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Updating documentation

This article describes the current state of the SCons documentation toolchain, as present in versions 2.3.x and higher. It's based on the file doc/overview.rst in the source repository, so go there first to add or change text please.


This text tries to give an overview of the current SCons documentation toolchain. The interested user should be able to better understand where and how the text he writes is processed. It is also a reference for core developers and the release team.

The diagram above roughly shows the steps that we currently need for creating all the MAN pages, User manuals and reference documents. You may think: "Geeez, that looks so complicated. Why can't they simply convert XML files to PDF with Docbook, or use reST?" Please be patient, and continue reading. Things will get a little clearer soon.

Our toolchain doesn't only produce HTML and PDF files that are nice to look at, it also performs a lot of processing under the covers. We try to have our documentation as consistent as possible to the current behaviour of the source code, but this requires some extra steps.

So let's start right at the top...

Writer's view

The toolchain is set up, such that the User has a very restricted view on this whole "document processing thingy". All he should be concerned about is to edit existing text or write new sections and paragraphs. Sometimes even a completely new chapter has to be added, in general he can fire up his XML editor of choice and type away. A few configurations for XML editors supporting WYSIWYG editing are provided, too.

If he is a really nice user, he cares about validating his XML files against our special "SCons Docbook DTD/XSD". Either during typing, supported by his XML editor, or by executing a special script

python bin/

from the top source folder afterwards. Preferably both.

Everything's looking okay, all validation passed? Good, then he simply commits his new work, and creates a pull request on Bitbucket. That's it!

Additionally, he can create the single documents on his side if he wants to get a feel for how the final result looks (and who doesn't?). Each of the document folders (design, developer, man, python10, reference, and user) contains an SConstruct file along with the actual XML files. You can call

python ../../src/script/

from within the directory, and have the MAN pages or HTML created...even PDF, if you have a renderer installed (fop, xep or jw).

If you haven't already downloaded the documentation sources to your computer, please visit DeveloperGuide/Introduction now. It will give you pointers, and lead you through the steps of setting up a local repository. Then, you can find the documentation stuff in the folder doc at the top-level.


You need to have the Python binding for either libxml2 or lxml installed. For rendering PDF documents, you'll need a program like fop, xep or jw available in your system-wide $PATH. Creating the EPUB output files of the UserGuide and the MAN page, both depend on the Ghostscript executable gs for creating the front cover image. fop requires Java but is easily installed via apt-get on Debian/Ubuntu. jw is available for Debian/Ubuntu as part of the docbook-utils package. You'll also need epydoc in the python-epydoc package.


Just a few more words about the validation step. We are using our own DTD/XSD as a kind of hook, which only exists to link our own SCons documentation tags into the normal Docbook XSD. For the output, we always have an intermediary step (see diagram above), where we rewrite tags like cvar into a block of Docbook formatting elements representing it.

The toolchain, and all the Python scripts supporting it, are based on the prerequisite that all documents are valid against the SCons Docbook XSD. This step guarantees that we can accept the pull request of a user/writer with all his changes, and can create the documentation for a new release of SCons without any problems at a later time.


We are using entities for special keywords like SCons that should appear with the same formatting throughout the text. These are kept in a single file doc/scons.mod which gets included by the documents.

Additionally, for each Tool, Builder, Cvar and Function, a bunch of linkends in the form of entities get defined. They can be used in the MAN page and the User manual.

When you add an XML file in the src/engine/Tools folder, e.g. for a tool named foobar, you can use the two entities
which prints the name of the Tool, and
which is a link to the description of the Tool in the Appendix

of the User guide's text.

By calling the script

python bin/

you can recreate the lists of entities (*.mod) in the generated folder, if required. At the same time, this will generate the *.gen files, which list the full description of all the Builders, Tools, Functions and CVars for the MAN page and the guide's appendix.

For more information about how to properly describe these elements, refer to the start of the Python script bin/ It explains the available tags and the exact syntax in detail.


In the User Guide, we support automatically created examples. This means that the output of the specified source files and SConstructs, is generated by running them with the current SCons version. We do this to ensure that the output displayed in the manual, is identical to what you get when you run the example on the command-line.

A short description about how these examples have to be defined, can be found at the start of the file bin/ Call

python bin/

from the top level source folder, to run all examples through SCons.

Before this script starts to generate any output, it checks whether the names of all defined examples are unique. Another important prerequisite is, that for every example all the single scons_output blocks need to have a suffix attribute defined. These suffixes also have to be unique, within each example.

All example output files (*.xml) get written to the folder doc/generated/examples, together with all files defined via the scons_example_file tag. They are put under version control, too. Like this, it is easier to compare whether the output got broken for a new version of SCons.

Note, that these output files are not actually needed for editing the documents. When loading the User manual into an XML editor, you will always see the example's definition. Only when you create some output, the files from doc/generated/examples get XIncluded and all special scons* tags are transformed into Docbook elements.


Documents are in the folders design, developer, man, python10, reference, and user.
Prepared configuration sets for the validating WYSIWYG XML editors XmlMind and Serna. You'll probably want to try the latter, because the XXE config requires you to have a full version (costing a few hundred bucks) and is therefore untested. For installing the Serna config, simply copy the scons folder into the plugins directory of your installation. Likewise, the XXE files from the xmlmind folder have to be copied into ~/.xxe4/ under Linux.
Entity lists and outputs of the UserGuide examples. They get generated by the update scripts bin/ and bin/
Images for the overview.rst document.
The SCons Docbook schema (XSD), based on the Docbook v4.5 DTD/XSD.
XSLT transformation scripts for converting the special SCons tags like scons_output to valid Docbook during document processing.

Old toolchain

This is the documentation for SCons versions before 2.3.x; see also the discussion page for some points that got discussed and finally led to the new DocBook-based approach above.

Documentation sources for Docbook are maintained in doc/*/*.xml files. For the ones that require preprocessing to insert examples, the primary source files are doc/*/*.in. We have our own preprocessing stage to update and insert examples into XML sources before they are processed.

List of tools you'll need to build documentation

These package names can be passed directly to 'apt-get install' for Ubuntu or Debian.

  • python-epydoc
  • jade
  • openjade
  • tetex-bin
  • tetex-latex
  • texlive-latex-extra
  • jadetex ?
  • docbook
  • docbook-doc
  • docbook-dsssl
  • docbook-to-man
  • docbook-utils
  • docbook-xml
  • docbook-xsl
  • docbook2x
  • man2html

[GaryOberbrunner 15-Jul-12] As of Ubuntu 10.04, some of the above pkgs don't exist. These do: apt-get install python-epydoc jade openjade texinfo texlive-latex-extra jadetex docbook docbook-dsssl docbook-to-man docbook-utils docbook-xml docbook-xsl docbook2x man2html and the doc seems to build OK with those packages (and their dependencies).

Not strictly doc-related, but if you're doing release builds, you also need rpm if you're on a non-RedHat/CentOS machine: apt-get install rpm.

Steps to update or add content to the User Guide

  1. Edit the doc/user/
  2. python bin/ --diff file
  3. Review the diffs introduced by your changes, and proceed if they look correct
  4. python bin/ --update file
  5. python doc
  6. Review the generated documents in build/doc/html/scons-user.html (and .ps and .pdf)
  7. Submit patch for review

Future work

  1. Make documentation building process cross-platform
  2. Cut the amount of tools and dependencies (preferably to Python modules)

Behind the curtain

The following image depicts the single steps of a full build for the documentation. The first (and zeroth) column shows the required tools (= dependencies) for each section (= second column).