module CodeRay

CodeRay Library

CodeRay is a Ruby library for syntax highlighting.

I try to make CodeRay easy to use and intuitive, but at the same time fully featured, complete, fast and efficient.


It consists mainly of

Here’s a fancy graphic to light up this gray docu:


See CodeRay, Encoders, Scanners, Tokens.


Remember you need RubyGems to use CodeRay, unless you have it in your load path. Run Ruby with -rubygems option if required.

Highlight Ruby code in a string as html

require 'coderay'
print CodeRay.scan('puts "Hello, world!"', :ruby).html

# prints something like this:
puts <span class="s">&quot;Hello, world!&quot;<%rspan>

Highlight C code from a file in a html div

require 'coderay'
print CodeRay.scan('ruby.h'), :c).div
print CodeRay.scan_file('ruby.h').html.div

You can include this div in your page. The used CSS styles can be printed with

% coderay_stylesheet

Highlight without typing too much

If you are one of the hasty (or lazy, or extremely curious) people, just run this file:

% ruby -rubygems /path/to/coderay/coderay.rb > example.html

and look at the file it created in your browser.

CodeRay Module

The CodeRay module provides convenience methods for the engine.

You should be able to highlight everything you want just using these methods; so there is no need to dive into CodeRay’s deep class hierarchy.

The examples in the demo directory demonstrate common cases using this interface.

Basic Access Ways

Read this to get a general view what CodeRay provides.


Scanning means analysing an input string, splitting it up into Tokens. Each Token knows about what type it is: string, comment, class name, etc.

Each lang (language) has its own Scanner; for example, :ruby code is handled by CodeRay::Scanners::Ruby.


Scan a string in a given language into Tokens. This is the most common method to use.


Scan a file and guess the language using FileType.

The Tokens object you get from these methods can encode itself; see Tokens.


Encoding means compiling Tokens into an output. This can be colored HTML or LaTeX, a textual statistic or just the number of non-whitespace tokens.

Each Encoder provides output in a specific format, so you select Encoders via formats like :html or :statistic.


Scan and encode a string in a given language.


Encode the given tokens.


Scan a file, guess the language using FileType and encode it.

All-in-One Encoding


Highlight a string with a given input and output format.


You can use an Encoder instance to highlight multiple inputs. This way, the setup for this Encoder must only be done once.


Create an Encoder instance with format and options.


Create an Scanner instance for lang, with ” as default code.

To make use of ::scanner, use CodeRay::Scanner::code=.

The scanning methods provide more flexibility; we recommend to use these.

Reusing Scanners and Encoders

If you want to re-use scanners and encoders (because that is faster), see CodeRay::Duo for the most convenient (and recommended) interface.



A Hash of all known token kinds and their associated CSS classes.


Public Class Methods

coderay_path(*path) click to toggle source

Assuming the path is a subpath of lib/coderay/

# File lib/coderay.rb, line 132
def self.coderay_path *path
  File.join CODERAY_PATH, *path
encode(code, lang, format, options = {}) click to toggle source

Encode a string.

This scans code with the the Scanner for lang and then encodes it with the Encoder for format. options will be passed to the Encoder.

See CodeRay::Encoder.encode.

# File lib/coderay.rb, line 196
def encode code, lang, format, options = {}
  encoder(format, options).encode code, lang, options
encode_file(filename, format, options = {}) click to toggle source

Encodes filename (a path to a code file) with the Scanner for lang.

See ::scan_file. Notice that the second argument is the output format, not the input language.


require 'coderay'
page = CodeRay.encode_file 'some_c_code.c', :html
# File lib/coderay.rb, line 221
def encode_file filename, format, options = {}
  tokens = scan_file filename, :auto, get_scanner_options(options)
  encode_tokens tokens, format, options
encode_tokens(tokens, format, options = {}) click to toggle source

Encode pre-scanned Tokens. Use this together with ::scan:

require 'coderay'

# Highlight a short Ruby code example in a HTML span
tokens = CodeRay.scan '1 + 2', :ruby
puts CodeRay.encode_tokens(tokens, :span)
# File lib/coderay.rb, line 209
def encode_tokens tokens, format, options = {}
  encoder(format, options).encode_tokens tokens, options
encoder(format, options = {}) click to toggle source

Finds the Encoder class for format and creates an instance, passing options to it.


require 'coderay'

stats = CodeRay.encoder(:statistic)
stats.encode("puts 17 + 4\n", :ruby)

puts '%d out of %d tokens have the kind :integer.' % [
#-> 2 out of 4 tokens have the kind :integer.
# File lib/coderay.rb, line 260
def encoder format, options = {}
  Encoders[format].new options
get_scanner_options(options) click to toggle source

Extract the options for the scanner from the options hash.

Returns an empty Hash if :scanner_options is not set.

This is used if a method like ::encode has to provide options for Encoder and scanner.

# File lib/coderay.rb, line 278
def get_scanner_options options
  options.fetch :scanner_options, {}
highlight(code, lang, options = { :css => :class }) click to toggle source

Highlight a string into a HTML <div>.

CSS styles use classes, so you have to include a stylesheet in your output.

See encode.

# File lib/coderay.rb, line 232
def highlight code, lang, options = { :css => :class }, format = :div
  encode code, lang, format, options
highlight_file(filename, options = { :css => :class }) click to toggle source

Highlight a file into a HTML <div>.

CSS styles use classes, so you have to include a stylesheet in your output.

See encode.

# File lib/coderay.rb, line 242
def highlight_file filename, options = { :css => :class }, format = :div
  encode_file filename, format, options
scan(code, lang, options = {}) click to toggle source

Scans the given code (a String) with the Scanner for lang.

This is a simple way to use CodeRay. Example:

require 'coderay'
page = CodeRay.scan("puts 'Hello, world!'", :ruby).html

See also demo/demo_simple.

# File lib/coderay.rb, line 167
def scan code, lang, options = {}, &block
  # FIXME: return a proxy for direct-stream encoding code, lang, options, block
scan_file(filename, lang = :auto, options = {}) click to toggle source

Scans filename (a path to a code file) with the Scanner for lang.

If lang is :auto or omitted, the CodeRay::FileType module is used to determine it. If it cannot find out what type it is, it uses CodeRay::Scanners::Text.

Calls ::scan.


require 'coderay'
page = CodeRay.scan_file('some_c_code.c').html
# File lib/coderay.rb, line 183
def scan_file filename, lang = :auto, options = {}, &block
  lang = FileType.fetch filename, :text, true if lang == :auto
  code = filename
  scan code, lang, options, &block
scanner(lang, options = {}) click to toggle source

Finds the Scanner class for lang and creates an instance, passing options to it.


# File lib/coderay.rb, line 268
def scanner lang, options = {}, &block
  Scanners[lang].new '', options, &block