           FreeBSD Documentation Project Primer for New Contributors

  The FreeBSD Documentation Project

   Revision: 51563

   Copyright (c) 1998-2017 DocEng

   Copyright

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    1. Redistributions of source code (XML DocBook) must retain the above
       copyright notice, this list of conditions and the following disclaimer
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   Last modified on 2018-04-17 11:20:38 by mat.
   Abstract

   Thank you for becoming a part of the FreeBSD Documentation Project. Your
   contribution is extremely valuable, and we appreciate it.

   This primer covers details needed to start contributing to the FreeBSD
   Documentation Project, or FDP, including tools, software, and the
   philosophy behind the Documentation Project.

   This is a work in progress. Corrections and additions are always welcome.

   [ Split HTML / Single HTML ]

     ----------------------------------------------------------------------

   Table of Contents

   Preface

                1. Shell Prompts

                2. Typographic Conventions

                3. Notes, Tips, Important Information, Warnings, and Examples

                4. Acknowledgments

   1. Overview

                1.1. Quick Start

                1.2. The FreeBSD Documentation Set

   2. Tools

                2.1. Required Tools

                2.2. Optional Tools

   3. The Working Copy

                3.1. Documentation and Manual Pages

                3.2. Choosing a Directory

                3.3. Checking Out a Copy

                3.4. Updating a Working Copy

                3.5. Reverting Changes

                3.6. Making a Diff

                3.7. Subversion References

   4. Documentation Directory Structure

                4.1. The Top Level, doc/

                4.2. The lang.encoding/ Directories

                4.3. Document-Specific Information

   5. The Documentation Build Process

                5.1. Rendering DocBook into Output

                5.2. The FreeBSD Documentation Build Toolset

                5.3. Understanding Makefiles in the Documentation Tree

                5.4. FreeBSD Documentation Project Make Includes

   6. The Website

                6.1. Environment Variables

                6.2. Building and Installing the Web Pages

   7. XML Primer

                7.1. Overview

                7.2. Elements, Tags, and Attributes

                7.3. The DOCTYPE Declaration

                7.4. Escaping Back to XML

                7.5. Comments

                7.6. Entities

                7.7. Using Entities to Include Files

                7.8. Marked Sections

                7.9. Conclusion

   8. XHTML Markup

                8.1. Introduction

                8.2. Formal Public Identifier (FPI)

                8.3. Sectional Elements

                8.4. Block Elements

                8.5. In-line Elements

   9. DocBook Markup

                9.1. Introduction

                9.2. FreeBSD Extensions

                9.3. Formal Public Identifier (FPI)

                9.4. Document Structure

                9.5. Block Elements

                9.6. In-line Elements

                9.7. Images

                9.8. Links

   10. Style Sheets

                10.1. CSS

   11. Translations

   12. PO Translations

                12.1. Introduction

                12.2. Quick Start

                12.3. Creating New Translations

                12.4. Translating

                12.5. Tips for Translators

                12.6. Building a Translated Document

                12.7. Submitting the New Translation

   13. Manual Pages

                13.1. Introduction

                13.2. Sections

                13.3. Markup

                13.4. Sample Manual Page Structures

                13.5. Example Manual Pages to Use as Templates

                13.6. Resources

   14. Writing Style

                14.1. Tips

                14.2. Guidelines

                14.3. Style Guide

                14.4. Word List

   15. Editor Configuration

                15.1. Vim

                15.2. Emacs

                15.3. nano

   16. See Also

                16.1. The FreeBSD Documentation Project

                16.2. XML

                16.3. HTML

                16.4. DocBook

   A. Examples

                A.1. DocBook book

                A.2. DocBook article

   Index

   List of Tables

   5.1. Common Output Formats

   12.1. Language Names

   List of Examples

   1. A Sample Example

   5.1. Build a Single HTML Output File

   5.2. Build HTML-Split and PDF Output Files

   6.1. Build the Full Web Site and All Documents

   6.2. Build Only the Web Site in English

   6.3. Build and Install the Web Site

   7.1. Using an Element (Start and End Tags)

   7.2. Using an Element Without Content

   7.3. Elements Within Elements; em

   7.4. Using an Element with an Attribute

   7.5. Single Quotes Around Attributes

   7.6. XML Generic Comments

   7.7. Erroneous XML Comment

   7.8. Defining General Entities

   7.9. Defining Parameter Entities

   7.10. Using General Entities to Include Files

   7.11. Using Parameter Entities to Include Files

   7.12. Structure of a Marked Section

   7.13. Using a CDATA Marked Section

   7.14. Using INCLUDE and IGNORE in Marked Sections

   7.15. Using a Parameter Entity to Control a Marked Section

   8.1. Normal XHTML Document Structure

   8.2. h1, h2, and Other Header Tags

   8.3. p Example

   8.4. blockquote Example

   8.5. ul and ol Example

   8.6. Definition Lists with dl

   8.7. pre Example

   8.8. Simple Use of table

   8.9. Using rowspan

   8.10. Using colspan

   8.11. Using rowspan and colspan Together

   8.12. em and strong Example

   8.13. tt Example

   8.14. Using <a href="...">

   8.15. Creating an Anchor

   8.16. Linking to a Named Part of a Different Document

   8.17. Linking to a Named Part of the Same Document

   9.1. Boilerplate book with info

   9.2. Boilerplate article with info

   9.3. A Simple Chapter

   9.4. Empty Chapters

   9.5. Sections in Chapters

   9.6. para Example

   9.7. blockquote Example

   9.8. tip and important Example

   9.9. example Source

   9.10. Rendered example

   9.11. itemizedlist and orderedlist Example

   9.12. variablelist Example

   9.13. procedure Example

   9.14. programlisting Example

   9.15. co and calloutlist Example

   9.16. informaltable Example

   9.17. Table with frame="none" Example

   9.18. screen, prompt, and userinput Example

   9.19. emphasis Example

   9.20. acronym Example

   9.21. quote Example

   9.22. Keys, Mouse Buttons, and Combinations Example

   9.23. Applications, Commands, and Options Example

   9.24. filename Example

   9.25. package Example

   9.26. systemitem and Classes Example

   9.27. uri Example

   9.28. email with a Hyperlink Example

   9.29. email Without a Hyperlink Example

   9.30. buildtarget and varname Example

   9.31. literal Example

   9.32. replaceable Example

   9.33. guibutton Example

   9.34. errorname Example

   9.35. xml:id on Chapters and Sections Example

   9.36. xref Example

   9.37. link to a FreeBSD Documentation Web Page Example

   9.38. link to a FreeBSD Web Page Example

   9.39. link to an External Web Page Example

   12.1. Creating a Spanish Translation of the Porter's Handbook

   12.2. Creating a French Translation of the PGP Keys Article

   12.3. Translating the Porter's Handbook to Spanish

   12.4. Preserving XML Tags

   12.5. Building the Spanish Porter's Handbook

   12.6. Spanish Translation of the NanoBSD Article

   12.7. Korean UTF-8 Translation of the Explaining-BSD Article

   A.1. DocBook book

   A.2. DocBook article

                                    Preface

   Table of Contents

   1. Shell Prompts

   2. Typographic Conventions

   3. Notes, Tips, Important Information, Warnings, and Examples

   4. Acknowledgments

1. Shell Prompts

   This table shows the default system prompt and superuser prompt. The
   examples use these prompts to indicate which type of user is running the
   example.

                    User                                 Prompt               
   Normal user                             %                                  
   root                                    #                                  

2. Typographic Conventions

   This table describes the typographic conventions used in this book.

             Meaning                              Examples                    
   The names of commands.       Use ls -l to list all files.                  
   The names of files.          Edit .login.                                  
   On-screen computer output.   You have mail.                                
   What the user types,         % date +"The time is %H:%M"                   
   contrasted with on-screen    The time is 09:18                             
   computer output.             
   Manual page references.      Use su(1) to change user identity.            
   User and group names.        Only root can do this.                        
   Emphasis.                    The user must do this.                        
   Text that the user is        To search for a keyword in the manual pages,  
   expected to replace with the type man -k keyword                           
   actual text.                 
   Environment variables.       $HOME is set to the user's home directory.    

3. Notes, Tips, Important Information, Warnings, and Examples

   Notes, warnings, and examples appear within the text.

  Note:

   Notes are represented like this, and contain information to take note of,
   as it may affect what the user does.

  Tip:

   Tips are represented like this, and contain information helpful to the
   user, like showing an easier way to do something.

  Important:

   Important information is represented like this. Typically, these show
   extra steps the user may need to take.

  Warning:

   Warnings are represented like this, and contain information warning about
   possible damage if the instructions are not followed. This damage may be
   physical, to the hardware or the user, or it may be non-physical, such as
   the inadvertent deletion of important files.

   Example 1. A Sample Example

   Examples are represented like this, and typically contain examples showing
   a walkthrough, or the results of a particular action.

4. Acknowledgments

   My thanks to Sue Blake, Patrick Durusau, Jon Hamilton, Peter Flynn, and
   Christopher Maden, who took the time to read early drafts of this document
   and offer many valuable comments and criticisms.

                              Chapter 1. Overview

   Table of Contents

   1.1. Quick Start

   1.2. The FreeBSD Documentation Set

   Welcome to the FreeBSD Documentation Project (FDP). Quality documentation
   is crucial to the success of FreeBSD, and we value your contributions very
   highly.

   This document describes how the FDP is organized, how to write and submit
   documentation, and how to effectively use the available tools.

   Everyone is welcome to contribute to the FDP. Willingness to contribute is
   the only membership requirement.

   This primer shows how to:

     * Identify which parts of FreeBSD are maintained by the FDP.

     * Install the required documentation tools and files.

     * Make changes to the documentation.

     * Submit changes back for review and inclusion in the FreeBSD
       documentation.

1.1. Quick Start

   Some preparatory steps must be taken before editing the FreeBSD
   documentation. First, subscribe to the FreeBSD documentation project
   mailing list. Some team members also interact on the #bsddocs IRC channel
   on EFnet. These people can help with questions or problems involving the
   documentation.

    1. Install the textproc/docproj meta-package and Subversion. This
       meta-package installs all of the software needed to edit and build
       FreeBSD documentation. The Subversion package is needed to obtain a
       working copy of the documentation and generate patches with.

 # pkg install docproj subversion

    2. Install a local working copy of the documentation from the FreeBSD
       repository in ~/doc (see Chapter 3, The Working Copy).

 % svn checkout https://svn.FreeBSD.org/doc/head ~/doc

    3. Configure the text editor:

          * Word wrap set to 70 characters.

          * Tab stops set to 2.

          * Replace each group of 8 leading spaces with a single tab.

       Specific editor configurations are listed in Chapter 15, Editor
       Configuration.

    4. Update the local working copy:

 % svn up ~/doc

    5. Edit the documentation files that require changes. If a file needs
       major changes, consult the mailing list for input.

       References to tag and entity usage can be found in Chapter 8, XHTML
       Markup and Chapter 9, DocBook Markup.

    6. After editing, check for problems by running:

 % igor -R filename.xml | less -RS

       Review the output and edit the file to fix any problems shown, then
       rerun the command to find any remaining problems. Repeat until all of
       the errors are resolved.

    7. Always build-test changes before submitting them. Running make in the
       top-level directory of the documentation being edited will generate
       that documentation in split HTML format. For example, to build the
       English version of the Handbook in HTML, run make in the
       en_US.ISO8859-1/books/handbook/ directory.

    8. When changes are complete and tested, generate a "diff file":

 % cd ~/doc
 % svn diff > bsdinstall.diff.txt

       Give the diff file a descriptive name. In the example above, changes
       have been made to the bsdinstall portion of the Handbook.

    9. Submit the diff file using the web-based Problem Report system. If
       using the web form, enter a Summary of [patch] short description of
       problem. Select the Component Documentation. In the Description field,
       enter a short description of the changes and any important details
       about them. Use the [ Add an attachment ] button to attach the diff
       file. Finally, use the [ Submit Bug ] button to submit your diff to
       the problem report system.

1.2. The FreeBSD Documentation Set

   The FDP is responsible for four categories of FreeBSD documentation.

     * Handbook: The Handbook is the comprehensive online resource and
       reference for FreeBSD users.

     * FAQ: The FAQ uses a short question and answer format to address
       questions that are frequently asked on the various mailing lists and
       forums devoted to FreeBSD. This format does not permit long and
       comprehensive answers.

     * Manual pages: The English language system manual pages are usually not
       written by the FDP, as they are part of the base system. However, the
       FDP can reword parts of existing manual pages to make them clearer or
       to correct inaccuracies.

     * Web site: This is the main FreeBSD presence on the web, visible at
       https://www.FreeBSD.org/ and many mirrors around the world. The web
       site is typically a new user's first exposure to FreeBSD.

   Translation teams are responsible for translating the Handbook and web
   site into different languages. Manual pages are not translated at present.

   Documentation source for the FreeBSD web site, Handbook, and FAQ is
   available in the documentation repository at https://svn.FreeBSD.org/doc/.

   Source for manual pages is available in a separate source repository
   located at https://svn.FreeBSD.org/base/.

   Documentation commit messages are visible with svn log. Commit messages
   are also archived at
   http://lists.FreeBSD.org/mailman/listinfo/svn-doc-all.

   Web frontends to both of these repositories are available at
   https://svnweb.FreeBSD.org/doc/ and https://svnweb.FreeBSD.org/base/.

   Many people have written tutorials or how-to articles about FreeBSD. Some
   are stored as part of the FDP files. In other cases, the author has
   decided to keep the documentation separate. The FDP endeavors to provide
   links to as much of this external documentation as possible.

                                Chapter 2. Tools

   Table of Contents

   2.1. Required Tools

   2.2. Optional Tools

   Several software tools are used to manage the FreeBSD documentation and
   render it to different output formats. Some of these tools are required
   and must be installed before working through the examples in the following
   chapters. Some are optional, adding capabilities or making the job of
   creating documentation less demanding.

2.1. Required Tools

   Install textproc/docproj from the Ports Collection. This meta-port
   installs all the applications required to do useful work with the FreeBSD
   documentation. Some further notes on particular components are given
   below.

  2.1.1. DTDs and Entities

   FreeBSD documentation uses several Document Type Definitions (DTDs) and
   sets of XML entities. These are all installed by the textproc/docproj
   port.

   XHTML DTD (textproc/xhtml)

           XHTML is the markup language of choice for the World Wide Web, and
           is used throughout the FreeBSD web site.

   DocBook DTD (textproc/docbook-xml)

           DocBook is designed for marking up technical documentation. Most
           of the FreeBSD documentation is written in DocBook.

   ISO 8879 entities (textproc/iso8879)

           Character entities from the ISO 8879:1986 standard used by many
           DTDs. Includes named mathematical symbols, additional characters
           in the Latin character set (accents, diacriticals, and so on), and
           Greek symbols.

2.2. Optional Tools

   These applications are not required, but can make working on the
   documentation easier or add capabilities.

  2.2.1. Software

   Vim (editors/vim)

           A popular editor for working with XML and derived documents, like
           DocBook XML.

   Emacs or XEmacs (editors/emacs or editors/xemacs)

           Both of these editors include a special mode for editing documents
           marked up according to an XML DTD. This mode includes commands to
           reduce the amount of typing needed, and help reduce the
           possibility of errors.

                          Chapter 3. The Working Copy

   Table of Contents

   3.1. Documentation and Manual Pages

   3.2. Choosing a Directory

   3.3. Checking Out a Copy

   3.4. Updating a Working Copy

   3.5. Reverting Changes

   3.6. Making a Diff

   3.7. Subversion References

   The working copy is a copy of the FreeBSD repository documentation tree
   downloaded onto the local computer. Changes are made to the local working
   copy, tested, and then submitted as patches to be committed to the main
   repository.

   A full copy of the documentation tree can occupy 700 megabytes of disk
   space. Allow for a full gigabyte of space to have room for temporary files
   and test versions of various output formats.

   Subversion is used to manage the FreeBSD documentation files. It is
   obtained by installing the Subversion package:

 # pkg install subversion

3.1. Documentation and Manual Pages

   FreeBSD documentation is not just books and articles. Manual pages for all
   the commands and configuration files are also part of the documentation,
   and part of the FDP's territory. Two repositories are involved: doc for
   the books and articles, and base for the operating system and manual
   pages. To edit manual pages, the base repository must be checked out
   separately.

   Repositories may contain multiple versions of documentation and source
   code. New modifications are almost always made only to the latest version,
   called head.

3.2. Choosing a Directory

   FreeBSD documentation is traditionally stored in /usr/doc/, and system
   source code with manual pages in /usr/src/. These directory trees are
   relocatable, and users may want to put the working copies in other
   locations to avoid interfering with existing information in the main
   directories. The examples that follow use ~/doc and ~/src, both
   subdirectories of the user's home directory.

3.3. Checking Out a Copy

   A download of a working copy from the repository is called a checkout, and
   done with svn checkout. This example checks out a copy of the latest
   version (head) of the main documentation tree:

 % svn checkout https://svn.FreeBSD.org/doc/head ~/doc

   A checkout of the source code to work on manual pages is very similar:

 % svn checkout https://svn.FreeBSD.org/base/head ~/src

3.4. Updating a Working Copy

   The documents and files in the FreeBSD repository change daily. People
   modify files and commit changes frequently. Even a short time after an
   initial checkout, there will already be differences between the local
   working copy and the main FreeBSD repository. To update the local version
   with the changes that have been made to the main repository, use svn
   update on the directory containing the local working copy:

 % svn update ~/doc

   Get in the protective habit of using svn update before editing document
   files. Someone else may have edited that file very recently, and the local
   working copy will not include the latest changes until it has been
   updated. Editing the newest version of a file is much easier than trying
   to combine an older, edited local file with the newer version from the
   repository.

