class RDoc::Markup

RDoc::Markup parses plain text documents and attempts to decompose them into their constituent parts. Some of these parts are high-level: paragraphs, chunks of verbatim text, list entries and the like. Other parts happen at the character level: a piece of bold text, a word in code font. This markup is similar in spirit to that used on WikiWiki webs, where folks create web pages using a simple set of formatting rules.

RDoc::Markup and other markup formats do no output formatting, this is handled by the RDoc::Markup::Formatter subclasses.

Supported Formats

Besides the RDoc::Markup format, the following formats are built in to RDoc:


The markdown format as described by See RDoc::Markdown for details on the parser and supported extensions.


The rdtool format. See RDoc::RD for details on the parser and format.


The TomDoc format as described by See RDoc::TomDoc for details on the parser and supported extensions.

You can choose a markup format using the following methods:

per project

If you build your documentation with rake use RDoc::Task#markup.

If you build your documentation by hand run:

rdoc --markup your_favorite_format --write-options

and commit .rdoc_options and ship it with your packaged gem.

per file

At the top of the file use the :markup: directive to set the default format for the rest of the file.

per comment

Use the :markup: directive at the top of a comment you want to write in a different format.


RDoc::Markup is extensible at runtime: you can add new markup elements to be recognized in the documents that RDoc::Markup parses.

RDoc::Markup is intended to be the basis for a family of tools which share the common requirement that simple, plain-text should be rendered in a variety of different output formats and media. It is envisaged that RDoc::Markup could be the basis for formatting RDoc style comment blocks, Wiki entries, and online FAQs.


This code converts input_string to HTML. The conversion takes place in the convert method, so you can use the same RDoc::Markup converter to convert multiple input strings.

require 'rdoc'

h =

puts h.convert(input_string)

You can extend the RDoc::Markup parser to recognize new markup sequences, and to add regexp handling. Here we make WikiWords significant to the parser, and also make the sequences {word} and <no>text…</no> signify strike-through text. We then subclass the HTML output class to deal with these:

require 'rdoc'

class WikiHtml < RDoc::Markup::ToHtml
  def handle_regexp_WIKIWORD(target)
    "<font color=red>" + target.text + "</font>"

markup =
markup.add_word_pair("{", "}", :STRIKE)
markup.add_html("no", :STRIKE)

markup.add_regexp_handling(/\b([A-Z][a-z]+[A-Z]\w+)/, :WIKIWORD)

wh =, markup
wh.add_tag(:STRIKE, "<strike>", "</strike>")

puts "<body>#{wh.convert}</body>"


Where Encoding support is available, RDoc will automatically convert all documents to the same output encoding. The output encoding can be set via RDoc::Options#encoding and defaults to Encoding.default_external.

RDoc Markup Reference

Block Markup

Paragraphs and Verbatim

The markup engine looks for a document's natural left margin. This is used as the initial margin for the document.

Consecutive lines starting at this margin are considered to be a paragraph. Empty lines separate paragraphs.

Any line that starts to the right of the current margin is treated as verbatim text. This is useful for code listings:

3.times { puts "Ruby" }

In verbatim text, two or more blank lines are collapsed into one, and trailing blank lines are removed:

This is the first line

This is the second non-blank line,
after 2 blank lines in the source markup.

There were two trailing blank lines right above this paragraph, that have been removed. In addition, the verbatim text has been shifted left, so the amount of indentation of verbatim text is unimportant.

For HTML output RDoc makes a small effort to determine if a verbatim section contains Ruby source code. If so, the verbatim block will be marked up as HTML. Triggers include “def”, “class”, “module”, “require”, the “hash rocket”# (=>) or a block call with a parameter.


A line starting with an equal sign (=) is treated as a heading. Level one headings have one equals sign, level two headings have two, and so on until level six, which is the maximum (seven hyphens or more result in a level six heading).

For example, the above header was obtained with:

=== Headers

In HTML output headers have an id matching their name. The above example's HTML is:

<h3 id="label-Headers">Headers</h3>

If a heading is inside a method body the id will be prefixed with the method's id. If the above header where in the documentation for a method such as:

# This method does fun things
# = Example
#   Example of fun things goes here ...

def do_fun_things

The header's id would be:

<h1 id="method-i-do_fun_things-label-Example">Example</h1>

The label can be linked-to using SomeClass@Headers. See Links for further details.


A line starting with three or more hyphens (at the current indent) generates a horizontal rule.



Simple Lists

If a paragraph starts with a “*”, “-”, “<digit>.” or “<letter>.”, then it is taken to be the start of a list. The margin is increased to be the first non-space following the list start flag. Subsequent lines should be indented to this new margin until the list ends. For example:

* this is a list with three paragraphs in
  the first item.  This is the first paragraph.

