Modified: Fri Jan 24 09:27:51 CST 2003

RDOC - Ruby Documentation System

This package contains Rdoc and SimpleMarkup. Rdoc is an application that produces documentation for one or more Ruby source files. We work similarly to JavaDoc, parsing the source, and extracting the definition for classes, modules, and methods (along with includes and requires). We associate with these optional documentation contained in the immediately preceding comment block, and then render the result using a pluggable output formatter. (Currently, HTML is the only supported format. Markup is a library that converts plain text into various output formats. The Markup library is used to interpret the comment blocks that Rdoc uses to document methods, classes, and so on.


This distribution contains two packages, rdoc itself and a text markup library, 'markup'. You can install them both using the single command

  % ruby install.rb

in this directory. If you just want to install 'markup', change to the markup directory and run the install.rb script there.



Once installed, you can create documentation using the 'rdoc' command (the command is 'rdoc.rb' under Windows)

  % rdoc [options]  [names...]

Type "rdoc --help" for an up-to-date option summary.

A typical use might be to generate documentation for a package of Ruby source (such as rdoc itself).

  % rdoc

This command generates documentation for all the Ruby and C source files in and below the current directory. These will be stored in a documentation tree starting in the subdirectory 'doc'.

You can make this slightly more useful for your readers by having the index page contain the documentation for the primary file. In our case, we could type

  % rdoc --main rdoc/rdoc.rb

You'll find information on the various formatting tricks you can use in comment blocks in the documentation this generates.

RDoc uses file extensions to determine how to process each file. File names ending .rb and .rbw are assumed to be Ruby source. Files ending .c are parsed as C files. All other files are assumed to contain just SimpleMarkup-style markup (with or without leading '#' comment markers). If directory names are passed to RDoc, they are scanned recursively for C and Ruby source files only.



RDoc is Copyright (c) 2001-2003 Dave Thomas, The Pragmatic Programmers. It is free software, and may be redistributed under the terms specified in the README file of the Ruby distribution.


The Rdoc homepage is There you'll find links for downloading the Rdoc package, and instructions on how to get the still-quivering sources from CVS. I'm also using Sourceforge to track bugs and manage feature requests. If you submit patches, it would help if they were inline (not attachments) and generated using "diff -u". I don't have access to a wide variety of browsers, so reports that output looks funny under Browser XYZ aren't too helpful: far better are suggested changes to the generated HTML that fix the problem.

For other information, feel free to ask on the ruby-talk mailing list (which is mirrored to comp.lang.ruby) or contact


RDoc is invoked from the command line using:

   % rdoc <options> [name...]

Files are parsed, and the information they contain collected, before any output is produced. This allows cross references between all files to be resolved. If a name is a directory, it is traversed. If no names are specified, all Ruby files in the current directory (and subdirectories) are processed.

Options are:

include protected and private methods in the output (by default only public methods are included)
--main name
set the class, module, or file to appear on the index page
--exclude pattern
exclude files and directories matching this pattern from processing
do not display progress messages
place all the output into a single file
--op dir
set the output directory to dir (the default is the directory "doc")
--opname name
set the output name (has no effect for HTML).
--charset charset
Set the character set for the generated HTML.
--fmt fmt
generate output in a particular format.
--include dir,...
specify one or more directories to be searched when satifying given. The directory containing the file currently being processed is always searched.
By default, the source code of methods is shown in a popup. With this option, it's displayed inline.
A name of the form name in a comment is a possible hyperlink to an instance method name. When displayed, the '#' is removed unless this option is specified
--template name
specify an alternate template to use when generating output (the default is 'standard'). This template should be in a directory accessible via $: as rdoc/generators/xxxx_template, where 'xxxx' depends on the output formatter.
include diagrams showing modules and classes. This is currently an experimental feature, and may not be supported by all output templates. You need dot V1.8.6 or later to use the --diagram option correctly (


A typical small Ruby program commented using RDoc might be as follows. You can see the formatted result in EXAMPLE.rb and Anagram.