3.5. Reverting Changes

   Sometimes it turns out that changes were not necessary after all, or the
   writer just wants to start over. Files can be "reset" to their unchanged
   form with svn revert. For example, to erase the edits made to chapter.xml
   and reset it to unmodified form:

 % svn revert chapter.xml

3.6. Making a Diff

   After edits to a file or group of files are completed, the differences
   between the local working copy and the version on the FreeBSD repository
   must be collected into a single file for submission. These diff files are
   produced by redirecting the output of svn diff into a file:

 % cd ~/doc
 % svn diff > doc-fix-spelling.diff

   Give the file a meaningful name that identifies the contents. The example
   above is for spelling fixes to the whole documentation tree.

   If the diff file is to be submitted with the web "Submit a FreeBSD problem
   report" interface, add a .txt extension to give the earnest and
   simple-minded web form a clue that the contents are plain text.

   Be careful: svn diff includes all changes made in the current directory
   and any subdirectories. If there are files in the working copy with edits
   that are not ready to be submitted yet, provide a list of only the files
   that are to be included:

 % cd ~/doc
 % svn diff disks/chapter.xml printers/chapter.xml > disks-printers.diff

3.7. Subversion References

   These examples show very basic usage of Subversion. More detail is
   available in the Subversion Book and the Subversion documentation.

                  Chapter 4. Documentation Directory Structure

   Table of Contents

   4.1. The Top Level, doc/

   4.2. The lang.encoding/ Directories

   4.3. Document-Specific Information

   Files and directories in the doc/ tree follow a structure meant to:

    1. Make it easy to automate converting the document to other formats.

    2. Promote consistency between the different documentation organizations,
       to make it easier to switch between working on different documents.

    3. Make it easy to decide where in the tree new documentation should be
       placed.

   In addition, the documentation tree must accommodate documents in many
   different languages and encodings. It is important that the documentation
   tree structure does not enforce any particular defaults or cultural
   preferences.

4.1. The Top Level, doc/

   There are two types of directory under doc/, each with very specific
   directory names and meanings.

     Directory                              Usage                             
   share         Contains files that are not specific to the various          
                 translations and encodings of the documentation. Contains    
                 subdirectories to further categorize the information. For    
                 example, the files that comprise the make(1) infrastructure  
                 are in share/mk, while the additional XML support files      
                 (such as the FreeBSD extended DocBook DTD) are in share/xml. 
   lang.encoding One directory exists for each available translation and      
                 encoding of the documentation, for example en_US.ISO8859-1/  
                 and zh_TW.UTF-8/. The names are long, but by fully           
                 specifying the language and encoding we prevent any future   
                 headaches when a translation team wants to provide           
                 documentation in the same language but in more than one      
                 encoding. This also avoids problems that might be caused by  
                 a future switch to Unicode.                                  

4.2. The lang.encoding/ Directories

   These directories contain the documents themselves. The documentation is
   split into up to three more categories at this level, indicated by the
   different directory names.

   Directory                              Usage                               
   articles  Documentation marked up as a DocBook article (or equivalent).    
             Reasonably short, and broken up into sections. Normally only     
             available as one XHTML file.                                     
   books     Documentation marked up as a DocBook book (or equivalent). Book  
             length, and broken up into chapters. Normally available as both  
             one large XHTML file (for people with fast connections, or who   
             want to print it easily from a browser) and as a collection of   
             linked, smaller files.                                           
   man       For translations of the system manual pages. This directory will 
             contain one or more manN directories, corresponding to the       
             sections that have been translated.                              

   Not every lang.encoding directory will have all of these subdirectories.
   It depends on how much translation has been accomplished by that
   translation team.

4.3. Document-Specific Information

   This section contains specific notes about particular documents managed by
   the FDP.

  4.3.1. The Handbook

    books/handbook/

   The Handbook is written in DocBook XML using the FreeBSD DocBook extended
   DTD.

   The Handbook is organized as a DocBook book. The book is divided into
   parts, each of which contains several chapters. chapters are further
   subdivided into sections (sect1) and subsections (sect2, sect3) and so on.

    4.3.1.1. Physical Organization

   There are a number of files and directories within the handbook directory.

  Note:

   The Handbook's organization may change over time, and this document may
   lag in detailing the organizational changes. Post questions about Handbook
   organization to the FreeBSD documentation project mailing list.

      4.3.1.1.1. Makefile

   The Makefile defines some variables that affect how the XML source is
   converted to other formats, and lists the various source files that make
   up the Handbook. It then includes the standard doc.project.mk, to bring in
   the rest of the code that handles converting documents from one format to
   another.

      4.3.1.1.2. book.xml

   This is the top level document in the Handbook. It contains the Handbook's
   DOCTYPE declaration, as well as the elements that describe the Handbook's
   structure.

   book.xml uses parameter entities to load in the files with the .ent
   extension. These files (described later) then define general entities that
   are used throughout the rest of the Handbook.

      4.3.1.1.3. directory/chapter.xml

   Each chapter in the Handbook is stored in a file called chapter.xml in a
   separate directory from the other chapters. Each directory is named after
   the value of the id attribute on the chapter element.

   For example, if one of the chapter files contains:

 <chapter id="kernelconfig">
 ...
 </chapter>

   Then it will be called chapter.xml in the kernelconfig directory. In
   general, the entire contents of the chapter are in this one file.

   When the XHTML version of the Handbook is produced, this will yield
   kernelconfig.html. This is because of the id value, and is not related to
   the name of the directory.

   In earlier versions of the Handbook, the files were stored in the same
   directory as book.xml, and named after the value of the id attribute on
   the file's chapter element. Now, it is possible to include images in each
   chapter. Images for each Handbook chapter are stored within
   share/images/books/handbook. The localized version of these images should
   be placed in the same directory as the XML sources for each chapter.
   Namespace collisions are inevitable, and it is easier to work with several
   directories with a few files in them than it is to work with one directory
   that has many files in it.

   A brief look will show that there are many directories with individual
   chapter.xml files, including basics/chapter.xml, introduction/chapter.xml,
   and printing/chapter.xml.

  Important:

   Do not name chapters or directories after their ordering within the
   Handbook. This ordering can change as the content within the Handbook is
   reorganized. Reorganization should be possible without renaming files,
   unless entire chapters are being promoted or demoted within the hierarchy.

   The chapter.xml files are not complete XML documents that can be built
   individually. They can only be built as parts of the whole Handbook.

                   Chapter 5. The Documentation Build Process

   Table of Contents

   5.1. Rendering DocBook into Output

   5.2. The FreeBSD Documentation Build Toolset

   5.3. Understanding Makefiles in the Documentation Tree

   5.4. FreeBSD Documentation Project Make Includes

   This chapter covers organization of the documentation build process and
   how make(1) is used to control it.

5.1. Rendering DocBook into Output

   Different types of output can be produced from a single DocBook source
   file. The type of output desired is set with the FORMATS variable. A list
   of known formats is stored in KNOWN_FORMATS:

 % cd ~/doc/en_US.ISO8859-1/books/handbook
 % make -V KNOWN_FORMATS

   Table 5.1. Common Output Formats

   FORMATS Value      File Type                     Description               
   html          HTML, one file       A single book.html or article.html.     
                                      Multiple HTML files, one for each       
   html-split    HTML, multiple files chapter or section, for use on a        
                                      typical web site.                       
   pdf           PDF                  Portable Document Format                

   The default output format can vary by document, but is usually html-split.
   Other formats are chosen by setting FORMATS to a specific value. Multiple
   output formats can be created at a single time by setting FORMATS to a
   list of formats.

   Example 5.1. Build a Single HTML Output File

 % cd ~/doc/en_US.ISO8859-1/books/handbook
 % make FORMATS=html

   Example 5.2. Build HTML-Split and PDF Output Files

 % cd ~/doc/en_US.ISO8859-1/books/handbook
 % make FORMATS="html-split pdf"

5.2. The FreeBSD Documentation Build Toolset

   These are the tools used to build and install the FDP documentation.

     * The primary build tool is make(1), specifically Berkeley Make.

     * Package building is handled by FreeBSD's pkg-create(8).

     * gzip(1) is used to create compressed versions of the document.
       bzip2(1) archives are also supported. tar(1) is used for package
       building.

     * install(1) is used to install the documentation.

5.3. Understanding Makefiles in the Documentation Tree

   There are three main types of Makefiles in the FreeBSD Documentation
   Project tree.

     * Subdirectory Makefiles simply pass commands to those directories below
       them.

     * Documentation Makefiles describe the documents that are produced from
       this directory.

     * Make includes are the glue that perform the document production, and
       are usually of the form doc.xxx.mk.

  5.3.1. Subdirectory Makefiles

   These Makefiles usually take the form of:

 SUBDIR =articles
 SUBDIR+=books

 COMPAT_SYMLINK = en

 DOC_PREFIX?= ${.CURDIR}/..
 .include "${DOC_PREFIX}/share/mk/doc.project.mk"

   The first four non-empty lines define the make(1) variables SUBDIR,
   COMPAT_SYMLINK, and DOC_PREFIX.

   The SUBDIR statement and COMPAT_SYMLINK statement show how to assign a
   value to a variable, overriding any previous value.

   The second SUBDIR statement shows how a value is appended to the current
   value of a variable. The SUBDIR variable is now articles books.

   The DOC_PREFIX assignment shows how a value is assigned to the variable,
   but only if it is not already defined. This is useful if DOC_PREFIX is not
   where this Makefile thinks it is - the user can override this and provide
   the correct value.

   What does it all mean? SUBDIR mentions which subdirectories below this one
   the build process should pass any work on to.

   COMPAT_SYMLINK is specific to compatibility symlinks (amazingly enough)
   for languages to their official encoding (doc/en would point to
   en_US.ISO-8859-1).

   DOC_PREFIX is the path to the root of the FreeBSD Document Project tree.
   This is not always that easy to find, and is also easily overridden, to
   allow for flexibility. .CURDIR is a make(1) builtin variable with the path
   to the current directory.

   The final line includes the FreeBSD Documentation Project's project-wide
   make(1) system file doc.project.mk which is the glue which converts these
   variables into build instructions.

  5.3.2. Documentation Makefiles

   These Makefiles set make(1) variables that describe how to build the
   documentation contained in that directory.

   Here is an example:

 MAINTAINER=nik@FreeBSD.org

 DOC?= book

 FORMATS?= html-split html

 INSTALL_COMPRESSED?= gz
 INSTALL_ONLY_COMPRESSED?=

 # SGML content
 SRCS=  book.xml

 DOC_PREFIX?= ${.CURDIR}/../../..

 .include "$(DOC_PREFIX)/share/mk/docproj.docbook.mk"

   The MAINTAINER variable allows committers to claim ownership of a document
   in the FreeBSD Documentation Project, and take responsibility for
   maintaining it.

   DOC is the name (sans the .xml extension) of the main document created by
   this directory. SRCS lists all the individual files that make up the
   document. This should also include important files in which a change
   should result in a rebuild.

   FORMATS indicates the default formats that should be built for this
   document. INSTALL_COMPRESSED is the default list of compression techniques
   that should be used in the document build. INSTALL_ONLY_COMPRESS, empty by
   default, should be non-empty if only compressed documents are desired in
   the build.

   The DOC_PREFIX and include statements should be familiar already.

5.4. FreeBSD Documentation Project Make Includes

   make(1) includes are best explained by inspection of the code. Here are
   the system include files:

     * doc.project.mk is the main project include file, which includes all
       the following include files, as necessary.

     * doc.subdir.mk handles traversing of the document tree during the build
       and install processes.

     * doc.install.mk provides variables that affect ownership and
       installation of documents.

     * doc.docbook.mk is included if DOCFORMAT is docbook and DOC is set.

  5.4.1. doc.project.mk

   By inspection:

 DOCFORMAT?=     docbook
 MAINTAINER?=    doc@FreeBSD.org

 PREFIX?=        /usr/local
 PRI_LANG?=      en_US.ISO8859-1

 .if defined(DOC)
 .if ${DOCFORMAT} == "docbook"
 .include "doc.docbook.mk"
 .endif
 .endif

 .include "doc.subdir.mk"
 .include "doc.install.mk"

    5.4.1.1. Variables

   DOCFORMAT and MAINTAINER are assigned default values, if these are not set
   by the document make file.

   PREFIX is the prefix under which the documentation building tools are
   installed. For normal package and port installation, this is /usr/local.

   PRI_LANG should be set to whatever language and encoding is natural
   amongst users these documents are being built for. US English is the
   default.

  Note:

   PRI_LANG does not affect which documents can, or even will, be built. Its
   main use is creating links to commonly referenced documents into the
   FreeBSD documentation install root.

    5.4.1.2. Conditionals

   The .if defined(DOC) line is an example of a make(1) conditional which,
   like in other programs, defines behavior if some condition is true or if
   it is false. defined is a function which returns whether the variable
   given is defined or not.

   .if ${DOCFORMAT} == "docbook", next, tests whether the DOCFORMAT variable
   is "docbook", and in this case, includes doc.docbook.mk.

   The two .endifs close the two above conditionals, marking the end of their
   application.

  5.4.2. doc.subdir.mk

   This file is too long to explain in detail. These notes describe the most
   important features.

    5.4.2.1. Variables

     * SUBDIR is a list of subdirectories that the build process should go
       further down into.

     * ROOT_SYMLINKS is the name of directories that should be linked to the
       document install root from their actual locations, if the current
       language is the primary language (specified by PRI_LANG).

     * COMPAT_SYMLINK is described in the Subdirectory Makefile section.

    5.4.2.2. Targets and Macros

   Dependencies are described by target: dependency1 dependency2 ... tuples,
   where to build target, the given dependencies must be built first.

   After that descriptive tuple, instructions on how to build the target may
   be given, if the conversion process between the target and its
   dependencies are not previously defined, or if this particular conversion
   is not the same as the default conversion method.

   A special dependency .USE defines the equivalent of a macro.

 _SUBDIRUSE: .USE
 .for entry in ${SUBDIR}
         @${ECHO} "===> ${DIRPRFX}${entry}"
         @(cd ${.CURDIR}/${entry} && \
         ${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
 .endfor

   In the above, _SUBDIRUSE is now a macro which will execute the given
   commands when it is listed as a dependency.

   What sets this macro apart from other targets? Basically, it is executed
   after the instructions given in the build procedure it is listed as a
   dependency to, and it does not adjust .TARGET, which is the variable which
   contains the name of the target currently being built.

 clean: _SUBDIRUSE
         rm -f ${CLEANFILES}

   In the above, clean will use the _SUBDIRUSE macro after it has executed
   the instruction rm -f ${CLEANFILES}. In effect, this causes clean to go
   further and further down the directory tree, deleting built files as it
   goes down, not on the way back up.

      5.4.2.2.1. Provided Targets

     * install and package both go down the directory tree calling the real
       versions of themselves in the subdirectories (realinstall and
       realpackage respectively).

     * clean removes files created by the build process (and goes down the
       directory tree too). cleandir does the same, and also removes the
       object directory, if any.

    5.4.2.3. More on Conditionals

     * exists is another condition function which returns true if the given
       file exists.

     * empty returns true if the given variable is empty.

     * target returns true if the given target does not already exist.

    5.4.2.4. Looping Constructs in make (.for)

   .for provides a way to repeat a set of instructions for each
   space-separated element in a variable. It does this by assigning a
   variable to contain the current element in the list being examined.

 _SUBDIRUSE: .USE
 .for entry in ${SUBDIR}
         @${ECHO} "===> ${DIRPRFX}${entry}"
         @(cd ${.CURDIR}/${entry} && \
         ${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
 .endfor

   In the above, if SUBDIR is empty, no action is taken; if it has one or
   more elements, the instructions between .for and .endfor would repeat for
   every element, with entry being replaced with the value of the current
   element.

                             Chapter 6. The Website

   Table of Contents

   6.1. Environment Variables

   6.2. Building and Installing the Web Pages

   The FreeBSD web site is part of the FreeBSD documents. Files for the web
   site are stored in the en_US.ISO8859-1/htdocs subdirectory of the document
   tree directory, ~/doc in this example.

6.1. Environment Variables

   Several environment variables control which parts of the web site are
   built or installed, and to which directories.

  Tip:

   The web build system uses make(1), and considers variables to be set when
   they have been defined, even if they are empty. The examples here show the
   recommended ways of defining and using these variables. Setting or
   defining these variables with other values or methods might lead to
   unexpected surprises.

   DESTDIR

           DESTDIR specifies the path where the web site files are to be
           installed.

           This variable is best set with env(1) or the user shell's method
           of setting environment variables, setenv for csh(1) or export for
           sh(1).

   ENGLISH_ONLY

           Default: undefined. Build and include all translations.

           ENGLISH_ONLY=yes: use only the English documents and ignore all
           translations.

   WEB_ONLY

           Default: undefined. Build both the web site and all the books and
           articles.

           WEB_ONLY=yes: build or install only HTML pages from the
           en_US.ISO8859-1/htdocs directory. Other directories and documents,
           including books and articles, will be ignored.

   WEB_LANG

           Default: undefined. Build and include all the available languages
           on the web site.

           Set to a space-separated list of languages to be included in the
           build or install. The formats are the same as the directory names
           in the document root directory. For example, to include the German
           and French documents:

 WEB_LANG="de_DE.ISO8859-1 fr_FR.ISO8859-1"

   WEB_ONLY, WEB_LANG, and ENGLISH_ONLY are make(1) variables and can be set
   in /etc/make.conf, Makefile.inc, as environment variables on the command
   line, or in dot files.

6.2. Building and Installing the Web Pages

   Having obtained the documentation and web site source files, the web site
   can be built.

   An actual installation of the web site is run as the root user because the
   permissions on the web server directory will not allow files to be
   installed by an unprivileged user. For testing, it can be useful to
   install the files as a normal user to a temporary directory.

   In these examples, the web site files are built by user jru in their home
   directory, ~/doc, with a full path of /usr/home/jru/doc.

  Tip:

   The web site build uses the INDEX from the Ports Collection and might fail
   if that file or /usr/ports is not present. The simplest approach is to
   install the Ports Collection.