  And this is the second paragraph.

  1. This is an indented, numbered list.
  2. This is the second item in that list

  This is the third conventional paragraph in the
  first list item.

* This is the second item in the original list


Labeled Lists

You can also construct labeled lists, sometimes called description or definition lists. Do this by putting the label in square brackets and indenting the list body:

[cat]  a small furry mammal
       that seems to sleep a lot

[ant]  a little insect that is known
       to enjoy picnics



a small furry mammal that seems to sleep a lot


a little insect that is known to enjoy picnics

If you want the list bodies to line up to the left of the labels, use two colons:

cat::  a small furry mammal
       that seems to sleep a lot

ant::  a little insect that is known
       to enjoy picnics



a small furry mammal that seems to sleep a lot


a little insect that is known to enjoy picnics

Notice that blank lines right after the label are ignored in labeled lists:


    definition 1


    definition 2

produces the same output as

[one]  definition 1
[two]  definition 2

Lists and Verbatim

If you want to introduce a verbatim section right after a list, it has to be less indented than the list item bodies, but more indented than the list label, letter, digit or bullet. For instance:

*   point 1

*   point 2, first paragraph

    point 2, second paragraph
      verbatim text inside point 2
    point 2, third paragraph
  verbatim text outside of the list (the list is therefore closed)
regular paragraph after the list


verbatim text outside of the list (the list is therefore closed)

regular paragraph after the list

Text Markup

Bold, Italic, Typewriter Text

You can use markup within text (except verbatim) to change the appearance of parts of that text. Out of the box, RDoc::Markup supports word-based and general markup.

Word-based markup uses flag characters around individual words:


displays word in a bold font


displays word in an emphasized font


displays word in a code font

General markup affects text between a start delimiter and an end delimiter. Not surprisingly, these delimiters look like HTML markup.


displays text in a bold font


displays text in an emphasized font (alternate tag: <i>)


displays text in a code font (alternate tag: <code>)

Unlike conventional Wiki markup, general markup can cross line boundaries. You can turn off the interpretation of markup by preceding the first character with a backslash (see Escaping Text Markup, below).

Links to starting with http:, https:, mailto:, ftp: or www. are recognized. An HTTP url that references an external image is converted into an inline image element.

Classes and methods will be automatically linked to their definition. For example, RDoc::Markup will link to this documentation. By default methods will only be automatically linked if they contain an _ (all methods can be automatically linked through the --hyperlink-all command line option).

Single-word methods can be linked by using the # character for instance methods or :: for class methods. For example, #convert links to convert. A class or method may be combined like RDoc::Markup#convert.

A heading inside the documentation can be linked by following the class or method by an @ then the heading name. RDoc::Markup@Links will link to this section like this: Links at RDoc::Markup. Spaces in headings with multiple words must be escaped with + like RDoc::Markup@Escaping+Text+Markup. Punctuation and other special characters must be escaped like CGI.escape.

The @ can also be used to link to sections. If a section and a heading share the same name the section is preferred for the link.

Links can also be of the form label[url], in which case label is used in the displayed text, and url is used as the target. If label contains multiple words, put it in braces: {multi word label}[url]. The url may be an http:-type link or a cross-reference to a class, module or method with a label.

Links with the rdoc-image: scheme will create an image tag for HTML output. Only fully-qualified URLs are supported.

Links with the rdoc-ref: scheme will link to the referenced class, module, method, file, etc. If the referenced item is does not exist no link will be generated and rdoc-ref: will be removed from the resulting text.

Links starting with rdoc-label:label_name will link to the label_name. You can create a label for the current link (for bidirectional links) by supplying a name for the current link like rdoc-label:label-other:label-mine

Links starting with link: refer to local files whose path is relative to the --op directory. Use rdoc-ref: instead of link: to link to files generated by RDoc as the link target may be different across RDoc generators.

Example links:
{RDoc Documentation}[]
{RDoc Markup}[rdoc-ref:RDoc::Markup]

Escaping Text Markup

Text markup can be escaped with a backslash, as in <tt>, which was obtained with \<tt>. Except in verbatim sections and between <tt> tags, to produce a backslash you have to double it unless it is followed by a space, tab or newline. Otherwise, the HTML formatter will discard it, as it is used to escape potential links:

* The \ must be doubled if not followed by white space: \\.
* But not in \<tt> tags: in a Regexp, <tt>\S</tt> matches non-space.
* This is a link to {ruby-lang}[].
* This is not a link, however: \{}[].
* This will not be linked to \RDoc::RDoc#document


Inside <tt> tags, more precisely, leading backslashes are removed only if followed by a markup character (<*_+), a backslash, or a known link reference (a known class or method). So in the example above, the backslash of \S would be removed if there was a class or module named S in the current context.

