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Highlight is a simple syntax highlighting gem for Ruby and Rails. It's basically a wrapper around the popular http://pygments.org highlighter that's written in Python and supports an impressive number of languages.

If pygments is installed on the machine and in the PATH, that binary is used, otherwise the plugin falls back to the web API at http://pygments.simplabs.com/, created by Trevor Turk.

See the API docs at http://rdoc.info/projects/simplabs/highlight.


Highlight can either be used standalone via

require 'simplabs/highlight'
Simplabs::Highlight.highlight(:ruby, 'class Test; end')

or in Rails where it adds the highlight_code helper:

highlight_code(language, code = nil, &block)

language may be either a Symbol or a String (see supported languages below). The code can be passed either as a string or inside a block, e.g.:

highlight_code(:ruby, 'class Test; end')


highlight_code(:ruby) do
  klass = 'class'
  name  = 'Test'
  _end  = 'end'
  "#{klass} #{name}; #{_end}"

Since highlighting the code takes a while, all highlighted source code should be cached, e.g.:

<%- code = 'class Test; end' -%>
<%- cache Digest::SHA1.hexdigest(code) do -%>
  <%= highlight_code(:ruby, code) -%>
<%- end -%>

Supported Languages

The following languages are supported (there are probably more that are supported by pygments). All of the paranthesized identifiers may be used as parameters for highlight to denote the language the source code to highlight is written in (use either Symbols or Strings).

  • Actionscript (as, as3, actionscript)
  • Applescript (applescript)
  • bash (bash, sh)
  • C (c, h)
  • Clojure (clojure)
  • C++ (c++, cpp, hpp)
  • C# (c#, csharp, cs)
  • CSS (css)
  • diff (diff)
  • Dylan (dylan)
  • Erlang (erlang, erl, er)
  • HTML (html, htm)
  • Java (java)
  • JavaScript (javascript, js, jscript)
  • JSP (jsp)
  • Make (make, basemake, makefile)
  • Objective-C (objective-c)
  • OCaml (ocaml)
  • Perl (perl, pl)
  • PHP (php)
  • Python (python, py)
  • RHTML (erb, rhtml)
  • Ruby (ruby, rb)
  • Scala (scala)
  • Scheme (scheme)
  • Smalltalk (smalltalk)
  • Smarty (smarty)
  • SQL (sql)
  • XML (xml, xsd)
  • XSLT (xslt)
  • YAML (yaml, yml)


Installation is as easy as

gem install highlight

To use highlight in Rails apps, you have to define the dependency in the Gemfile:

gem 'highlight', :require => 'simplabs/highlight'

Highlight also comes with a default CSS file that defines styles for the highlighted code. This CSS file can be copied to your application's public/stylesheets directory via

./bin/rails generate highlight_styles

If you don't have python and pygments installed, you will need that too. For instructions on installing pygments, refer to http://pygments.org/docs/installation/.


Copyright (c) 2008-2010 Marco Otte-Witte (http://simplabs.com), released under the MIT license


The actual highlighting is done by Pygments (http://pygments.org).