   Example 6.1. Build the Full Web Site and All Documents

   Build the web site and all documents. The resulting files are left in the
   document tree:

 % cd ~/doc/en_US.ISO8859-1/htdocs/
 % make all

   Example 6.2. Build Only the Web Site in English

   Build the web site only, in English, as user jru, and install the
   resulting files into /tmp/www for testing:

 % cd ~/doc/en_US.ISO8859-1/htdocs/
 % env DESTDIR=/tmp/www make ENGLISH_ONLY=yes WEB_ONLY=yes all install

   Changes to static files can usually be tested by viewing the modified
   files directly with a web browser. If the site has been built as shown
   above, a modified main page can be viewed with:

 % firefox /tmp/www/data/index.html

   Modifications to dynamic files can be tested with a web server running on
   the local system. After building the site as shown above, this
   /usr/local/etc/apache24/httpd.conf can be used with www/apache24:

 # httpd.conf for testing the FreeBSD website
 Define TestRoot "/tmp/www/data"

 # directory for configuration files
 ServerRoot "/usr/local"

 Listen 80

 # minimum required modules
 LoadModule authz_core_module libexec/apache24/mod_authz_core.so
 LoadModule mime_module libexec/apache24/mod_mime.so
 LoadModule unixd_module libexec/apache24/mod_unixd.so
 LoadModule cgi_module libexec/apache24/mod_cgi.so
 LoadModule dir_module libexec/apache24/mod_dir.so

 # run the webserver as user and group
 User www
 Group www

 ServerAdmin you@example.com
 ServerName fbsdtest

 # deny access to all files
 <Directory />
     AllowOverride none
     Require all denied
 </Directory>

 # allow access to the website directory
 DocumentRoot "${TestRoot}"
 <Directory "${TestRoot}">
     Options Indexes FollowSymLinks
     AllowOverride None
     Require all granted
 </Directory>

 # prevent access to .htaccess and .htpasswd files
 <Files ".ht*">
     Require all denied
 </Files>

 ErrorLog "/var/log/httpd-error.log"
 LogLevel warn

 # set up the CGI script directory
 <Directory "${TestRoot}/cgi">
     AllowOverride None
     Options None
     Require all granted
     Options +ExecCGI
     AddHandler cgi-script .cgi
 </Directory>

 Include etc/apache24/Includes/*.conf

   Start the web server with

 # service apache24 onestart

   The web site can be viewed at http://localhost. Be aware that many links
   refer to the real FreeBSD site by name, and those links will still go to
   the external site instead of the local test version. Fully testing the
   local site will require temporarily setting DNS so www.FreeBSD.org
   resolves to localhost or the local IP address.

   Example 6.3. Build and Install the Web Site

   Build the web site and all documents as user jru. Install the resulting
   files as root into the default directory, /root/public_html:

 % cd ~/doc/en_US.ISO8859-1/htdocs
 % make all
 % su -
 Password:
 # cd /usr/home/jru/doc/en_US.ISO8859-1/htdocs
 # make install

   The install process does not delete any old or outdated files that existed
   previously in the same directory. If a new copy of the site is built and
   installed every day, this command will find and delete all files that have
   not been updated in three days:

 # find /usr/local/www -ctime 3 -delete

                             Chapter 7. XML Primer

   Table of Contents

   7.1. Overview

   7.2. Elements, Tags, and Attributes

   7.3. The DOCTYPE Declaration

   7.4. Escaping Back to XML

   7.5. Comments

   7.6. Entities

   7.7. Using Entities to Include Files

   7.8. Marked Sections

   7.9. Conclusion

   Most FDP documentation is written with markup languages based on XML. This
   chapter explains what that means, how to read and understand the
   documentation source, and the XML techniques used.

   Portions of this section were inspired by Mark Galassi's Get Going With
   DocBook.

7.1. Overview

   In the original days of computers, electronic text was simple. There were
   a few character sets like ASCII or EBCDIC, but that was about it. Text was
   text, and what you saw really was what you got. No frills, no formatting,
   no intelligence.

   Inevitably, this was not enough. When text is in a machine-usable format,
   machines are expected to be able to use and manipulate it intelligently.
   Authors want to indicate that certain phrases should be emphasized, or
   added to a glossary, or made into hyperlinks. Filenames could be shown in
   a "typewriter" style font for viewing on screen, but as "italics" when
   printed, or any of a myriad of other options for presentation.

   It was once hoped that Artificial Intelligence (AI) would make this easy.
   The computer would read the document and automatically identify key
   phrases, filenames, text that the reader should type in, examples, and
   more. Unfortunately, real life has not happened quite like that, and
   computers still require assistance before they can meaningfully process
   text.

   More precisely, they need help identifying what is what. Consider this
   text:

     To remove /tmp/foo, use rm(1).

 % rm /tmp/foo

   It is easy to see which parts are filenames, which are commands to be
   typed in, which parts are references to manual pages, and so on. But the
   computer processing the document cannot. For this we need markup.

   "Markup" is commonly used to describe "adding value" or "increasing cost".
   The term takes on both these meanings when applied to text. Markup is
   additional text included in the document, distinguished from the
   document's content in some way, so that programs that process the document
   can read the markup and use it when making decisions about the document.
   Editors can hide the markup from the user, so the user is not distracted
   by it.

   The extra information stored in the markup adds value to the document.
   Adding the markup to the document must typically be done by a person-after
   all, if computers could recognize the text sufficiently well to add the
   markup then there would be no need to add it in the first place. This
   increases the cost (the effort required) to create the document.

   The previous example is actually represented in this document like this:

 <para>To remove <filename>/tmp/foo</filename>, use &man.rm.1;.</para>

 <screen>&prompt.user; <userinput>rm /tmp/foo</userinput></screen>

   The markup is clearly separate from the content.

   Markup languages define what the markup means and how it should be
   interpreted.

   Of course, one markup language might not be enough. A markup language for
   technical documentation has very different requirements than a markup
   language that is intended for cookery recipes. This, in turn, would be
   very different from a markup language used to describe poetry. What is
   really needed is a first language used to write these other markup
   languages. A meta markup language.

   This is exactly what the eXtensible Markup Language (XML) is. Many markup
   languages have been written in XML, including the two most used by the
   FDP, XHTML and DocBook.

   Each language definition is more properly called a grammar, vocabulary,
   schema or Document Type Definition (DTD). There are various languages to
   specify an XML grammar, or schema.

   A schema is a complete specification of all the elements that are allowed
   to appear, the order in which they should appear, which elements are
   mandatory, which are optional, and so forth. This makes it possible to
   write an XML parser which reads in both the schema and a document which
   claims to conform to the schema. The parser can then confirm whether or
   not all the elements required by the vocabulary are in the document in the
   right order, and whether there are any errors in the markup. This is
   normally referred to as "validating the document".

  Note:

   Validation confirms that the choice of elements, their ordering, and so
   on, conforms to that listed in the grammar. It does not check whether
   appropriate markup has been used for the content. If all the filenames in
   a document were marked up as function names, the parser would not flag
   this as an error (assuming, of course, that the schema defines elements
   for filenames and functions, and that they are allowed to appear in the
   same place).

   Most contributions to the Documentation Project will be content marked up
   in either XHTML or DocBook, rather than alterations to the schemas. For
   this reason, this book will not touch on how to write a vocabulary.

7.2. Elements, Tags, and Attributes

   All the vocabularies written in XML share certain characteristics. This is
   hardly surprising, as the philosophy behind XML will inevitably show
   through. One of the most obvious manifestations of this philosophy is that
   of content and elements.

   Documentation, whether it is a single web page, or a lengthy book, is
   considered to consist of content. This content is then divided and further
   subdivided into elements. The purpose of adding markup is to name and
   identify the boundaries of these elements for further processing.

   For example, consider a typical book. At the very top level, the book is
   itself an element. This "book" element obviously contains chapters, which
   can be considered to be elements in their own right. Each chapter will
   contain more elements, such as paragraphs, quotations, and footnotes. Each
   paragraph might contain further elements, identifying content that was
   direct speech, or the name of a character in the story.

   It may be helpful to think of this as "chunking" content. At the very top
   level is one chunk, the book. Look a little deeper, and there are more
   chunks, the individual chapters. These are chunked further into
   paragraphs, footnotes, character names, and so on.

   Notice how this differentiation between different elements of the content
   can be made without resorting to any XML terms. It really is surprisingly
   straightforward. This could be done with a highlighter pen and a printout
   of the book, using different colors to indicate different chunks of
   content.

   Of course, we do not have an electronic highlighter pen, so we need some
   other way of indicating which element each piece of content belongs to. In
   languages written in XML (XHTML, DocBook, et al) this is done by means of
   tags.

   A tag is used to identify where a particular element starts, and where the
   element ends. The tag is not part of the element itself. Because each
   grammar was normally written to mark up specific types of information,
   each one will recognize different elements, and will therefore have
   different names for the tags.

   For an element called element-name the start tag will normally look like
   <element-name>. The corresponding closing tag for this element is
   </element-name>.

   Example 7.1. Using an Element (Start and End Tags)

   XHTML has an element for indicating that the content enclosed by the
   element is a paragraph, called p.

 <p>This is a paragraph.  It starts with the start tag for
   the 'p' element, and it will end with the end tag for the 'p'
   element.</p>

 <p>This is another paragraph.  But this one is much shorter.</p>

   Some elements have no content. For example, in XHTML, a horizontal line
   can be included in the document. For these "empty" elements, XML
   introduced a shorthand form that is completely equivalent to the two-tag
   version:

   Example 7.2. Using an Element Without Content

   XHTML has an element for indicating a horizontal rule, called hr. This
   element does not wrap content, so it looks like this:

 <p>One paragraph.</p>
 <hr></hr>

 <p>This is another paragraph.  A horizontal rule separates this
   from the previous paragraph.</p>

   The shorthand version consists of a single tag:

 <p>One paragraph.</p>
 <hr/>

 <p>This is another paragraph.  A horizontal rule separates this
   from the previous paragraph.</p>

   As shown above, elements can contain other elements. In the book example
   earlier, the book element contained all the chapter elements, which in
   turn contained all the paragraph elements, and so on.

   Example 7.3. Elements Within Elements; em

 <p>This is a simple <em>paragraph</em> where some
   of the <em>words</em> have been <em>emphasized</em>.</p>

   The grammar consists of rules that describe which elements can contain
   other elements, and exactly what they can contain.

  Important:

   People often confuse the terms tags and elements, and use the terms as if
   they were interchangeable. They are not.

   An element is a conceptual part of your document. An element has a defined
   start and end. The tags mark where the element starts and ends.

   When this document (or anyone else knowledgeable about XML) refers to "the
   <p> tag" they mean the literal text consisting of the three characters <,
   p, and >. But the phrase "the p element" refers to the whole element.

   This distinction is very subtle. But keep it in mind.

   Elements can have attributes. An attribute has a name and a value, and is
   used for adding extra information to the element. This might be
   information that indicates how the content should be rendered, or might be
   something that uniquely identifies that occurrence of the element, or it
   might be something else.

   An element's attributes are written inside the start tag for that element,
   and take the form attribute-name="attribute-value".

   In XHTML, the p element has an attribute called align, which suggests an
   alignment (justification) for the paragraph to the program displaying the
   XHTML.

   The align attribute can take one of four defined values, left, center,
   right and justify. If the attribute is not specified then the default is
   left.

   Example 7.4. Using an Element with an Attribute

 <p align="left">The inclusion of the align attribute
   on this paragraph was superfluous, since the default is left.</p>

 <p align="center">This may appear in the center.</p>

   Some attributes only take specific values, such as left or justify. Others
   allow any value.

   Example 7.5. Single Quotes Around Attributes

 <p align='right'>I am on the right!</p>

   Attribute values in XML must be enclosed in either single or double
   quotes. Double quotes are traditional. Single quotes are useful when the
   attribute value contains double quotes.

   Information about attributes, elements, and tags is stored in catalog
   files. The Documentation Project uses standard DocBook catalogs and
   includes additional catalogs for FreeBSD-specific features. Paths to the
   catalog files are defined in an environment variable so they can be found
   by the document build tools.

  7.2.1. To Do...

   Before running the examples in this document, install textproc/docproj
   from the FreeBSD Ports Collection. This is a meta-port that downloads and
   installs the standard programs and supporting files needed by the
   Documentation Project. csh(1) users must use rehash for the shell to
   recognize new programs after they have been installed, or log out and then
   log back in again.

    1. Create example.xml, and enter this text:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <body>
     <p>This is a paragraph containing some text.</p>

     <p>This paragraph contains some more text.</p>

     <p align="right">This paragraph might be right-justified.</p>
   </body>
 </html>

    2. Try to validate this file using an XML parser.

       textproc/docproj includes the xmllint validating parser.

       Use xmllint to validate the document:

 % xmllint --valid --noout example.xml

       xmllint returns without displaying any output, showing that the
       document validated successfully.

    3. See what happens when required elements are omitted. Delete the line
       with the <title> and </title> tags, and re-run the validation.

 % xmllint --valid --noout example.xml
 example.xml:5: element head: validity error : Element head content does not follow the DTD, expecting ((script | style | meta | link | object | isindex)* , ((title , (script | style | meta | link | object | isindex)* , (base , (script | style | meta | link | object | isindex)*)?) | (base , (script | style | meta | link | object | isindex)* , title , (script | style | meta | link | object | isindex)*))), got ()

       This shows that the validation error comes from the fifth line of the
       example.xml file and that the content of the <head> is the part which
       does not follow the rules of the XHTML grammar.

       Then xmllint shows the line where the error was found and marks the
       exact character position with a ^ sign.

    4. Replace the title element.

7.3. The DOCTYPE Declaration

   The beginning of each document can specify the name of the DTD to which
   the document conforms. This DOCTYPE declaration is used by XML parsers to
   identify the DTD and ensure that the document does conform to it.

   A typical declaration for a document written to conform with version 1.0
   of the XHTML DTD looks like this:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

   That line contains a number of different components.

   <!

           The indicator shows this is an XML declaration.

   DOCTYPE

           Shows that this is an XML declaration of the document type.

   html

           Names the first element that will appear in the document.

   PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

           Lists the Formal Public Identifier (FPI) for the DTD to which this
           document conforms. The XML parser uses this to find the correct
           DTD when processing this document.

           PUBLIC is not a part of the FPI, but indicates to the XML
           processor how to find the DTD referenced in the FPI. Other ways of
           telling the XML parser how to find the DTD are shown later.

   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"

           A local filename or a URL to find the DTD.

   >

           Ends the declaration and returns to the document.

  7.3.1. Formal Public Identifiers (FPIs)

  Note:

   It is not necessary to know this, but it is useful background, and might
   help debug problems when the XML processor can not locate the DTD.

   FPIs must follow a specific syntax:

 "Owner//Keyword Description//Language"

   Owner

           The owner of the FPI.

           The beginning of the string identifies the owner of the FPI. For
           example, the FPI "ISO 8879:1986//ENTITIES Greek Symbols//EN" lists
           ISO 8879:1986 as being the owner for the set of entities for Greek
           symbols. ISO 8879:1986 is the International Organization for
           Standardization (ISO) number for the SGML standard, the
           predecessor (and a superset) of XML.

           Otherwise, this string will either look like -//Owner or +//Owner
           (notice the only difference is the leading + or -).

           If the string starts with - then the owner information is
           unregistered, with a + identifying it as registered.

           ISO 9070:1991 defines how registered names are generated. It might
           be derived from the number of an ISO publication, an ISBN code, or
           an organization code assigned according to ISO 6523. Additionally,
           a registration authority could be created in order to assign
           registered names. The ISO council delegated this to the American
           National Standards Institute (ANSI).

           Because the FreeBSD Project has not been registered, the owner
           string is -//FreeBSD. As seen in the example, the W3C are not a
           registered owner either.

   Keyword

           There are several keywords that indicate the type of information
           in the file. Some of the most common keywords are DTD, ELEMENT,
           ENTITIES, and TEXT. DTD is used only for DTD files, ELEMENT is
           usually used for DTD fragments that contain only entity or element
           declarations. TEXT is used for XML content (text and tags).

   Description

           Any description can be given for the contents of this file. This
           may include version numbers or any short text that is meaningful
           and unique for the XML system.

   Language

           An ISO two-character code that identifies the native language for
           the file. EN is used for English.

    7.3.1.1. catalog Files

   With the syntax above, an XML processor needs to have some way of turning
   the FPI into the name of the file containing the DTD. A catalog file
   (typically called catalog) contains lines that map FPIs to filenames. For
   example, if the catalog file contained the line:

 PUBLIC  "-//W3C//DTD XHTML 1.0 Transitional//EN"             "1.0/transitional.dtd"

   The XML processor knows that the DTD is called transitional.dtd in the 1.0
   subdirectory of the directory that held catalog.

   Examine the contents of /usr/local/share/xml/dtd/xhtml/catalog.xml. This
   is the catalog file for the XHTML DTDs that were installed as part of the
   textproc/docproj port.

  7.3.2. Alternatives to FPIs

   Instead of using an FPI to indicate the DTD to which the document conforms
   (and therefore, which file on the system contains the DTD), the filename
   can be explicitly specified.

   The syntax is slightly different:

 <!DOCTYPE html SYSTEM "/path/to/file.dtd">

   The SYSTEM keyword indicates that the XML processor should locate the DTD
   in a system specific fashion. This typically (but not always) means the
   DTD will be provided as a filename.

   Using FPIs is preferred for reasons of portability. If the SYSTEM
   identifier is used, then the DTD must be provided and kept in the same
   location for everyone.

7.4. Escaping Back to XML

   Some of the underlying XML syntax can be useful within documents. For
   example, comments can be included in the document, and will be ignored by
   the parser. Comments are entered using XML syntax. Other uses for XML
   syntax will be shown later.

   XML sections begin with a <! tag and end with a >. These sections contain
   instructions for the parser rather than elements of the document.
   Everything between these tags is XML syntax. The DOCTYPE declaration shown
   earlier is an example of XML syntax included in the document.

7.5. Comments

   An XML document may contain comments. They may appear anywhere as long as
   they are not inside tags. They are even allowed in some locations inside
   the DTD (e.g., between entity declarations).

   XML comments start with the string "<!--" and end with the string "-->".

