on your site, you can use the include tag.

{% include sig.textile %}

Jekyll expects all include files to be placed in an _includes directory at the root of your source dir. So this will embed the contents of /path/to/proto/site/_includes/sig.textile into the calling file.

h3. Code Highlighting (Block)

Jekyll has built in support for syntax highlighting of over "100 languages":http://pygments.org/languages/ via "Pygments":http://pygments.org/. In order to take advantage of this you'll need to have Pygments installed, and the pygmentize binary must be in your path. When you run Jekyll, make sure you run it with Pygments support:

$ jekyll --pygments

To denote a code block that should be highlighted:

{% highlight ruby %}
def foo
  puts 'foo'
end
{% endhighlight %}

The argument to highlight is the language identifier. To find the appropriate identifier to use for your favorite language, look for the "short name" on the "Lexers":http://pygments.org/docs/lexers/ page.

There is a second argument to highlight called linenos that is optional. Including the linenos argument will force the highlighted code to include line numbers. For instance, the following code block would include line numbers next to each line:

{% highlight ruby linenos %}
def foo
  puts 'foo'
end
{% endhighlight %}

In order for the highlighting to show up, you'll need to include a highlighting stylesheet. For an example stylesheet you can look at "syntax.css":http://github.com/mojombo/tpw/tree/master/css/syntax.css. These are the same styles as used by GitHub and you are free to use them for your own site. If you use linenos, you might want to include an additional CSS class definition for lineno in syntax.css to distinguish the line numbers from the highlighted code.

h2. Categories

Posts are placed into categories based on the directory structure they are found within (see above for an example). The categories can be accessed from within a Liquid template as follows:

{% for post in site.categories.foo %}
  
{{ post.date | date_to_string }} - {{ post.title }}
{% endfor %}

This would list all the posts in the category 'foo' by date and title.

The posts within each category are sorted in reverse chronological order.

h2. Blog migrations

h3. Movable Type

To migrate your MT blog into Jekyll, you'll need read access to the database. The lib/jekyll/converters/mt.rb module provides a simple convert to create .markdown files in a _posts directory based on the entries contained therein.

$ export DB=my_mtdb $ export USER=dbuser $ export PASS=dbpass $ ruby -r './lib/jekyll/converters/mt' -e 'Jekyll::MT.process(
"#{ENV["DB"]}", "#{ENV["USER"]}", "#{ENV["PASS"]}")'

You may need to adjust the SQL query used to retrieve MT entries. Left alone, it will attempt to pull all entries across all blogs regardless of status. Please check the results and verify the posts before publishing.

h3. Typo 4+

To migrate your Typo blog into Jekyll, you'll need read access to the MySQL database. The lib/jekyll/converters/typo.rb module provides a simple convert to create .html, .textile, or .markdown files in a _posts directory based on the entries contained therein.

$ export DB=my_typo_db $ export USER=dbuser $ export PASS=dbpass $ ruby -r './lib/jekyll/converters/typo' -e 'Jekyll::Typo.process(
"#{ENV["DB"]}", "#{ENV["USER"]}", "#{ENV["PASS"]}")'

You may need to adjust the code used to filter Typo entries. Left alone, it will attempt to pull all entries across all blogs that were published. This code also has only been tested with Typo version 4+. Previous versions of Typo may not convert correctly. Please check the results and verify the posts before publishing.

h3. TextPattern 4

To migrate your TextPattern blog into Jekyll, you'll need read access to the MySQL database. The lib/jekyll/converters/textpattern.rb module provides a simple convert to create .textile files in a _posts directory based on the entries contained therein.

$ ruby -r './lib/jekyll/converters/textpattern' -e 'Jekyll::TextPattern.process(
"database_name", "username", "password", "hostname")'

The hostname defaults to localhost, all other variables are needed You may need to adjust the code used to filter entries. Left alone, it will attempt to pull all entries that are live or sticky.

h2. Contribute

If you'd like to hack on Jekyll, start by forking my repo on GitHub:

http://github.com/mojombo/jekyll

To get all of the dependencies, install the gem first. The best way to get your changes merged back into core is as follows:

Clone down your fork

Create a topic branch to contain your change

Hack away

Add tests and make sure everything still passes by running rake

If you are adding new functionality, document it in README.textile

Do not change the version number, I will do that on my end

If necessary, rebase your commits into logical chunks, without errors

Push the branch up to GitHub

Send me (mojombo) a pull request for your branch

h2. License

(The MIT License)

Copyright (c) 2008 Tom Preston-Werner

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.