This behavior is inherited from RDoc version 1, and has been kept for compatibility with existing RDoc documentation.

Conversion of characters

HTML will convert two/three dashes to an em-dash. Other common characters are converted as well:

em-dash::  -- or ---
ellipsis:: ...

single quotes:: 'text' or `text'
double quotes:: "text" or ``text''

copyright:: (c)
registered trademark:: (r)



– or —


single quotes

'text' or `text'

double quotes

“text” or “text''



registered trademark


Documenting Source Code

Comment blocks can be written fairly naturally, either using # on successive lines of the comment, or by including the comment in a =begin/=end block. If you use the latter form, the =begin line must be flagged with an rdoc tag:

=begin rdoc
Documentation to be processed by RDoc.


RDoc stops processing comments if it finds a comment line starting with -- right after the # character (otherwise, it will be treated as a rule if it has three dashes or more). This can be used to separate external from internal comments, or to stop a comment being associated with a method, class, or module. Commenting can be turned back on with a line that starts with ++.

# Extract the age and calculate the date-of-birth.
# FIXME: fails if the birthday falls on February 29th
# The DOB is returned as a Time object.

def get_dob(person)
  # ...

Names of classes, files, and any method names containing an underscore or preceded by a hash character are automatically linked from comment text to their description. This linking works inside the current class or module, and with ancestor methods (in included modules or in the superclass).

Method parameter lists are extracted and displayed with the method description. If a method calls yield, then the parameters passed to yield will also be displayed:

def fred
  yield line, address

This will get documented as:

fred() { |line, address| ... }

You can override this using a comment containing ':yields: …' immediately after the method definition

def fred # :yields: index, position
  # ...

  yield line, address

which will get documented as

fred() { |index, position| ... }

:yields: is an example of a documentation directive. These appear immediately after the start of the document element they are modifying.

RDoc automatically cross-references words with underscores or camel-case. To suppress cross-references, prefix the word with a \ character. To include special characters like “\n”, you'll need to use two \ characters in normal text, but only one in <tt> text:

"\\n" or "<tt>\n</tt>"


“\n” or “\n


Directives are keywords surrounded by “:” characters.

Controlling what is documented

:nodoc: / :nodoc: all

This directive prevents documentation for the element from being generated. For classes and modules, methods, aliases, constants, and attributes directly within the affected class or module also will be omitted. By default, though, modules and classes within that class or module will be documented. This is turned off by adding the all modifier.

module MyModule # :nodoc:
  class Input

module OtherModule # :nodoc: all
  class Output

In the above code, only class MyModule::Input will be documented.

The :nodoc: directive, like :enddoc:, :stopdoc: and :startdoc: presented below, is local to the current file: if you do not want to document a module that appears in several files, specify :nodoc: on each appearance, at least once per file.

:stopdoc: / :startdoc:

Stop and start adding new documentation elements to the current container. For example, if a class has a number of constants that you don't want to document, put a :stopdoc: before the first, and a :startdoc: after the last. If you don't specify a :startdoc: by the end of the container, disables documentation for the rest of the current file.


Forces a method or attribute to be documented even if it wouldn't be otherwise. Useful if, for example, you want to include documentation of a particular private method.


Document nothing further at the current level: directives :startdoc: and :doc: that appear after this will not be honored for the current container (file, class or module), in the current file.

:notnew: / :not_new: / :not-new:

Only applicable to the initialize instance method. Normally RDoc assumes that the documentation and parameters for initialize are actually for the new method, and so fakes out a new for the class. The :notnew: directive stops this. Remember that initialize is private, so you won't see the documentation unless you use the -a command line option.

Method arguments

:arg: or :args: parameters

Overrides the default argument handling with exactly these parameters.

#  :args: a, b

def some_method(*a)
:yield: or :yields: parameters

Overrides the default yield discovery with these parameters.

# :yields: key, value

def each_thing &block

Lines up to the next blank line or lines with a common prefix in the comment are treated as the method's calling sequence, overriding the default parsing of method parameters and yield arguments.

Multiple lines may be used.

# :call-seq:
#   ARGF.readlines(sep=$/)     -> array
#   ARGF.readlines(limit)      -> array
#   ARGF.readlines(sep, limit) -> array
#   ARGF.to_a(sep=$/)     -> array
#   ARGF.to_a(limit)      -> array
#   ARGF.to_a(sep, limit) -> array
# The remaining lines are documentation ...