   Here are some examples of valid XML comments:

   Example 7.6. XML Generic Comments

 <!-- This is inside the comment -->

 <!--This is another comment-->

 <!-- This is how you
      write multiline comments -->

 <p>A simple <!-- Comment inside an element's content --> paragraph.</p>

   XML comments may contain any strings except "--":

   Example 7.7. Erroneous XML Comment

 <!-- This comment--is wrong -->

  7.5.1. To Do...

    1. Add some comments to example.xml, and check that the file still
       validates using xmllint.

    2. Add some invalid comments to example.xml, and see the error messages
       that xmllint gives when it encounters an invalid comment.

7.6. Entities

   Entities are a mechanism for assigning names to chunks of content. As an
   XML parser processes a document, any entities it finds are replaced by the
   content of the entity.

   This is a good way to have re-usable, easily changeable chunks of content
   in XML documents. It is also the only way to include one marked up file
   inside another using XML.

   There are two types of entities for two different situations: general
   entities and parameter entities.

  7.6.1. General Entities

   General entities are used to assign names to reusable chunks of text.
   These entities can only be used in the document. They cannot be used in an
   XML context.

   To include the text of a general entity in the document, include
   &entity-name; in the text. For example, consider a general entity called
   current.version which expands to the current version number of a product.
   To use it in the document, write:

 <para>The current version of our product is
   &current.version;.</para>

   When the version number changes, edit the definition of the general
   entity, replacing the value. Then reprocess the document.

   General entities can also be used to enter characters that could not
   otherwise be included in an XML document. For example, < and & cannot
   normally appear in an XML document. The XML parser sees the < symbol as
   the start of a tag. Likewise, when the & symbol is seen, the next text is
   expected to be an entity name.

   These symbols can be included by using two predefined general entities:
   &lt; and &amp;.

   General entities can only be defined within an XML context. Such
   definitions are usually done immediately after the DOCTYPE declaration.

   Example 7.8. Defining General Entities

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY current.version    "3.0-RELEASE">
 <!ENTITY last.version       "2.2.7-RELEASE">
 ]>

   The DOCTYPE declaration has been extended by adding a square bracket at
   the end of the first line. The two entities are then defined over the next
   two lines, the square bracket is closed, and then the DOCTYPE declaration
   is closed.

   The square brackets are necessary to indicate that the DTD indicated by
   the DOCTYPE declaration is being extended.

  7.6.2. Parameter Entities

   Parameter entities, like general entities, are used to assign names to
   reusable chunks of text. But parameter entities can only be used within an
   XML context.

   Parameter entity definitions are similar to those for general entities.
   However, parameter entries are included with %entity-name;. The definition
   also includes the % between the ENTITY keyword and the name of the entity.

   For a mnemonic, think "Parameter entities use the Percent symbol".

   Example 7.9. Defining Parameter Entities

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY % param.some "some">
 <!ENTITY % param.text "text">
 <!ENTITY % param.new  "%param.some more %param.text">

 <!-- %param.new now contains "some more text" -->
 ]>

  7.6.3. To Do...

    1. Add a general entity to example.xml.

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY version "1.1">
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <!-- There may be some comments in here as well -->

   <body>
     <p>This is a paragraph containing some text.</p>

     <p>This paragraph contains some more text.</p>

     <p align="right">This paragraph might be right-justified.</p>

     <p>The current version of this document is: &version;</p>
   </body>
 </html>

    2. Validate the document using xmllint.

    3. Load example.xml into a web browser. It may have to be copied to
       example.html before the browser recognizes it as an XHTML document.

       Older browsers with simple parsers may not render this file as
       expected. The entity reference &version; may not be replaced by the
       version number, or the XML context closing ]> may not be recognized
       and instead shown in the output.

    4. The solution is to normalize the document with an XML normalizer. The
       normalizer reads valid XML and writes equally valid XML which has been
       transformed in some way. One way the normalizer transforms the input
       is by expanding all the entity references in the document, replacing
       the entities with the text that they represent.

       xmllint can be used for this. It also has an option to drop the
       initial DTD section so that the closing ]> does not confuse browsers:

 % xmllint --noent --dropdtd example.xml > example.html

       A normalized copy of the document with entities expanded is produced
       in example.html, ready to load into a web browser.

7.7. Using Entities to Include Files

   Both general and parameter entities are particularly useful for including
   one file inside another.

  7.7.1. Using General Entities to Include Files

   Consider some content for an XML book organized into files, one file per
   chapter, called chapter1.xml, chapter2.xml, and so forth, with a book.xml
   that will contain these chapters.

   In order to use the contents of these files as the values for entities,
   they are declared with the SYSTEM keyword. This directs the XML parser to
   include the contents of the named file as the value of the entity.

   Example 7.10. Using General Entities to Include Files

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY chapter.1 SYSTEM "chapter1.xml">
 <!ENTITY chapter.2 SYSTEM "chapter2.xml">
 <!ENTITY chapter.3 SYSTEM "chapter3.xml">
 <!-- And so forth -->
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <!-- Use the entities to load in the chapters -->

   &chapter.1;
   &chapter.2;
   &chapter.3;
 </html>

  Warning:

   When using general entities to include other files within a document, the
   files being included (chapter1.xml, chapter2.xml, and so on) must not
   start with a DOCTYPE declaration. This is a syntax error because entities
   are low-level constructs and they are resolved before any parsing happens.

  7.7.2. Using Parameter Entities to Include Files

   Parameter entities can only be used inside an XML context. Including a
   file in an XML context can be used to ensure that general entities are
   reusable.

   Suppose that there are many chapters in the document, and these chapters
   were reused in two different books, each book organizing the chapters in a
   different fashion.

   The entities could be listed at the top of each book, but that quickly
   becomes cumbersome to manage.

   Instead, place the general entity definitions inside one file, and use a
   parameter entity to include that file within the document.

   Example 7.11. Using Parameter Entities to Include Files

   Place the entity definitions in a separate file called chapters.ent and
   containing this text:

 <!ENTITY chapter.1 SYSTEM "chapter1.xml">
 <!ENTITY chapter.2 SYSTEM "chapter2.xml">
 <!ENTITY chapter.3 SYSTEM "chapter3.xml">

   Create a parameter entity to refer to the contents of the file. Then use
   the parameter entity to load the file into the document, which will then
   make all the general entities available for use. Then use the general
   entities as before:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!-- Define a parameter entity to load in the chapter general entities -->
 <!ENTITY % chapters SYSTEM "chapters.ent">

 <!-- Now use the parameter entity to load in this file -->
 %chapters;
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   &chapter.1;
   &chapter.2;
   &chapter.3;
 </html>

  7.7.3. To Do...

    7.7.3.1. Use General Entities to Include Files

    1. Create three files, para1.xml, para2.xml, and para3.xml.

       Put content like this in each file:

 <p>This is the first paragraph.</p>

    2. Edit example.xml so that it looks like this:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY version "1.1">
 <!ENTITY para1 SYSTEM "para1.xml">
 <!ENTITY para2 SYSTEM "para2.xml">
 <!ENTITY para3 SYSTEM "para3.xml">
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <body>
     <p>The current version of this document is: &version;</p>

     &para1;
     &para2;
     &para3;
   </body>
 </html>

    3. Produce example.html by normalizing example.xml.

 % xmllint --dropdtd --noent example.xml > example.html

    4. Load example.html into the web browser and confirm that the paran.xml
       files have been included in example.html.

    7.7.3.2. Use Parameter Entities to Include Files

  Note:

   The previous steps must have completed before this step.

    1. Edit example.xml so that it looks like this:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY % entities SYSTEM "entities.ent"> %entities;
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <body>
     <p>The current version of this document is: &version;</p>

     &para1;
     &para2;
     &para3;
   </body>
 </html>

    2. Create a new file called entities.ent with this content:

 <!ENTITY version "1.1">
 <!ENTITY para1 SYSTEM "para1.xml">
 <!ENTITY para2 SYSTEM "para2.xml">
 <!ENTITY para3 SYSTEM "para3.xml">

    3. Produce example.html by normalizing example.xml.

 % xmllint --dropdtd --noent example.xml > example.html

    4. Load example.html into the web browser and confirm that the paran.xml
       files have been included in example.html.

7.8. Marked Sections

   XML provides a mechanism to indicate that particular pieces of the
   document should be processed in a special way. These are called "marked
   sections".

   Example 7.12. Structure of a Marked Section

 <![KEYWORD[
   Contents of marked section
 ]]>

   As expected of an XML construct, a marked section starts with <!.

   The first square bracket begins the marked section.

   KEYWORD describes how this marked section is to be processed by the
   parser.

   The second square bracket indicates the start of the marked section's
   content.

   The marked section is finished by closing the two square brackets, and
   then returning to the document context from the XML context with >.

  7.8.1. Marked Section Keywords

    7.8.1.1. CDATA

   These keywords denote the marked sections content model, and allow you to
   change it from the default.

   When an XML parser is processing a document, it keeps track of the
   "content model".

   The content model describes the content the parser is expecting to see and
   what it will do with that content.

   The CDATA content model is one of the most useful.

   CDATA is for "Character Data". When the parser is in this content model,
   it expects to see only characters. In this model the < and & symbols lose
   their special status, and will be treated as ordinary characters.

  Note:

   When using CDATA in examples of text marked up in XML, remember that the
   content of CDATA is not validated. The included text must be check with
   other means. For example, the content could be written in another
   document, validated, and then pasted into the CDATA section.

   Example 7.13. Using a CDATA Marked Section

 <para>Here is an example of how to include some text that contains
   many <literal>&lt;</literal> and <literal>&amp;</literal>
   symbols.  The sample text is a fragment of
   <acronym>XHTML</acronym>.  The surrounding text (<para> and
   <programlisting>) are from DocBook.</para>

 <programlisting><![CDATA[<p>This is a sample that shows some of the
   elements within <acronym>XHTML</acronym>.  Since the angle
   brackets are used so many times, it is simpler to say the whole
   example is a CDATA marked section than to use the entity names for
   the left and right angle brackets throughout.</p>

     <ul>
       <li>This is a listitem</li>
       <li>This is a second listitem</li>
       <li>This is a third listitem</li>
     </ul>

     <p>This is the end of the example.</p>]]></programlisting>

    7.8.1.2. INCLUDE and IGNORE

   When the keyword is INCLUDE, then the contents of the marked section will
   be processed. When the keyword is IGNORE, the marked section is ignored
   and will not be processed. It will not appear in the output.

   Example 7.14. Using INCLUDE and IGNORE in Marked Sections

 <![INCLUDE[
   This text will be processed and included.
 ]]>

 <![IGNORE[
   This text will not be processed or included.
 ]]>

   By itself, this is not too useful. Text to be removed from the document
   could be cut out, or wrapped in comments.

   It becomes more useful when controlled by parameter entities, yet this
   usage is limited to entity files.

   For example, suppose that documentation was produced in a hard-copy
   version and an electronic version. Some extra text is desired in the
   electronic version content that was not to appear in the hard-copy.

   Create an entity file that defines general entities to include each
   chapter and guard these definitions with a parameter entity that can be
   set to either INCLUDE or IGNORE to control whether the entity is defined.
   After these conditional general entity definitions, place one more
   definition for each general entity to set them to an empty value. This
   technique makes use of the fact that entity definitions cannot be
   overridden but the first definition always takes effect. So the inclusion
   of the chapter is controlled with the corresponding parameter entity. Set
   to INCLUDE, the first general entity definition will be read and the
   second one will be ignored. Set to IGNORE, the first definition will be
   ignored and the second one will take effect.

   Example 7.15. Using a Parameter Entity to Control a Marked Section

 <!ENTITY % electronic.copy "INCLUDE">

 <![%electronic.copy;[
 <!ENTITY chap.preface   SYSTEM "preface.xml">
 ]]>

 <!ENTITY chap.preface "">

   When producing the hard-copy version, change the parameter entity's
   definition to:

 <!ENTITY % electronic.copy "IGNORE">

  7.8.2. To Do...

    1. Modify entities.ent to contain the following:

 <!ENTITY version "1.1">
 <!ENTITY % conditional.text "IGNORE">

 <![%conditional.text;[
 <!ENTITY para1 SYSTEM "para1.xml">
 ]]>

 <!ENTITY para1 "">

 <!ENTITY para2 SYSTEM "para2.xml">
 <!ENTITY para3 SYSTEM "para3.xml">

    2. Normalize example.xml and notice that the conditional text is not
       present in the output document. Set the parameter entity guard to
       INCLUDE and regenerate the normalized document and the text will
       appear again. This method makes sense if there are more conditional
       chunks depending on the same condition. For example, to control
       generating printed or online text.

7.9. Conclusion

   That is the conclusion of this XML primer. For reasons of space and
   complexity, several things have not been covered in depth (or at all).
   However, the previous sections cover enough XML to introduce the
   organization of the FDP documentation.

                            Chapter 8. XHTML Markup

   Table of Contents

   8.1. Introduction

   8.2. Formal Public Identifier (FPI)

   8.3. Sectional Elements

   8.4. Block Elements

   8.5. In-line Elements

8.1. Introduction

   This chapter describes usage of the XHTML markup language used for the
   FreeBSD web site.

   XHTML is the XML version of the HyperText Markup Language, the markup
   language of choice on the World Wide Web. More information can be found at
   http://www.w3.org/.

   XHTML is used to mark up pages on the FreeBSD web site. It is usually not
   used to mark up other documentation, since DocBook offers a far richer set
   of elements from which to choose. Consequently, XHTML pages will normally
   only be encountered when writing for the web site.

   HTML has gone through a number of versions. The XML-compliant version
   described here is called XHTML. The latest widespread version is XHTML
   1.0, available in both strict and transitional variants.

   The XHTML DTDs are available from the Ports Collection in textproc/xhtml.
   They are automatically installed by the textproc/docproj port.

  Note:

   This is not an exhaustive list of elements, since that would just repeat
   the documentation for XHTML. The aim is to list those elements most
   commonly used. Please post questions about elements or uses not covered
   here to the FreeBSD documentation project mailing list.

  Inline Versus Block:

   In the remainder of this document, when describing elements, inline means
   that the element can occur within a block element, and does not cause a
   line break. A block element, by comparison, will cause a line break (and
   other processing) when it is encountered.

8.2. Formal Public Identifier (FPI)

   There are a number of XHTML FPIs, depending upon the version, or level of
   XHTML to which a document conforms. Most XHTML documents on the FreeBSD
   web site comply with the transitional version of XHTML 1.0.

 PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

8.3. Sectional Elements

   An XHTML document is normally split into two sections. The first section,
   called the head, contains meta-information about the document, such as its
   title, the name of the author, the parent document, and so on. The second
   section, the body, contains content that will be displayed to the user.

   These sections are indicated with head and body elements respectively.
   These elements are contained within the top-level html element.

   Example 8.1. Normal XHTML Document Structure

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
           <title>The Document's Title</title>
   </head>

   <body>

     ...

   </body>
 </html>

8.4. Block Elements

  8.4.1. Headings

   XHTML has tags to denote headings in the document at up to six different
   levels.

   The largest and most prominent heading is h1, then h2, continuing down to
   h6.

   The element's content is the text of the heading.

   Example 8.2. h1, h2, and Other Header Tags

   Usage:

 <h1>First section</h1>

 <!-- Document introduction goes here -->

 <h2>This is the heading for the first section</h2>

 <!-- Content for the first section goes here -->

 <h3>This is the heading for the first sub-section</h3>

 <!-- Content for the first sub-section goes here -->

 <h2>This is the heading for the second section</h2>

 <!-- Content for the second section goes here -->

   Generally, an XHTML page should have one first level heading (h1). This
   can contain many second level headings (h2), which can in turn contain
   many third level headings. Do not leave gaps in the numbering.

  8.4.2. Paragraphs

   XHTML supports a single paragraph element, p.

   Example 8.3. p Example

   Usage:

 <p>This is a paragraph.  It can contain just about any
   other element.</p>

  8.4.3. Block Quotations

   A block quotation is an extended quotation from another document that will
   appear in a separate paragraph.

   Example 8.4. blockquote Example

   Usage:

 <p>A small excerpt from the US Constitution:</p>

 <blockquote>We the People of the United States, in Order to form
   a more perfect Union, establish Justice, insure domestic
   Tranquility, provide for the common defence, promote the general
   Welfare, and secure the Blessings of Liberty to ourselves and our
   Posterity, do ordain and establish this Constitution for the
   United States of America.</blockquote>

  8.4.4. Lists

   XHTML can present the user with three types of lists: ordered, unordered,
   and definition.

   Entries in an ordered list will be numbered, while entries in an unordered
   list will be preceded by bullet points. Definition lists have two sections
   for each entry. The first section is the term being defined, and the
   second section is the definition.

   Ordered lists are indicated by the ol element, unordered lists by the ul
   element, and definition lists by the dl element.

   Ordered and unordered lists contain listitems, indicated by the li
   element. A listitem can contain textual content, or it may be further
   wrapped in one or more p elements.

   Definition lists contain definition terms (dt) and definition descriptions
   (dd). A definition term can only contain inline elements. A definition
   description can contain other block elements.

   Example 8.5. ul and ol Example

   Usage:

 <p>An unordered list.  Listitems will probably be
   preceded by bullets.</p>

 <ul>
   <li>First item</li>

   <li>Second item</li>

   <li>Third item</li>
 </ul>

 <p>An ordered list, with list items consisting of multiple
   paragraphs.  Each item (note: not each paragraph) will be
   numbered.</p>

 <ol>
   <li><p>This is the first item.  It only has one paragraph.</p></li>

   <li><p>This is the first paragraph of the second item.</p>

     <p>This is the second paragraph of the second item.</p></li>

   <li><p>This is the first and only paragraph of the third
     item.</p></li>
 </ol>

   Example 8.6. Definition Lists with dl

   Usage:

 <dl>
   <dt>Term 1</dt>

   <dd><p>Paragraph 1 of definition 1.</p>

     <p>Paragraph 2 of definition 1.</p></dd>

   <dt>Term 2</dt>

   <dd><p>Paragraph 1 of definition 2.</p></dd>

   <dt>Term 3</dt>

   <dd><p>Paragraph 1 of definition 3.</p></dd>
 </dl>

  8.4.5. Pre-formatted Text

   Pre-formatted text is shown to the user exactly as it is in the file. Text
   is shown in a fixed font. Multiple spaces and line breaks are shown
   exactly as they are in the file.