       # The program takes an initial word or phrase from
       # the command line (or in the absence of a
       # parameter from the first line of standard
       # input).  In then reads successive words or
       # phrases from standard input and reports whether
       # they are angrams of the first word.
       # Author::    Dave Thomas  (mailto:dave@x.y)
       # Copyright:: Copyright (c) 2002 The Pragmatic Programmers, LLC
       # License::   Distributes under the same terms as Ruby

       # This class holds the letters in the original
       # word or phrase. The is_anagram? method allows us
       # to test if subsequent words or phrases are
       # anagrams of the original.
       class Anagram

         # Remember the letters in the initial word
         def initialize(text)
           @initial_letters = letters_of(text)
         # Test to see if a new word contains the same
         # letters as the original
         def is_anagram?(text)
           @initial_letters == letters_of(text)

         # Determine the letters in a word or phrase
         # * all letters are converted to lower case
         # * anything not a letter is stripped out
         # * the letters are converted into an array
         # * the array is sorted
         # * the letters are joined back into a string
         def letters_of(text)

       tester = || gets)
       ARGF.each do |text|
         puts "Anagram! " if tester.is_anagram? text


Comment blocks can be written fairly naturally.

Paragraphs are lines that share the left margin. Text indented past this margin are formatted verbatim.

  1. Lists are typed as indented paragraphs with:
    • a '*' or '-' (for bullet lists)
    • a digit followed by a period for numbered lists

    For example, the input that produced the above paragraph looked like

        1. Lists are typed as indented
           paragraphs with:
           * a '*' or '-' (for bullet lists)
           * a digit followed by a period for
             numbered lists
  2. Labeled lists (sometimes called description lists) are typed using square brackets for the label.
       [cat]   small domestic animal
       [+cat+] command to copy standard input
  3. Labeled lists may also be produced by putting a double colon after the label. This sets the result in tabular form, so the descriptions all line up. This was used to create the 'author' block at the bottom of this description.
       cat::   small domestic animal
       +cat+:: command to copy standard input

    For both kinds of labeled lists, if the body text starts on the same line as the label, then the start of that text determines the block indent for the rest of the body. The text may also start on the line following the label, indented from the start of the label. This is often preferable if the label is long. Both the following are valid labeled list entries:

       <tt>--output</tt> <i>name [, name]</i>::
           specify the name of one or more output files. If multiple
           files are present, the first is used as the index.
       <tt>--quiet:</tt>:: do not output the names, sizes, byte counts,
                           index areas, or bit ratios of units as
                           they are processed.
  4. Headings are entered using equals signs
       = Level One Heading
       == Level Two Heading

    and so on

  5. Rules (horizontal lines) are entered using three or more hyphens.
  6. Non-verbatim text can be marked up:
    italic:word or <em>text</em>
    bold:word or <b>text</b>
    typewriter:word or <tt>text</tt>

    The first form only words around 'words', where a word is a sequence of upper and lower case letters and underscores. Putting a backslash before inline markup stops it being interpreted, which is how I created the table above:

      _italic_::     \_word_ or \<em>text</em>
      *bold*::       \*word* or \<b>text</b>
      +typewriter+:: \+word+ or \<tt>text</tt>
  7. Names of classes, source files, and any method names containing an underscore or preceded by a hash character are automatically hyperlinked from comment text to their description.
  8. Hyperlinks to the web starting http:, mailto:, ftp:, or www. are recognized. An HTTP url that references an external image file is converted into an inline <IMG..>. Hyperlinks starting 'link:' are assumed to refer to local files whose path is relative to the --op directory.

    Hyperlinks can also be of the form label[url], in which case the label is used in the displayed text, and url is used as the target.

  9. 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| ... }
  10. ':yields:' is an example of a documentation modifier. These appear immediately after the start of the document element they are modifying. Other modifiers include
    don't include this element in the documentation. For classes and modules, methods, aliases, and attributes directly within the affected class will also be omitted. By default, though, modules and classes within that class of module will be documented. This is turned off by adding the all modifier.
         module SM  #:nodoc:
           class Input
         module Markup #:nodoc: all
           class Output

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

    force a method to be documented even if it wouldn't otherwise be. Useful is, for example, you want to include documentation of a particular private method.
    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: modifier stops this. Remember that initialize is protected, so you won't see the documentation unless you use the -a command line option.
  11. RDoc stops processing comments if it finds a comment line containing '#--'. 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 '#++'.
        # 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)
  12. Comment blocks can contain other directives:
    include the contents of the named file at this point. 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.
    Sets the title for the document. Equivalent to the --title command line parameter. (The command line parameter overrides any :title: directive in the source).
    Equivalent to the --main command line parameter.

See also markup/simple_markup.rb.

Other stuff

Author:Dave Thomas <>
Requires:Ruby 1.6.5 or later
License:Copyright (c) 2001-2003 Dave Thomas. Released under the same license as Ruby.


This software is provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of merchantibility and fitness for a particular purpose.