Sections allow you to group methods in a class into sensible containers. If you use the sections 'Public', 'Internal' and 'Deprecated' (the three allowed method statuses from TomDoc) the sections will be displayed in that order placing the most useful methods at the top. Otherwise, sections will be displayed in alphabetical order.

:category: section

Adds this item to the named section overriding the current section. Use this to group methods by section in RDoc output while maintaining a sensible ordering (like alphabetical).

# :category: Utility Methods
# CGI escapes +text+

def convert_string text
  CGI.escapeHTML text

An empty category will place the item in the default category:

# :category:
# This method is in the default category

def some_method
  # ...

Unlike the :section: directive, :category: is not sticky. The category only applies to the item immediately following the comment.

Use the :section: directive to provide introductory text for a section of documentation.

:section: title

Provides section introductory text in RDoc output. The title following :section: is used as the section name and the remainder of the comment containing the section is used as introductory text. A section's comment block must be separated from following comment blocks. Use an empty title to switch to the default section.

The :section: directive is sticky, so subsequent methods, aliases, attributes, and classes will be contained in this section until the section is changed. The :category: directive will override the :section: directive.

A :section: comment block may have one or more lines before the :section: directive. These will be removed, and any identical lines at the end of the block are also removed. This allows you to add visual cues to the section.


# ----------------------------------------
# :section: My Section
# This is the section that I wrote.
# See it glisten in the noon-day sun.
# ----------------------------------------

# Comment for some_method

def some_method
  # ...

Other directives

:markup: type

Overrides the default markup type for this comment with the specified markup type. For Ruby files, if the first comment contains this directive it is applied automatically to all comments in the file.

Unless you are converting between markup formats you should use a .rdoc_options file to specify the default documentation format for your entire project. See Saved Options at RDoc::Options for instructions.

At the top of a file the :markup: directive applies to the entire file:

# coding: UTF-8
# :markup: TomDoc

# TomDoc comment here ...

class MyClass
  # ...

For just one comment:

  # ...

# :markup: RDoc
# This is a comment in RDoc markup format ...

def some_method
  # ...

See CONTRIBUTING at Markup for instructions on adding a new markup format.

:include: filename

Include the contents of the named file at this point. This directive must appear alone on one line, possibly preceded by spaces. In this position, it can be escaped with a \ in front of the first colon.

The file will be searched for in the directories listed by the --include option, or in the current directory by default. The contents of the file will be shifted to have the same indentation as the ':' at the start of the :include: directive.

:title: text

Sets the title for the document. Equivalent to the --title command line parameter. (The command line parameter overrides any :title: directive in the source).

:main: name

Equivalent to the --main command line parameter.



An AttributeManager which handles inline markup.

Public Class Methods

new(attribute_manager = nil) click to toggle source

Take a block of text and use various heuristics to determine its structure (paragraphs, lists, and so on). Invoke an event handler as we identify significant chunks.

# File lib/rdoc/markup.rb, line 777
def initialize attribute_manager = nil
  @attribute_manager = attribute_manager ||
  @output = nil
parse(str) click to toggle source

Parses str into an RDoc::Markup::Document.

# File lib/rdoc/markup.rb, line 747
  def self.parse str
    RDoc::Markup::Parser.parse str
  rescue RDoc::Markup::Parser::Error => e
    $stderr.puts <<-EOF
While parsing markup, RDoc encountered a #{e.class}:

\tfrom #{e.backtrace.join "\n\tfrom "}




Please file a bug report with the above information at:


Public Instance Methods

add_html(tag, name) click to toggle source

Add to the sequences recognized as general markup.

# File lib/rdoc/markup.rb, line 794
def add_html(tag, name)
  @attribute_manager.add_html(tag, name)
add_regexp_handling(pattern, name) click to toggle source

Add to other inline sequences. For example, we could add WikiWords using something like:

parser.add_regexp_handling(/\b([A-Z][a-z]+[A-Z]\w+)/, :WIKIWORD)

Each wiki word will be presented to the output formatter.

# File lib/rdoc/markup.rb, line 806
def add_regexp_handling(pattern, name)
  @attribute_manager.add_regexp_handling(pattern, name)
add_word_pair(start, stop, name) click to toggle source

Add to the sequences used to add formatting to an individual word (such as bold). Matching entries will generate attributes that the output formatters can recognize by their name.

# File lib/rdoc/markup.rb, line 787
def add_word_pair(start, stop, name)
  @attribute_manager.add_word_pair(start, stop, name)
convert(input, formatter) click to toggle source

We take input, parse it if necessary, then invoke the output formatter using a Visitor to render the result.

# File lib/rdoc/markup.rb, line 814
def convert input, formatter
  document = case input
             when RDoc::Markup::Document then
               RDoc::Markup::Parser.parse input

  document.accept formatter