   Wrap pre-formatted text in the pre element.

   Example 8.7. pre Example

   For example, the pre tags could be used to mark up an email message:

 <pre>  From: nik@FreeBSD.org
   To: freebsd-doc@FreeBSD.org
   Subject: New documentation available

   There is a new copy of my primer for contributors to the FreeBSD
   Documentation Project available at

     &lt;URL:https://people.FreeBSD.org/~nik/primer/index.html&gt;

   Comments appreciated.

   N</pre>

   Keep in mind that < and & still are recognized as special characters in
   pre-formatted text. This is why the example shown had to use &lt; instead
   of <. For consistency, &gt; was used in place of >, too. Watch out for the
   special characters that may appear in text copied from a plain-text
   source, like an email message or program code.

  8.4.6. Tables

   Mark up tabular information using the table element. A table consists of
   one or more table rows (tr), each containing one or more cells of table
   data (td). Each cell can contain other block elements, such as paragraphs
   or lists. It can also contain another table (this nesting can repeat
   indefinitely). If the cell only contains one paragraph then the pelement
   is not needed.

   Example 8.8. Simple Use of table

   Usage:

 <p>This is a simple 2x2 table.</p>

 <table>
   <tr>
     <td>Top left cell</td>

     <td>Top right cell</td>
   </tr>

   <tr>
     <td>Bottom left cell</td>

     <td>Bottom right cell</td>
   </tr>
 </table>

   A cell can span multiple rows and columns by adding the rowspan or colspan
   attributes with values for the number of rows or columns to be spanned.

   Example 8.9. Using rowspan

   Usage:

 <p>One tall thin cell on the left, two short cells next to
   it on the right.</p>

 <table>
   <tr>
     <td rowspan="2">Long and thin</td>
   </tr>

   <tr>
     <td>Top cell</td>

     <td>Bottom cell</td>
   </tr>
 </table>

   Example 8.10. Using colspan

   Usage:

 <p>One long cell on top, two short cells below it.</p>

 <table>
   <tr>
     <td colspan="2">Top cell</td>
   </tr>

   <tr>
     <td>Bottom left cell</td>

     <td>Bottom right cell</td>
   </tr>
 </table>

   Example 8.11. Using rowspan and colspan Together

   Usage:

 <p>On a 3x3 grid, the top left block is a 2x2 set of
   cells merged into one.  The other cells are normal.</p>

 <table>
   <tr>
     <td colspan="2" rowspan="2">Top left large cell</td>

     <td>Top right cell</td>
   </tr>

   <tr>
     <!-- Because the large cell on the left merges into
          this row, the first <td> will occur on its
          right -->

     <td>Middle right cell</td>
   </tr>

   <tr>
     <td>Bottom left cell</td>

     <td>Bottom middle cell</td>

     <td>Bottom right cell</td>
   </tr>
 </table>

8.5. In-line Elements

  8.5.1. Emphasizing Information

   Two levels of emphasis are available in XHTML, em and strong. em is for a
   normal level of emphasis and strong indicates stronger emphasis.

   em is typically rendered in italic and strong is rendered in bold. This is
   not always the case, and should not be relied upon. According to best
   practices, web pages only hold structural and semantical information, and
   stylesheets are later applied to them. Think of semantics, not formatting,
   when using these tags.

   Example 8.12. em and strong Example

   Usage:

 <p><em>This</em> has been emphasized, while
   <strong>this</strong> has been strongly emphasized.</p>

  8.5.2. Indicating Fixed-Pitch Text

   Content that should be rendered in a fixed pitch (typewriter) typeface is
   tagged with tt (for "teletype").

   Example 8.13. tt Example

   Usage:

 <p>Many system settings are stored in
   <tt>/etc</tt>.</p>

  8.5.3. Links

  Note:

   Links are also inline elements.

    8.5.3.1. Linking to Other Documents on the Web

   A link points to the URL of a document on the web. The link is indicated
   with a, and the href attribute contains the URL of the target document.
   The content of the element becomes the link, indicated to the user by
   showing it in a different color or with an underline.

   Example 8.14. Using <a href="...">

   Usage:

 <p>More information is available at the
   <a href="http://www.&os;.org/">&os; web site</a>.</p>

   This link always takes the user to the top of the linked document.

    8.5.3.2. Linking to Specific Parts of Documents

   To link to a specific point within a document, that document must include
   an anchor at the desired point. Anchors are included by setting the id
   attribute of an element to a name. This example creates an anchor by
   setting the id attribute of a p element.

   Example 8.15. Creating an Anchor

   Usage:

 <p id="samplepara">This paragraph can be referenced
   in other links with the name <tt>samplepara</tt>.</p>

   Links to anchors are similar to plain links, but include a # symbol and
   the anchor's ID at the end of the URL.

   Example 8.16. Linking to a Named Part of a Different Document

   The samplepara example is part of a document called foo.html. A link to
   that specific paragraph in the document is constructed in this example.

 <p>More information can be found in the
   <a href="foo.html#samplepara">sample paragraph</a> of
   <tt>foo.html</tt>.</p>

   To link to a named anchor within the same document, omit the document's
   URL, and just use the # symbol followed by the name of the anchor.

   Example 8.17. Linking to a Named Part of the Same Document

   The samplepara example resides in this document. To link to it:

 <p>More information can be found in the
   <a href="#samplepara">sample paragraph</a> of this
   document.</p>

                           Chapter 9. DocBook Markup

   Table of Contents

   9.1. Introduction

   9.2. FreeBSD Extensions

   9.3. Formal Public Identifier (FPI)

   9.4. Document Structure

   9.5. Block Elements

   9.6. In-line Elements

   9.7. Images

   9.8. Links

9.1. Introduction

   This chapter is an introduction to DocBook as it is used for FreeBSD
   documentation. DocBook is a large and complex markup system, but the
   subset described here covers the parts that are most widely used for
   FreeBSD documentation. While a moderate subset is covered, it is
   impossible to anticipate every situation. Please post questions that this
   document does not answer to the FreeBSD documentation project mailing
   list.

   DocBook was originally developed by HaL Computer Systems and O'Reilly &
   Associates to be a Document Type Definition (DTD) for writing technical
   documentation [1]. Since 1998 it is maintained by the DocBook Technical
   Committee. As such, and unlike LinuxDoc and XHTML, DocBook is very heavily
   oriented towards markup that describes what something is, rather than
   describing how it should be presented.

   The DocBook DTD is available from the Ports Collection in the
   textproc/docbook-xml port. It is automatically installed as part of the
   textproc/docproj port.

  Formal Versus Informal:

   Some elements may exist in two forms, formal and informal. Typically, the
   formal version of the element will consist of a title followed by the
   informal version of the element. The informal version will not have a
   title.

  Inline Versus Block:

   In the remainder of this document, when describing elements, inline means
   that the element can occur within a block element, and does not cause a
   line break. A block element, by comparison, will cause a line break (and
   other processing) when it is encountered.

9.2. FreeBSD Extensions

   The FreeBSD Documentation Project has extended the DocBook DTD with
   additional elements and entities. These additions serve to make some of
   the markup easier or more precise.

   Throughout the rest of this document, the term "DocBook" is used to mean
   the FreeBSD-extended DocBook DTD.

  Note:

   Most of these extensions are not unique to FreeBSD, it was just felt that
   they were useful enhancements for this particular project. Should anyone
   from any of the other *nix camps (NetBSD, OpenBSD, Linux, ...) be
   interested in collaborating on a standard DocBook extension set, please
   contact Documentation Engineering Team <doceng@FreeBSD.org>.

  9.2.1. FreeBSD Elements

   The additional FreeBSD elements are not (currently) in the Ports
   Collection. They are stored in the FreeBSD Subversion tree, as
   head/share/xml/freebsd.dtd.

   FreeBSD-specific elements used in the examples below are clearly marked.

  9.2.2. FreeBSD Entities

   This table shows some of the most useful entities available in the FDP.
   For a complete list, see the *.ent files in doc/share/xml.

                                                                                                                                                              
FreeBSD Name Entities           
&os;                            FreeBSD                                                                                                                       
&os.stable;                     FreeBSD-STABLE                                                                                                                
&os.current;                    FreeBSD-CURRENT                                                                                                               
                                                                                                                                                              
Manual Page Entities            
&man.ls.1;                      ls(1)                                                     Usage: &man.ls.1; is the manual page for <command>ls</command>.     
&man.cp.1;                      cp(1)                                                     Usage: The manual page for <command>cp</command> is &man.cp.1;.     
&man.command.sectionnumber;     link to command manual page in section sectionnumber      Entities are defined for all the FreeBSD manual pages.              
                                                                                                                                                              
FreeBSD Mailing List Entities   
&a.doc;                         FreeBSD documentation project mailing list                Usage: A link to the &a.doc;.                                       
&a.questions;                   FreeBSD general questions mailing list                    Usage: A link to the &a.questions;.                                 
&a.listname;                    link to listname                                          Entities are defined for all the FreeBSD mailing lists.             
                                                                                                                                                              
FreeBSD Document Link Entities  
&url.books.handbook;            ../../../../doc/en_US.ISO8859-1/books/handbook            Usage: A link to the <link                                          
                                                                                          xlink:href="&url.books.handbook;/advanced-networking.html">Advanced 
                                                                                          Networking</link> chapter of the Handbook.                          
&url.books.bookname;            relative path to bookname                                 Entities are defined for all the FreeBSD books.                     
&url.articles.committers-guide; ../../../../doc/en_US.ISO8859-1/articles/committers-guide Usage: A link to the <link                                          
                                                                                          xlink:href="&url.articles.committers-guide;">Committer's            
                                                                                          Guide</link> article.                                               
&url.articles.articlename;      relative path to articlename                              Entities are defined for all the FreeBSD articles.                  
                                                                                                                                                              
Other Operating System Name Entities
&linux;                         Linux(R)                                                  The Linux(R) operating system.                                      
&unix;                          UNIX(R)                                                   The UNIX(R) operating system.                                       
&windows;                       Windows(R)                                                The Windows(R) operating system.                                    
                                                                                                                                                              
Miscellaneous Entities          
&prompt.root;                   #                                                         The root user prompt.                                               
&prompt.user;                   %                                                         A prompt for an unprivileged user.                                  
&postscript;                    PostScript(R)                                             The PostScript(R) programming language.                             
&tex;                           TeX                                                       The TeX typesetting language.                                       
&xorg;                          Xorg                                                      The Xorg open source X Window System.                               

9.3. Formal Public Identifier (FPI)

   In compliance with the DocBook guidelines for writing FPIs for DocBook
   customizations, the FPI for the FreeBSD extended DocBook DTD is:

 PUBLIC "-//FreeBSD//DTD DocBook V4.2-Based Extension//EN"

9.4. Document Structure

   DocBook allows structuring documentation in several ways. The FreeBSD
   Documentation Project uses two primary types of DocBook document: the book
   and the article.

   Books are organized into chapters. This is a mandatory requirement. There
   may be parts between the book and the chapter to provide another layer of
   organization. For example, the Handbook is arranged in this way.

   A chapter may (or may not) contain one or more sections. These are
   indicated with the sect1 element. If a section contains another section
   then use the sect2 element, and so on, up to sect5.

   Chapters and sections contain the remainder of the content.

   An article is simpler than a book, and does not use chapters. Instead, the
   content of an article is organized into one or more sections, using the
   same sect1 (and sect2 and so on) elements that are used in books.

   The nature of the document being written should be used to determine
   whether it is best marked up as a book or an article. Articles are well
   suited to information that does not need to be broken down into several
   chapters, and that is, relatively speaking, quite short, at up to 20-25
   pages of content. Books are best suited to information that can be broken
   up into several chapters, possibly with appendices and similar content as
   well.

   The FreeBSD tutorials are all marked up as articles, while this document,
   the FAQ, and the Handbook are all marked up as books, for example.

  9.4.1. Starting a Book

   The content of a book is contained within the book element. As well as
   containing structural markup, this element can contain elements that
   include additional information about the book. This is either
   meta-information, used for reference purposes, or additional content used
   to produce a title page.

   This additional information is contained within info.

   Example 9.1. Boilerplate book with info

 <book>
   <info>
     <title>Your Title Here</title>

     <author>
       <personname>
         <firstname>Your first name</firstname>
         <surname>Your surname</surname>
       </personname>

       <affiliation>
         <address>
           <email>Your email address</email>
         </address>
       </affiliation>
     </author>

     <copyright>
       <year>1998</year>
       <holder role="mailto:your email address">Your name</holder>
     </copyright>

     <releaseinfo>$FreeBSD$</releaseinfo>

     <abstract>
       <para>Include an abstract of the book's contents here.</para>
     </abstract>
   </info>

   ...

 </book>

  9.4.2. Starting an Article

   The content of the article is contained within the article element. As
   well as containing structural markup, this element can contain elements
   that include additional information about the article. This is either
   meta-information, used for reference purposes, or additional content used
   to produce a title page.

   This additional information is contained within info.

   Example 9.2. Boilerplate article with info

 <article>
   <info>
     <title>Your title here</title>

     <author>
       <personname>
         <firstname>Your first name</firstname>
         <surname>Your surname</surname>
       </personname>

       <affiliation>
         <address>
           <email>Your email address</email></address>
         </address>
       </affiliation>
     </author>

     <copyright>
       <year>1998</year>
       <holder role="mailto:your email address">Your name</holder>
     </copyright>

     <releaseinfo>$FreeBSD$</releaseinfo>

     <abstract>
       <para>Include an abstract of the article's contents here.</para>
     </abstract>
   </info>

   ...

 </article>

  9.4.3. Indicating Chapters

   Use chapter to mark up your chapters. Each chapter has a mandatory title.
   Articles do not contain chapters, they are reserved for books.

   Example 9.3. A Simple Chapter

 <chapter>
   <title>The Chapter's Title</title>

   ...
 </chapter>

   A chapter cannot be empty; it must contain elements in addition to title.
   If you need to include an empty chapter then just use an empty paragraph.

   Example 9.4. Empty Chapters

 <chapter>
   <title>This is An Empty Chapter</title>

   <para></para>
 </chapter>

  9.4.4. Sections Below Chapters

   In books, chapters may (but do not need to) be broken up into sections,
   subsections, and so on. In articles, sections are the main structural
   element, and each article must contain at least one section. Use the sectn
   element. The n indicates the section number, which identifies the section
   level.

   The first sectn is sect1. You can have one or more of these in a chapter.
   They can contain one or more sect2 elements, and so on, down to sect5.

   Example 9.5. Sections in Chapters

 <chapter>
   <title>A Sample Chapter</title>

   <para>Some text in the chapter.</para>

   <sect1>
     <title>First Section</title>

     ...
   </sect1>

   <sect1>
     <title>Second Section</title>

     <sect2>
       <title>First Sub-Section</title>

       <sect3>
         <title>First Sub-Sub-Section</title>

         ...
       </sect3>
     </sect2>

     <sect2>
       <title>Second Sub-Section (1.2.2)</title>

       ...
     </sect2>
   </sect1>
 </chapter>

  Note:

   Section numbers are automatically generated and prepended to titles when
   the document is rendered to an output format. The generated section
   numbers and titles from the example above will be:

     * 1.1. First Section

     * 1.2. Second Section

     * 1.2.1. First Sub-Section

     * 1.2.1.1. First Sub-Sub-Section

     * 1.2.2. Second Sub-Section

  9.4.5. Subdividing Using part Elements

   parts introduce another level of organization between book and chapter
   with one or more parts. This cannot be done in an article.

 <part>
   <title>Introduction</title>

   <chapter>
     <title>Overview</title>

     ...
   </chapter>

   <chapter>
     <title>What is FreeBSD?</title>

     ...
   </chapter>

   <chapter>
     <title>History</title>

     ...
   </chapter>
 </part>

9.5. Block Elements

  9.5.1. Paragraphs

   DocBook supports three types of paragraphs: formalpara, para, and simpara.

   Almost all paragraphs in FreeBSD documentation use para. formalpara
   includes a title element, and simpara disallows some elements from within
   para. Stick with para.

   Example 9.6. para Example

   Usage:

 <para>This is a paragraph.  It can contain just about any
   other element.</para>

   Appearance:

   This is a paragraph. It can contain just about any other element.

  9.5.2. Block Quotations

   A block quotation is an extended quotation from another document that
   should not appear within the current paragraph. These are rarely needed.

   Blockquotes can optionally contain a title and an attribution (or they can
   be left untitled and unattributed).

   Example 9.7. blockquote Example

   Usage:

 <para>A small excerpt from the US Constitution:</para>

 <blockquote>
   <title>Preamble to the Constitution of the United States</title>

   <attribution>Copied from a web site somewhere</attribution>

   <para>We the People of the United States, in Order to form a more
     perfect Union, establish Justice, insure domestic Tranquility,
     provide for the common defence, promote the general Welfare, and
     secure the Blessings of Liberty to ourselves and our Posterity, do
     ordain and establish this Constitution for the United States of
     America.</para>
 </blockquote>

   Appearance:

   A small excerpt from the US Constitution:

     Preamble to the Constitution of the United States                        
                                                                            
     We the People of the United States, in Order to form a more perfect    
     Union, establish Justice, insure domestic Tranquility, provide for the 
     common defence, promote the general Welfare, and secure the Blessings  
     of Liberty to ourselves and our Posterity, do ordain and establish     
     this Constitution for the United States of America.                    
                                           --Copied from a web site somewhere

  9.5.3. Tips, Notes, Warnings, Cautions, and Important Information

   Extra information may need to be separated from the main body of the text.
   Typically this is "meta" information of which the user should be aware.

   Several types of admonitions are available: tip, note, warning, caution,
   and important.

   Which admonition to choose depends on the situation. The DocBook
   documentation suggests:

     * Note is for information that should be heeded by all readers.

     * Important is a variation on Note.

     * Caution is for information regarding possible data loss or software
       damage.

     * Warning is for information regarding possible hardware damage or
       injury to life or limb.

   Example 9.8. tip and important Example

   Usage:

 <tip>
   <para>&os; may reduce stress.</para>
 </tip>

 <important>
   <para>Please use admonitions sparingly.  Too many admonitions
     are visually jarring and can have the opposite of the
     intended effect.</para>
 </important>

   Appearance:

  Tip:

   FreeBSD may reduce stress.

  Important:

   Please use admonitions sparingly. Too many admonitions are visually
   jarring and can have the opposite of the intended effect.

  9.5.4. Examples

   Examples can be shown with example.

   Example 9.9. example Source

   Usage:

 <example>
   <para>Empty files can be created easily:</para>

   <screen>&prompt.user; <userinput>touch file1 file2 file3</userinput></screen>
 </example>

   Appearance:

   Example 9.10. Rendered example

   Empty files can be created easily:

 % touch file1 file2 file3

  9.5.5. Lists and Procedures

   Information often needs to be presented as lists, or as a number of steps
   that must be carried out in order to accomplish a particular goal.

   To do this, use itemizedlist, orderedlist, variablelist, or procedure.
   There are other types of list elements in DocBook, but we will not cover
   them here.

   itemizedlist and orderedlist are similar to their counterparts in HTML, ul
   and ol. Each one consists of one or more listitem elements, and each
   listitem contains one or more block elements. The listitem elements are
   analogous to HTML's li tags. However, unlike HTML, they are required.

   Example 9.11. itemizedlist and orderedlist Example

   Usage:

 <itemizedlist>
   <listitem>
     <para>This is the first itemized item.</para>
   </listitem>

   <listitem>
     <para>This is the second itemized item.</para>
   </listitem>
 </itemizedlist>

 <orderedlist>
   <listitem>
     <para>This is the first ordered item.</para>
   </listitem>

   <listitem>
     <para>This is the second ordered item.</para>
   </listitem>
 </orderedlist>

   Appearance:

     * This is the first itemized item.

     * This is the second itemized item.

    1. This is the first ordered item.

    2. This is the second ordered item.

   An alternate and often useful way of presenting information is the
   variablelist. These are lists where each entry has a term and a
   description. They are well suited for many types of descriptions, and
   present information in a form that is often easier for the reader than
   sections and subsections.

   A variablelist has a title, and then pairs of term and listitem entries.

   Example 9.12. variablelist Example

   Usage:

 <variablelist>
   <varlistentry>
     <term>Parallel</term>

     <listitem>
       <para>In parallel communications, groups of bits arrive
         at the same time over multiple communications
         channels.</para>
     </listitem>
   </varlistentry>

   <varlistentry>
     <term>Serial</term>

     <listitem>
       <para>In serial communications, bits arrive one at a
         time over a single communications
         channel.</para>
     </listitem>
   </varlistentry>
 </variablelist>

   Appearance:

   Parallel

           In parallel communications, groups of bits arrive at the same time
           over multiple communications channels.

   Serial

           In serial communications, bits arrive one at a time over a single
           communications channel.

   A procedure shows a series of steps, which may in turn consist of more
   steps or substeps. Each step contains block elements and may include an
   optional title.

   Sometimes, steps are not sequential, but present a choice: do this or do
   that, but not both. For these alternative choices, use stepalternatives.

   Example 9.13. procedure Example

   Usage:

 <procedure>
   <step>
     <para>Do this.</para>
   </step>

   <step>
     <para>Then do this.</para>
   </step>

   <step>
     <substeps>
       <step>
         <para>And now do this smaller thing.</para>
       </step>

       <step>
         <para>And now do this other smaller thing.</para>
       </step>
     </substeps>
   </step>

   <step>
     <para>Finally, do one of these:</para>

     <stepalternatives>
       <step>
         <para>Go left.</para>
       </step>

       <step>
         <para>Go right.</para>
       </step>
     </stepalternatives>
   </step>
 </procedure>

   Appearance:

    1. Do this.

    2. Then do this.

    3.   a. And now do this small thing.

         b. And this other small thing.

    4. Finally, do one of these:

          * Go left.

          * Go right.

  9.5.6. Showing File Samples

   Fragments of a file (or perhaps a complete file) are shown by wrapping
   them in the programlisting element.

   White space and line breaks within programlisting are significant. In
   particular, this means that the opening tag should appear on the same line
   as the first line of the output, and the closing tag should appear on the
   same line as the last line of the output, otherwise spurious blank lines
   may be included.

   Example 9.14. programlisting Example

   Usage:

 <para>When finished, the program will look like
   this:</para>

 <programlisting>#include &lt;stdio.h&gt;

 int
 main(void)
 {
     printf("hello, world\n");
     return 0;
 }</programlisting>

   Notice how the angle brackets in the #include line need to be referenced
   by their entities instead of being included literally.

   Appearance:

   When finished, the program will look like this:

 #include <stdio.h>

 int
 main(void)
 {
     printf("hello, world\n");
     return 0;
 }

  9.5.7. Callouts

   A callout is a visual marker for referring to a piece of text or specific
   position within an example.

   Callouts are marked with the co element. Each element must have a unique
   id assigned to it. After the example, include a calloutlist that describes
   each callout.

   Example 9.15. co and calloutlist Example

 <para>When finished, the program will look like
   this:</para>

 <programlisting>#include &lt;stdio.h&gt; <co xml:id="co-ex-include"/>

 int <co xml:id="co-ex-return"/>
 main(void)
 {
     printf("hello, world\n"); <co xml:id="co-ex-printf"/>
 }</programlisting>

 <calloutlist>
   <callout arearefs="co-ex-include">
     <para>Includes the standard IO header file.</para>
   </callout>

   <callout arearefs="co-ex-return">
     <para>Specifies that <function>main()</function> returns an
       int.</para>
   </callout>

   <callout arearefs="co-ex-printf">
     <para>The <function>printf()</function> call that writes
       <literal>hello, world</literal> to standard output.</para>
   </callout>
 </calloutlist>

   Appearance:

   When finished, the program will look like this:

 #include <stdio.h> 1

 int 2
 main(void)
 {
     printf("hello, world\n"); 3
 }

   1   Includes the standard IO header file.                           
   2   Specifies that main() returns an int.                           
   3   The printf() call that writes hello, world to standard output.  

  9.5.8. Tables

   Unlike HTML, DocBook does not need tables for layout purposes, as the
   stylesheet handles those issues. Instead, just use tables for marking up
   tabular data.

   In general terms (and see the DocBook documentation for more detail) a
   table (which can be either formal or informal) consists of a table
   element. This contains at least one tgroup element, which specifies (as an
   attribute) the number of columns in this table group. Within the
   tablegroup there is one thead element, which contains elements for the
   table headings (column headings), and one tbody which contains the body of
   the table.

   Both tgroup and thead contain row elements, which in turn contain entry
   elements. Each entry element specifies one cell in the table.

   Example 9.16. informaltable Example

   Usage:

 <informaltable pgwide="1">
   <tgroup cols="2">
     <thead>
       <row>
         <entry>This is Column Head 1</entry>
         <entry>This is Column Head 2</entry>
       </row>
     </thead>

     <tbody>
       <row>
         <entry>Row 1, column 1</entry>
         <entry>Row 1, column 2</entry>
       </row>

       <row>
         <entry>Row 2, column 1</entry>
         <entry>Row 2, column 2</entry>
       </row>
     </tbody>
   </tgroup>
 </informaltable>

   Appearance:

   +------------------------------------------------------------------------+
   |       This is Column Head 1        |       This is Column Head 2       |
   |------------------------------------+-----------------------------------|
   | Row 1, column 1                    | Row 1, column 2                   |
   |------------------------------------+-----------------------------------|
   | Row 2, column 1                    | Row 2, column 2                   |
   +------------------------------------------------------------------------+

   Always use the pgwide attribute with a value of 1 with the informaltable
   element. A bug in Internet Explorer can cause the table to render
   incorrectly if this is omitted.

   Table borders can be suppressed by setting the frame attribute to none in
   the informaltable element. For example, informaltable frame="none".

   Example 9.17. Table with frame="none" Example

   Appearance:

           This is Column Head 1                This is Column Head 2         
   Row 1, column 1                       Row 1, column 2                      
   Row 2, column 1                       Row 2, column 2                      

  9.5.9. Examples for the User to Follow

   Examples for the user to follow are often necessary. Typically, these will
   consist of dialogs with the computer; the user types in a command, the
   user gets a response back, the user types another command, and so on.

   A number of distinct elements and entities come into play here.

   screen

           Everything the user sees in this example will be on the computer
           screen, so the next element is screen.

           Within screen, white space is significant.

   prompt, &prompt.root; and &prompt.user;

           Some of the things the user will be seeing on the screen are
           prompts from the computer (either from the operating system,
           command shell, or application). These should be marked up using
           prompt.

           As a special case, the two shell prompts for the normal user and
           the root user have been provided as entities. To indicate the user
           is at a shell prompt, use one of &prompt.root; and &prompt.user;
           as necessary. They do not need to be inside prompt.

  Note:

           &prompt.root; and &prompt.user; are FreeBSD extensions to DocBook,
           and are not part of the original DTD.

   userinput

           When displaying text that the user should type in, wrap it in
           userinput tags. It will be displayed differently than system
           output text.

   Example 9.18. screen, prompt, and userinput Example

   Usage:

 <screen>&prompt.user; <userinput>ls -1</userinput>
 foo1
 foo2
 foo3
 &prompt.user; <userinput>ls -1 | grep foo2</userinput>
 foo2
 &prompt.user; <userinput>su</userinput>
 <prompt>Password: </prompt>
 &prompt.root; <userinput>cat foo2</userinput>
 This is the file called 'foo2'</screen>

   Appearance:

 % ls -1
 foo1
 foo2
 foo3
 % ls -1 | grep foo2
 foo2
 % su
 Password:
 # cat foo2
 This is the file called 'foo2'

  Note:

   Even though we are displaying the contents of the file foo2, it is not
   marked up as programlisting. Reserve programlisting for showing fragments
   of files outside the context of user actions.

9.6. In-line Elements

  9.6.1. Emphasizing Information

   To emphasize a particular word or phrase, use emphasis. This may be
   presented as italic, or bold, or might be spoken differently with a
   text-to-speech system.

   There is no way to change the presentation of the emphasis within the
   document, no equivalent of HTML's b and i. If the information being
   presented is important, then consider presenting it in important rather
   than emphasis.

   Example 9.19. emphasis Example

   Usage:

 <para>&os; is without doubt <emphasis>the</emphasis>
   premiere &unix;-like operating system for the Intel
   architecture.</para>

   Appearance:

   FreeBSD is without doubt the premiere UNIX(R)-like operating system for
   the Intel architecture.

  9.6.2. Acronyms

   Many computer terms are acronyms, words formed from the first letter of
   each word in a phrase. Acronyms are marked up into acronym elements. It is
   helpful to the reader when an acronym is defined on the first use, as
   shown in the example below.

   Example 9.20. acronym Example

   Usage:

 <para>Request For Comments (<acronym>RFC</acronym>) 1149
   defined the use of avian carriers for transmission of
   Internet Protocol (<acronym>IP</acronym>) data.  The
   quantity of <acronym>IP</acronym> data currently
   transmitted in that manner is unknown.</para>

   Appearance:

   Request For Comments (RFC) 1149 defined the use of avian carriers for
   transmission of Internet Protocol (IP) data. The quantity of IP data
   currently transmitted in that manner is unknown.

  9.6.3. Quotations

   To quote text from another document or source, or to denote a phrase that
   is used figuratively, use quote. Most of the markup tags available for
   normal text are also available from within a quote.

   Example 9.21. quote Example

   Usage:

 <para>However, make sure that the search does not go beyond the
   <quote>boundary between local and public administration</quote>,
   as <acronym>RFC</acronym> 1535 calls it.</para>

   Appearance:

   However, make sure that the search does not go beyond the "boundary
   between local and public administration", as RFC 1535 calls it.

  9.6.4. Keys, Mouse Buttons, and Combinations

   To refer to a specific key on the keyboard, use keycap. To refer to a
   mouse button, use mousebutton. And to refer to combinations of key presses
   or mouse clicks, wrap them all in keycombo.

   keycombo has an attribute called action, which may be one of click,
   double-click, other, press, seq, or simul. The last two values denote
   whether the keys or buttons should be pressed in sequence, or
   simultaneously.

   The stylesheets automatically add any connecting symbols, such as +,
   between the key names, when wrapped in keycombo.

   Example 9.22. Keys, Mouse Buttons, and Combinations Example

   Usage:

 <para>To switch to the second virtual terminal, press
   <keycombo action="simul"><keycap>Alt</keycap>
     <keycap>F1</keycap></keycombo>.</para>

 <para>To exit <command>vi</command> without saving changes, type
   <keycombo action="seq"><keycap>Esc</keycap><keycap>:</keycap>
     <keycap>q</keycap><keycap>!</keycap></keycombo>.</para>

 <para>My window manager is configured so that
   <keycombo action="simul"><keycap>Alt</keycap>
     <mousebutton>right</mousebutton>
   </keycombo> mouse button is used to move windows.</para>

   Appearance:

   To switch to the second virtual terminal, press Alt+F1.

   To exit vi without saving changes, type Esc : q !.

   My window manager is configured so that Alt+right mouse button is used to
   move windows.

  9.6.5. Applications, Commands, Options, and Cites

   Both applications and commands are frequently referred to when writing
   documentation. The distinction between them is that an application is the
   name of a program or suite of programs that fulfill a particular task. A
   command is the filename of a program that the user can type and run at a
   command line.

   It is often necessary to show some of the options that a command might
   take.

   Finally, it is often useful to list a command with its manual section
   number, in the "command(number)" format so common in Unix manuals.

   Mark up application names with application.

   To list a command with its manual section number (which should be most of
   the time) the DocBook element is citerefentry. This will contain a further
   two elements, refentrytitle and manvolnum. The content of refentrytitle is
   the name of the command, and the content of manvolnum is the manual page
   section.

   This can be cumbersome to write, and so a series of general entities have
   been created to make this easier. Each entity takes the form
   &man.manual-page.manual-section;.

   The file that contains these entities is in doc/share/xml/man-refs.ent,
   and can be referred to using this FPI:

 PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN"

   Therefore, the introduction to FreeBSD documentation will usually include
   this:

 <!DOCTYPE book PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [

 <!ENTITY % man PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN">
 %man;

 ...

 ]>

   Use command to include a command name "in-line" but present it as
   something the user should type.

   Use option to mark up the options which will be passed to a command.

   When referring to the same command multiple times in close proximity, it
   is preferred to use the &man.command.section; notation to markup the first
   reference and use command to markup subsequent references. This makes the
   generated output, especially HTML, appear visually better.

   Example 9.23. Applications, Commands, and Options Example

   Usage:

 <para><application>Sendmail</application> is the most
   widely used Unix mail application.<para>

 <para><application>Sendmail</application> includes the
   <citerefentry>
     <refentrytitle>sendmail</refentrytitle>
     <manvolnum>8</manvolnum>
   </citerefentry>, &man.mailq.1;, and &man.newaliases.1;
   programs.</para>

 <para>One of the command line parameters to <citerefentry>
     <refentrytitle>sendmail</refentrytitle>
     <manvolnum>8</manvolnum>
   </citerefentry>, <option>-bp</option>, will display the current
   status of messages in the mail queue.  Check this on the command
   line by running <command>sendmail -bp</command>.</para>

   Appearance:

   Sendmail is the most widely used Unix mail application.

   Sendmail includes the sendmail(8), mailq(1), and newaliases(1) programs.

   One of the command line parameters to sendmail(8), -bp, will display the
   current status of messages in the mail queue. Check this on the command
   line by running sendmail -bp.

  Note:

   Notice how the &man.command.section; notation is easier to follow.

  9.6.6. Files, Directories, Extensions, Device Names

   To refer to the name of a file, a directory, a file extension, or a device
   name, use filename.

   Example 9.24. filename Example

   Usage:

 <para>The source for the Handbook in English is found in
   <filename>/usr/doc/en_US.ISO8859-1/books/handbook/</filename>.
   The main file is called <filename>book.xml</filename>.
   There is also a <filename>Makefile</filename> and a
   number of files with a <filename>.ent</filename> extension.</para>

 <para><filename>kbd0</filename> is the first keyboard detected
   by the system, and appears in
   <filename>/dev</filename>.</para>

   Appearance:

   The source for the Handbook in English is found in
   /usr/doc/en_US.ISO8859-1/books/handbook/. The main file is called
   book.xml. There is also a Makefile and a number of files with a .ent
   extension.

   kbd0 is the first keyboard detected by the system, and appears in /dev.

  9.6.7. The Name of Ports

  FreeBSD Extension:

   These elements are part of the FreeBSD extension to DocBook, and do not
   exist in the original DocBook DTD.

   To include the name of a program from the FreeBSD Ports Collection in the
   document, use the package tag. Since the Ports Collection can be installed
   in any number of locations, only include the category and the port name;
   do not include /usr/ports.

   By default, package refers to a binary package. To refer to a port that
   will be built from source, set the role attribute to port.

   Example 9.25. package Example

   Usage:

 <para>Install the <package>net/wireshark</package> binary
   package to view network traffic.</para>

 <para><package role="port">net/wireshark</package> can also be
   built and installed from the Ports Collection.</para>

   Appearance:

   Install the net/wireshark binary package to view network traffic.

   net/wireshark can also be built and installed from the Ports Collection.

  9.6.8. Hosts, Domains, IP Addresses, User Names, Group Names, and Other System
  Items

  FreeBSD Extension:

   These elements are part of the FreeBSD extension to DocBook, and do not
   exist in the original DocBook DTD.

   Information for "system items" is marked up with systemitem. The class
   attribute is used to identify the particular type of information shown.

   class="domainname"

           The text is a domain name, such as FreeBSD.org or ngo.org.uk.
           There is no hostname component.

   class="etheraddress"

           The text is an Ethernet MAC address, expressed as a series of 2
           digit hexadecimal numbers separated by colons.

   class="fqdomainname"

           The text is a Fully Qualified Domain Name, with both hostname and
           domain name parts.

   class="ipaddress"

           The text is an IP address, probably expressed as a dotted quad.

   class="netmask"

           The text is a network mask, which might be expressed as a dotted
           quad, a hexadecimal string, or as a / followed by a number (CIDR
           notation).

   class="systemname"

           With class="systemname" the marked up information is the simple
           hostname, such as freefall or wcarchive.

   class="username"

           The text is a username, like root.

   class="groupname"

           The text is a groupname, like wheel.

   Example 9.26. systemitem and Classes Example

   Usage:

 <para>The local machine can always be referred to by the
   name <systemitem class="systemname">localhost</systemitem>, which will have the IP
   address <systemitem class="ipaddress">127.0.0.1</systemitem>.</para>

 <para>The <systemitem class="domainname">FreeBSD.org</systemitem>
   domain contains a number of different hosts, including
   <systemitem class="fqdomainname">freefall.FreeBSD.org</systemitem> and
   <systemitem class="fqdomainname">bento.FreeBSD.org</systemitem>.</para>

 <para>When adding an <acronym>IP</acronym> alias to an
   interface (using <command>ifconfig</command>)
   <emphasis>always</emphasis> use a netmask of
   <systemitem class="netmask">255.255.255.255</systemitem> (which can
   also be expressed as
   <systemitem class="netmask">0xffffffff</systemitem>).</para>

 <para>The <acronym>MAC</acronym> address uniquely identifies
   every network card in existence.  A typical
   <acronym>MAC</acronym> address looks like
   <systemitem class="etheraddress">08:00:20:87:ef:d0</systemitem>.</para>

 <para>To carry out most system administration functions
   requires logging in as <systemitem class="username">root</systemitem>.</para>

   Appearance:

   The local machine can always be referred to by the name localhost, which
   will have the IP address 127.0.0.1.

   The FreeBSD.org domain contains a number of different hosts, including
   freefall.FreeBSD.org and bento.FreeBSD.org.

   When adding an IP alias to an interface (using ifconfig) always use a
   netmask of 255.255.255.255 (which can also be expressed as 0xffffffff).

   The MAC address uniquely identifies every network card in existence. A
   typical MAC address looks like 08:00:20:87:ef:d0.

   To carry out most system administration functions requires logging in as
   root.

  9.6.9. Uniform Resource Identifiers (URIs)

   Occasionally it is useful to show a Uniform Resource Identifier (URI)
   without making it an active hyperlink. The uri element makes this
   possible:

   Example 9.27. uri Example

   Usage:

 <para>This URL shows only as text:
   <uri>https://www.FreeBSD.org</uri>.  It does not
   create a link.</para>

   Appearance:

   This URL shows only as text: https://www.FreeBSD.org. It does not create a
   link.

   To create links, see Section 9.8, "Links".

  9.6.10. Email Addresses

   Email addresses are marked up as email elements. In the HTML output
   format, the wrapped text becomes a hyperlink to the email address. Other
   output formats that support hyperlinks may also make the email address
   into a link.

   Example 9.28. email with a Hyperlink Example

   Usage:

 <para>An email address that does not actually exist, like
   <email>notreal@example.com</email>, can be used as an
   example.</para>

   Appearance:

   An email address that does not actually exist, like <notreal@example.com>,
   can be used as an example.

   A FreeBSD-specific extension allows setting the role attribute to nolink
   to prevent the creation of the hyperlink to the email address.

   Example 9.29. email Without a Hyperlink Example

   Usage:

 <para>Sometimes a link to an email address like
   <email role="nolink">notreal@example.com</email> is not
   desired.</para>

   Appearance:

   Sometimes a link to an email address like <notreal@example.com> is not
   desired.

  9.6.11. Describing Makefiles

  FreeBSD Extension:

   These elements are part of the FreeBSD extension to DocBook, and do not
   exist in the original DocBook DTD.

   Two elements exist to describe parts of Makefiles, buildtarget and
   varname.

   buildtarget identifies a build target exported by a Makefile that can be
   given as a parameter to make. varname identifies a variable that can be
   set (in the environment, on the command line with make, or within the
   Makefile) to influence the process.

   Example 9.30. buildtarget and varname Example

   Usage:

 <para>Two common targets in a <filename>Makefile</filename>
   are <buildtarget>all</buildtarget> and
   <buildtarget>clean</buildtarget>.</para>

 <para>Typically, invoking <buildtarget>all</buildtarget> will
   rebuild the application, and invoking
   <buildtarget>clean</buildtarget> will remove the temporary
   files (<filename>.o</filename> for example) created by the
   build process.</para>

 <para><buildtarget>clean</buildtarget> may be controlled by a
   number of variables, including <varname>CLOBBER</varname>
   and <varname>RECURSE</varname>.</para>

   Appearance:

   Two common targets in a Makefile are all and clean.

   Typically, invoking all will rebuild the application, and invoking clean
   will remove the temporary files (.o for example) created by the build
   process.

   clean may be controlled by a number of variables, including CLOBBER and
   RECURSE.

  9.6.12. Literal Text

   Literal text, or text which should be entered verbatim, is often needed in
   documentation. This is text that is excerpted from another file, or which
   should be copied exactly as shown from the documentation into another
   file.

   Some of the time, programlisting will be sufficient to denote this text.
   But programlisting is not always appropriate, particularly when you want
   to include a portion of a file "in-line" with the rest of the paragraph.

   On these occasions, use literal.

   Example 9.31. literal Example

   Usage:

 <para>The <literal>maxusers 10</literal> line in the kernel
   configuration file determines the size of many system tables, and is
   a rough guide to how many simultaneous logins the system will
   support.</para>

   Appearance:

   The maxusers 10 line in the kernel configuration file determines the size
   of many system tables, and is a rough guide to how many simultaneous
   logins the system will support.

  9.6.13. Showing Items That the User Must Fill In

   There will often be times when the user is shown what to do, or referred
   to a file or command line, but cannot simply copy the example provided.
   Instead, they must supply some information themselves.

   replaceable is designed for this eventuality. Use it inside other elements
   to indicate parts of that element's content that the user must replace.

   Example 9.32. replaceable Example

   Usage:

 <screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>

   Appearance:

 % man command

   replaceable can be used in many different elements, including literal.
   This example also shows that replaceable should only be wrapped around the
   content that the user is meant to provide. The other content should be
   left alone.

   Usage:

 <para>The <literal>maxusers <replaceable>n</replaceable></literal>
   line in the kernel configuration file determines the size of many system
   tables, and is a rough guide to how many simultaneous logins the system will
   support.</para>

 <para>For a desktop workstation, <literal>32</literal> is a good value
   for <replaceable>n</replaceable>.</para>

   Appearance:

   The maxusers n line in the kernel configuration file determines the size
   of many system tables, and is a rough guide to how many simultaneous
   logins the system will support.

   For a desktop workstation, 32 is a good value for n.

  9.6.14. Showing GUI Buttons

   Buttons presented by a graphical user interface are marked with guibutton.
   To make the text look more like a graphical button, brackets and
   non-breaking spaces are added surrounding the text.

   Example 9.33. guibutton Example

   Usage:

 <para>Edit the file, then click
   <guibutton>[&nbsp;Save&nbsp;]</guibutton> to save the
   changes.</para>

   Appearance:

   Edit the file, then click [ Save ] to save the changes.

  9.6.15. Quoting System Errors

   System errors generated by FreeBSD are marked with errorname. This
   indicates the exact error that appears.

   Example 9.34. errorname Example

   Usage:

 <screen><errorname>Panic: cannot mount root</errorname></screen>

   Appearance:

 Panic: cannot mount root

9.7. Images

  Important:

   Image support in the documentation is somewhat experimental. The
   mechanisms described here are unlikely to change, but that is not
   guaranteed.

   To provide conversion between different image formats, the
   graphics/ImageMagick port must be installed. This port is not included in
   the textproc/docproj meta port, and must be installed separately.

   A good example of the use of images is the
   doc/en_US.ISO8859-1/articles/vm-design/ document. Examine the files in
   that directory to see how these elements are used together. Build
   different output formats to see how the format determines what images are
   shown in the rendered document.

  9.7.1. Image Formats

   The following image formats are currently supported. An image file will
   automatically be converted to bitmap or vector image depending on the
   output document format.

   These are the only formats in which images should be committed to the
   documentation repository.

   EPS (Encapsulated Postscript)

           Images that are primarily vector based, such as network diagrams,
           time lines, and similar, should be in this format. These images
           have a .eps extension.

   PNG (Portable Network Graphic)

           For bitmaps, such as screen captures, use this format. These
           images have the .png extension.

   PIC (PIC graphics language)

           PIC is a language for drawing simple vector-based figures used in
           the pic(1) utility. These images have the .pic extension.

   SCR (SCReen capture)

           This format is specific to screenshots of console output. The
           following command generates an SCR file shot.scr from video buffer
           of /dev/ttyv0:

 # vidcontrol -p < /dev/ttyv0 > shot.scr

           This is preferable to PNG format for screenshots because the SCR
           file contains plain text of the command lines so that it can be
           converted to a PNG image or a plain text depending on the output
           document format.

   Use the appropriate format for each image. Documentation will often have a
   mix of EPS and PNG images. The Makefiles ensure that the correct format
   image is chosen depending on the output format used. Do not commit the
   same image to the repository in two different formats.

  Important:

   The Documentation Project may eventually switch to using the SVG (Scalable
   Vector Graphic) format for vector images. However, the current state of
   SVG capable editing tools makes this impractical.

  9.7.2. Image File Locations

   Image files can be stored in one of several locations, depending on the
   document and image:

     * In the same directory as the document itself, usually done for
       articles and small books that keep all their files in a single
       directory.

     * In a subdirectory of the main document. Typically done when a large
       book uses separate subdirectories to organize individual chapters.

       When images are stored in a subdirectory of the main document
       directory, the subdirectory name must be included in their paths in
       the Makefile and the imagedata element.

     * In a subdirectory of doc/share/images named after the document. For
       example, images for the Handbook are stored in
       doc/share/images/books/handbook. Images that work for multiple
       translations are stored in this upper level of the documentation file
       tree. Generally, these are images that can be used unchanged in
       non-English translations of the document.

  9.7.3. Image Markup

   Images are included as part of a mediaobject. The mediaobject can contain
   other, more specific objects. We are concerned with two, the imageobject
   and the textobject.

   Include one imageobject, and two textobject elements. The imageobject will
   point to the name of the image file without the extension. The textobject
   elements contain information that will be presented to the user as well
   as, or instead of, the image itself.

   Text elements are shown to the reader in several situations. When the
   document is viewed in HTML, text elements are shown while the image is
   loading, or if the mouse pointer is hovered over the image, or if a
   text-only browser is being used. In formats like plain text where graphics
   are not possible, the text elements are shown instead of the graphical
   ones.

   This example shows how to include an image called fig1.png in a document.
   The image is a rectangle with an A inside it:

 <mediaobject>
   <imageobject>
     <imagedata fileref="fig1"/> 1
   </imageobject>

   <textobject>
     <literallayout class="monospaced">+---------------+ 2
 |       A       |
 +---------------+</literallayout>
   </textobject>

   <textobject>
     <phrase>A picture</phrase> 3
   </textobject>
 </mediaobject>

   1 Include an imagedata element inside the imageobject element. The fileref 
     attribute should contain the filename of the image to include, without   
     the extension. The stylesheets will work out which extension should be   
     added to the filename automatically.                                     
   2 The first textobject contains a literallayout element, where the class   
     attribute is set to monospaced. This is an opportunity to demonstrate    
     ASCII art skills. This content will be used if the document is converted 
     to plain text.                                                           
                                                                              
     Notice how the first and last lines of the content of the literallayout  
     element butt up next to the element's tags. This ensures no extraneous   
     white space is included.                                                 
   3 The second textobject contains a single phrase element. The contents of  
     this phrase will become the alt attribute for the image when this        
     document is converted to HTML.                                           

  9.7.4. Image Makefile Entries

   Images must be listed in the Makefile in the IMAGES variable. This
   variable must contain the names of all the source images. For example, if
   there are three figures, fig1.eps, fig2.png, fig3.png, then the Makefile
   should have lines like this in it.

 ...
 IMAGES= fig1.eps fig2.png fig3.png
 ...

   or

 ...
 IMAGES=  fig1.eps
 IMAGES+= fig2.png
 IMAGES+= fig3.png
 ...

   Again, the Makefile will work out the complete list of images it needs to
   build the source document, you only need to list the image files you
   provided.

  9.7.5. Images and Chapters in Subdirectories

   Be careful when separating documentation into smaller files in different
   directories (see Section 7.7.1, "Using General Entities to Include
   Files").

   Suppose there is a book with three chapters, and the chapters are stored
   in their own directories, called chapter1/chapter.xml,
   chapter2/chapter.xml, and chapter3/chapter.xml. If each chapter has images
   associated with it, place those images in each chapter's subdirectory
   (chapter1/, chapter2/, and chapter3/).

   However, doing this requires including the directory names in the IMAGES
   variable in the Makefile, and including the directory name in the
   imagedata element in the document.

   For example, if the book has chapter1/fig1.png, then chapter1/chapter.xml
   should contain:

 <mediaobject>
   <imageobject>
     <imagedata fileref="chapter1/fig1"/> 1
   </imageobject>

   ...

 </mediaobject>

   1   The directory name must be included in the fileref attribute.  

   The Makefile must contain:

 ...
 IMAGES=  chapter1/fig1.png
 ...

9.8. Links

  Note:

   Links are also in-line elements. To show a URI without creating a link,
   see Section 9.6.9, "Uniform Resource Identifiers (URIs)".

  9.8.1. xml:id Attributes

   Most DocBook elements accept an xml:id attribute to give that part of the
   document a unique name. The xml:id can be used as a target for a
   crossreference or link.

   Any portion of the document that will be a link target must have an xml:id
   attribute. Assigning an xml:id to all chapters and sections, even if there
   are no current plans to link to them, is a good idea. These xml:ids can be
   used as unique reference points by anyone referring to the HTML version of
   the document.

   Example 9.35. xml:id on Chapters and Sections Example

 <chapter xml:id="introduction">
   <title>Introduction</title>

   <para>This is the introduction.  It contains a subsection,
     which is identified as well.</para>

   <sect1 xml:id="introduction-moredetails">
     <title>More Details</title>

     <para>This is a subsection.</para>
   </sect1>
 </chapter>

   Use descriptive values for xml:id names. The values must be unique within
   the entire document, not just in a single file. In the example, the
   subsection xml:id is constructed by appending text to the chapter xml:id.
   This ensures that the xml:ids are unique. It also helps both reader and
   anyone editing the document to see where the link is located within the
   document, similar to a directory path to a file.

  9.8.2. Crossreferences with xref

   xref provides the reader with a link to jump to another section of the
   document. The target xml:id is specified in the linkend attribute, and
   xref generates the link text automatically.

   Example 9.36. xref Example

   Assume that this fragment appears somewhere in a document that includes
   the xml:id example shown above:

 <para>More information can be found
   in <xref linkend="introduction"/>.</para>

 <para>More specific information can be found
   in <xref linkend="introduction-moredetails"/>.</para>

   The link text will be generated automatically, looking like (emphasized
   text indicates the link text):

     More information can be found in Chapter 1, Introduction.

     More specific information can be found in Section 1.1, "More Details".

   The link text is generated automatically from the chapter and section
   number and title elements.

  9.8.3. Linking to Other Documents on the Web

   The link element described here allows the writer to define the link text.
   When link text is used, it is very important to be descriptive to give the
   reader an idea of where the link goes. Remember that DocBook can be
   rendered to multiple types of media. The reader might be looking at a
   printed book or other form of media where there are no links. If the link
   text is not descriptive enough, the reader might not be able to locate the
   linked section.

   The xlink:href attribute is the URL of the page, and the content of the
   element is the text that will be displayed for the user to activate.

   In many situations, it is preferable to show the actual URL rather than
   text. This can be done by leaving out the element text entirely.

   Example 9.37. link to a FreeBSD Documentation Web Page Example

   Link to the book or article URL entity. To link to a specific chapter in a
   book, add a slash and the chapter file name, followed by an optional
   anchor within the chapter. For articles, link to the article URL entity,
   followed by an optional anchor within the article. URL entities can be
   found in doc/share/xml/urls.ent.

   Usage for FreeBSD book links:

 <para>Read the <link
     xlink:href="&url.books.handbook;/svn.html#svn-intro">SVN
     introduction</link>, then pick the nearest mirror from
   the list of <link
     xlink:href="&url.books.handbook;/svn.html#svn-mirrors">Subversion
     mirror sites</link>.</para>

   Appearance:

   Read the SVN introduction, then pick the nearest mirror from the list of
   Subversion mirror sites.

   Usage for FreeBSD article links:

 <para>Read this
   <link xlink:href="&url.articles.bsdl-gpl;">article
     about the BSD license</link>, or just the
   <link xlink:href="&url.articles.bsdl-gpl;#intro">introduction</link>.</para>

   Appearance:

   Read this article about the BSD license, or just the introduction.

   Example 9.38. link to a FreeBSD Web Page Example

   Usage:

 <para>Of course, you could stop reading this document and go to the
   <link xlink:href="&url.base;/index.html">FreeBSD home page</link> instead.</para>

   Appearance:

   Of course, you could stop reading this document and go to the FreeBSD home
   page instead.

   Example 9.39. link to an External Web Page Example

   Usage:

 <para>Wikipedia has an excellent reference on
   <link
     xlink:href="http://en.wikipedia.org/wiki/GUID_Partition_Table">GUID
     Partition Tables</link>.</para>

   Appearance:

   Wikipedia has an excellent reference on GUID Partition Tables.

   The link text can be omitted to show the actual URL:

 <para>Wikipedia has an excellent reference on
   GUID Partition Tables: <link
     xlink:href="http://en.wikipedia.org/wiki/GUID_Partition_Table"></link>.</para>

   The same link can be entered using shorter notation instead of a separate
   ending tag:

 <para>Wikipedia has an excellent reference on
   GUID Partition Tables: <link
     xlink:href="http://en.wikipedia.org/wiki/GUID_Partition_Table"/>.</para>

   The two methods are equivalent. Appearance:

   Wikipedia has an excellent reference on GUID Partition Tables:
   http://en.wikipedia.org/wiki/GUID_Partition_Table.

     ----------------------------------------------------------------------

   [1] A short history can be found under
   http://www.oasis-open.org/docbook/intro.shtml#d0e41.

                            Chapter 10. Style Sheets

   Table of Contents

   10.1. CSS

   XML is concerned with content, and says nothing about how that content
   should be presented to the reader or rendered on paper. Multiple style
   sheet languages have been developed to describe visual layout, including
   Extensible Stylesheet Language Transformation (XSLT), Document Style
   Semantics and Specification Language (DSSSL), and Cascading Style Sheets
   (CSS).

   The FDP documents use XSLT stylesheets to transform DocBook into XHTML,
   and then CSS formatting is applied to the XHTML pages. Printable output is
   currently rendered with legacy DSSSL stylesheets, but this will probably
   change in the future.

10.1. CSS

   Cascading Style Sheets (CSS) are a mechanism for attaching style
   information (font, weight, size, color, and so forth) to elements in an
   XHTML document without abusing XHTML to do so.

  10.1.1. The DocBook Documents

   The FreeBSD XSLT and DSSSL stylesheets refer to docbook.css, which is
   expected to be present in the same directory as the XHTML files. The
   project-wide CSS file is copied from doc/share/misc/docbook.css when
   documents are converted to XHTML, and is installed automatically.

                            Chapter 11. Translations

   This is the FAQ for people translating the FreeBSD documentation (FAQ,
   Handbook, tutorials, manual pages, and others) to different languages.

   It is very heavily based on the translation FAQ from the FreeBSD German
   Documentation Project, originally written by Frank Gru:nder
   <elwood@mc5sys.in-berlin.de> and translated back to English by Bernd
   Warken <bwarken@mayn.de>.

   The FAQ is maintained by the Documentation Engineering Team
   <doceng@FreeBSD.org>.

   11.1. What do i18n and l10n mean?

   11.2. Is there a mailing list for translators?

   11.3. Are more translators needed?

   11.4. What languages do I need to know?

   11.5. What software do I need to know?

   11.6. How do I find out who else might be translating to the same
   language?

   11.7. No one else is translating to my language. What do I do?

   11.8. I have translated some documentation, where do I send it?

   11.9. I am the only person working on translating to this language, how do
   I submit my translation?

   11.10. Can I include language or country specific text in my translation?

   11.11. How should language specific characters be included?

   11.12. Addressing the reader

   11.13. Do I need to include any additional information in my translations?

11.1.  What do i18n and l10n mean?                                                             
       i18n means internationalization and l10n means localization. They are just a convenient 
       shorthand.                                                                              
                                                                                               
       i18n can be read as "i" followed by 18 letters, followed by "n". Similarly, l10n is "l" 
       followed by 10 letters, followed by "n".                                                
11.2.  Is there a mailing list for translators?                                                
       Yes. Different translation groups have their own mailing lists. The list of translation 
       projects has more information about the mailing lists and web sites run by each         
       translation project. In addition there is <freebsd-translators@freebsd.org> for general 
       translation discussion.                                                                 
11.3.  Are more translators needed?                                                            
       Yes. The more people work on translation the faster it gets done, and the faster        
       changes to the English documentation are mirrored in the translated documents.          
                                                                                               
       You do not have to be a professional translator to be able to help.                     
11.4.  What languages do I need to know?                                                       
       Ideally, you will have a good knowledge of written English, and obviously you will need 
       to be fluent in the language you are translating to.                                    
                                                                                               
       English is not strictly necessary. For example, you could do a Hungarian translation of 
       the FAQ from the Spanish translation.                                                   
11.5.  What software do I need to know?                                                        
       It is strongly recommended that you maintain a local copy of the FreeBSD Subversion     
       repository (at least the documentation part). This can be done by running:              
                                                                                               
       % svn checkout https://svn.FreeBSD.org/doc/head/ head                                   
                                                                                               
       svn.FreeBSD.org is a public SVN server. Verify the server certificate from the list of  
       Subversion mirror sites.                                                                
                                                                                               
         Note:                                                                                 
                                                                                               
       This will require the devel/subversion package to be installed.                         
                                                                                               
       You should be comfortable using svn. This will allow you to see what has changed        
       between different versions of the files that make up the documentation.                 
                                                                                               
       For example, to view the differences between revisions r33733 and r33734 of             
       en_US.ISO8859-1/books/fdp-primer/book.xml, run:                                         
                                                                                               
       % svn diff -r33733:33734 en_US.ISO8859-1/books/fdp-primer/book.xml                      
11.6.  How do I find out who else might be translating to the same language?                   
       The Documentation Project translations page lists the translation efforts that are      
       currently known about. If others are already working on translating documentation to    
       your language, please do not duplicate their efforts. Instead, contact them to see how  
       you can help.                                                                           
                                                                                               
       If no one is listed on that page as translating for your language, then send a message  
       to the FreeBSD documentation project mailing list in case someone else is thinking of   
       doing a translation, but has not announced it yet.                                      
11.7.  No one else is translating to my language. What do I do?                                
       Congratulations, you have just started the "FreeBSD your-language-here Documentation    
       Translation Project". Welcome aboard.                                                   
                                                                                               
       First, decide whether or not you have got the time to spare. Since you are the only     
       person working on your language at the moment it is going to be your responsibility to  
       publicize your work and coordinate any volunteers that might want to help you.          
                                                                                               
       Write an email to the Documentation Project mailing list, announcing that you are going 
       to translate the documentation, so the Documentation Project translations page can be   
       maintained.                                                                             
                                                                                               
       If there is already someone in your country providing FreeBSD mirroring services you    
       should contact them and ask if you can have some webspace for your project, and         
       possibly an email address or mailing list services.                                     
                                                                                               
       Then pick a document and start translating. It is best to start with something fairly   
       small-either the FAQ, or one of the tutorials.                                          
11.8.  I have translated some documentation, where do I send it?                               
       That depends. If you are already working with a translation team (such as the Japanese  
       team, or the German team) then they will have their own procedures for handling         
       submitted documentation, and these will be outlined on their web pages.                 
                                                                                               
       If you are the only person working on a particular language (or you are responsible for 
       a translation project and want to submit your changes back to the FreeBSD project) then 
       you should send your translation to the FreeBSD project (see the next question).        
11.9.  I am the only person working on translating to this language, how do I submit my        
       translation?                                                                            
                                                                                               
       or                                                                                      
                                                                                               
       We are a translation team, and want to submit documentation that our members have       
       translated for us.                                                                      
       First, make sure your translation is organized properly. This means that it should drop 
       into the existing documentation tree and build straight away.                           
                                                                                               
       Currently, the FreeBSD documentation is stored in a top level directory called head/.   
       Directories below this are named according to the language code they are written in, as 
       defined in ISO639 (/usr/share/misc/iso639 on a version of FreeBSD newer than 20th       
       January 1999).                                                                          
                                                                                               
       If your language can be encoded in different ways (for example, Chinese) then there     
       should be directories below this, one for each encoding format you have provided.       
                                                                                               
       Finally, you should have directories for each document.                                 
                                                                                               
       For example, a hypothetical Swedish translation might look like:                        
                                                                                               
       head/                                                                                   
           sv_SE.ISO8859-1/                                                                    
                            Makefile                                                           
                            htdocs/                                                            
                                  docproj/                                                     
                            books/                                                             
                                  faq/                                                         
                                      Makefile                                                 
                                      book.xml                                                 
                                                                                               
       sv_SE.ISO8859-1 is the name of the translation, in lang.encoding form. Note the two     
       Makefiles, which will be used to build the documentation.                               
                                                                                               
       Use tar(1) and gzip(1) to compress up your documentation, and send it to the project.   
                                                                                               
       % cd doc                                                                                
       % tar cf swedish-docs.tar sv_SE.ISO8859-1                                               
       % gzip -9 swedish-docs.tar                                                              
                                                                                               
       Put swedish-docs.tar.gz somewhere. If you do not have access to your own webspace       
       (perhaps your ISP does not let you have any) then you can email Documentation           
       Engineering Team <doceng@FreeBSD.org>, and arrange to email the files when it is        
       convenient.                                                                             
                                                                                               
       Either way, you should use Bugzilla to submit a report indicating that you have         
       submitted the documentation. It would be very helpful if you could get other people to  
       look over your translation and double check it first, since it is unlikely that the     
       person committing it will be fluent in the language.                                    
                                                                                               
       Someone (probably the Documentation Project Manager, currently Documentation            
       Engineering Team <doceng@FreeBSD.org>) will then take your translation and confirm that 
       it builds. In particular, the following things will be looked at:                       
                                                                                               
        1. Do all your files use RCS strings (such as "ID")?                                   
                                                                                               
        2. Does make all in the sv_SE.ISO8859-1 directory work correctly?                      
                                                                                               
        3. Does make install work correctly?                                                   
                                                                                               
       If there are any problems then whoever is looking at the submission will get back to    
       you to work them out.                                                                   
                                                                                               
       If there are no problems your translation will be committed as soon as possible.        
11.10. Can I include language or country specific text in my translation?                      
       We would prefer that you did not.                                                       
                                                                                               
       For example, suppose that you are translating the Handbook to Korean, and want to       
       include a section about retailers in Korea in your Handbook.                            
                                                                                               
       There is no real reason why that information should not be in the English (or German,   
       or Spanish, or Japanese, or ...) versions as well. It is feasible that an English       
       speaker in Korea might try to pick up a copy of FreeBSD whilst over there. It also      
       helps increase FreeBSD's perceived presence around the globe, which is not a bad thing. 
                                                                                               
       If you have country specific information, please submit it as a change to the English   
       Handbook (using Bugzilla) and then translate the change back to your language in the    
       translated Handbook.                                                                    
                                                                                               
       Thanks.                                                                                 
11.11. How should language specific characters be included?                                    
       Non-ASCII characters in the documentation should be included using SGML entities.       
                                                                                               
       Briefly, these look like an ampersand (&), the name of the entity, and a semi-colon     
       (;).                                                                                    
                                                                                               
       The entity names are defined in ISO8879, which is in the ports tree as                  
       textproc/iso8879.                                                                       
                                                                                               
       A few examples include:                                                                 
                                                                                               
       Entity: &eacute;                                                                        
       Appearance: e                                                                           
       Description: Small "e" with an acute accent                                             
       Entity: &Eacute;                                                                        
       Appearance: E                                                                           
       Description: Large "E" with an acute accent                                             
       Entity: &uuml;                                                                          
       Appearance: u:                                                                          
       Description: Small "u" with an umlaut                                                   
                                                                                               
       After you have installed the iso8879 port, the files in /usr/local/share/xml/iso8879    
       contain the complete list.                                                              
11.12. Addressing the reader                                                                   
       In the English documents, the reader is addressed as "you", there is no formal/informal 
       distinction as there is in some languages.                                              
                                                                                               
       If you are translating to a language which does distinguish, use whichever form is      
       typically used in other technical documentation in your language. If in doubt, use a    
       mildly polite form.                                                                     
11.13. Do I need to include any additional information in my translations?                     
       Yes.                                                                                    
                                                                                               
       The header of the English version of each document will look something like this:       
                                                                                               
       <!--                                                                                    
            The FreeBSD Documentation Project                                                  
                                                                                               
            $FreeBSD: head/en_US.ISO8859-1/books/faq/book.xml 38674 2012-04-14 13:52:52Z $     
       -->                                                                                     
                                                                                               
       The exact boilerplate may change, but it will always include a $FreeBSD$ line and the   
       phrase The FreeBSD Documentation Project. Note that the $FreeBSD part is expanded       
       automatically by Subversion, so it should be empty (just $FreeBSD$) for new files.      
                                                                                               
       Your translated documents should include their own $FreeBSD$ line, and change the       
       FreeBSD Documentation Project line to The FreeBSD language Documentation Project.       
                                                                                               
       In addition, you should add a third line which indicates which revision of the English  
       text this is based on.                                                                  
                                                                                               
       So, the Spanish version of this file might start:                                       
                                                                                               
       <!--                                                                                    
            The FreeBSD Spanish Documentation Project                                          
                                                                                               
            $FreeBSD: head/es_ES.ISO8859-1/books/faq/book.xml 38826 2012-05-17 19:12:14Z hrs $ 
            Original revision: r38674                                                          
       -->                                                                                     

                          Chapter 12. PO Translations

   Table of Contents

   12.1. Introduction

   12.2. Quick Start

   12.3. Creating New Translations

   12.4. Translating

   12.5. Tips for Translators

   12.6. Building a Translated Document

   12.7. Submitting the New Translation

12.1. Introduction

   The GNU gettext system offers translators an easy way to create and
   maintain translations of documents. Translatable strings are extracted
   from the original document into a PO (Portable Object) file. Translated
   versions of the strings are entered with a separate editor. The strings
   can be used directly or built into a complete translated version of the
   original document.

12.2. Quick Start

   The procedure shown in Section 1.1, "Quick Start" is assumed to have
   already been performed, but the TRANSLATOR option must be enabled in the
   textproc/docproj port. If that option was not enabled, display the options
   menu and enable it, then reinstall the port:

 # cd /usr/ports/textproc/docproj
 # make config
 # make clean deinstall install clean

   This example shows the creation of a Spanish translation of the short Leap
   Seconds article.

   Procedure 12.1. Install a PO Editor
     * A PO editor is needed to edit translation files. This example uses
       editors/poedit.

 # cd /usr/ports/editors/poedit
 # make install clean

   Procedure 12.2. Initial Setup

   When a new translation is first created, the directory structure and
   Makefile must be created or copied from the English original:

    1. Create a directory for the new translation. The English article source
       is in ~/doc/en_US.ISO8859-1/articles/leap-seconds/. The Spanish
       translation will go in ~/doc/es_ES.ISO8859-1/articles/leap-seconds/.
       The path is the same except for the name of the language directory.

 % svn mkdir --parents ~/doc/es_ES.ISO8859-1/articles/leap-seconds/

    2. Copy the Makefile from the original document into the translation
       directory:

 % svn cp ~/doc/en_US.ISO8859-1/articles/leap-seconds/Makefile \
     ~/doc/es_ES.ISO8859-1/articles/leap-seconds/

   Procedure 12.3. Translation

   Translating a document consists of two steps: extracting translatable
   strings from the original document, and entering translations for those
   strings. These steps are repeated until the translator feels that enough
   of the document has been translated to produce a usable translated
   document.

    1. Extract the translatable strings from the original English version
       into a PO file:

 % cd ~/doc/es_ES.ISO8859-1/articles/leap-seconds/
 % make po

    2. Use a PO editor to enter translations in the PO file. There are
       several different editors available. poedit from editors/poedit is
       shown here.

       The PO file name is the two-character language code followed by an
       underline and a two-character region code. For Spanish, the file name
       is es_ES.po.

 % poedit es_ES.po

   Procedure 12.4. Generating a Translated Document
    1. Generate the translated document:

 % cd ~/doc/es_ES.ISO8859-1/articles/leap-seconds/
 % make tran

       The name of the generated document matches the name of the English
       original, usually article.xml for articles or book.xml for books.

    2. Check the generated file by rendering it to HTML and viewing it with a
       web browser:

 % make FORMATS=html
 % firefox article.html

12.3. Creating New Translations

   The first step to creating a new translated document is locating or
   creating a directory to hold it. FreeBSD puts translated documents in a
   subdirectory named for their language and region in the format
   lang_REGION. lang is a two-character lowercase code. It is followed by an
   underscore character and then the two-character uppercase REGION code.

   Table 12.1. Language Names

    Language     Region      Translated Directory  PO File Name Character Set 
                                     Name          
   English    United States en_US.ISO8859-1        en_US.po     ISO 8859-1    
   Bengali    Bangladesh    bn_BD.UTF-8            bn_BD.po     UTF-8         
   Danish     Denmark       da_DK.ISO8859-1        da_DK.po     ISO 8859-1    
   German     Germany       de_DE.ISO8859-1        de_DE.po     ISO 8859-1    
   Greek      Greece        el_GR.ISO8859-7        el_GR.po     ISO 8859-7    
   Spanish    Spain         es_ES.ISO8859-1        es_ES.po     ISO 8859-1    
   French     France        fr_FR.ISO8859-1        fr_FR.po     ISO 8859-1    
   Hungarian  Hungary       hu_HU.ISO8859-2        hu_HU.po     ISO 8859-2    
   Italian    Italy         it_IT.ISO8859-15       it_IT.po     ISO 8859-15   
   Japanese   Japan         ja_JP.eucJP            ja_JP.po     EUC JP        
   Korean     Korea         ko_KR.UTF-8            ko_KR.po     UTF-8         
   Mongolian  Mongolia      mn_MN.UTF-8            mn_MN.po     UTF-8         
   Dutch      Netherlands   nl_NL.ISO8859-1        nl_NL.po     ISO 8859-1    
   Norwegian  Norway        no_NO.ISO8859-1        no_NO.po     ISO 8859-1    
   Polish     Poland        pl_PL.ISO8859-2        pl_PL.po     ISO 8859-2    
   Portuguese Brazil        pt_BR.ISO8859-1        pt_BR.po     ISO 8859-1    
   Russian    Russia        ru_RU.KOI8-R           ru_RU.po     KOI8-R        
   Serbian    Serbia        sr_YU.ISO8859-2        sr_YU.po     ISO 8859-2    
   Turkish    Turkey        tr_TR.ISO8859-9        tr_TR.po     ISO 8859-9    
   Chinese    China         zh_CN.UTF-8            zh_CN.po     UTF-8         
   Chinese    Taiwan        zh_TW.UTF-8            zh_TW.po     UTF-8         

   The translations are in subdirectories of the main documentation
   directory, here assumed to be ~/doc/ as shown in Section 1.1, "Quick
   Start". For example, German translations are located in
   ~/doc/de_DE.ISO8859-1/, and French translations are in
   ~/doc/fr_FR.ISO8859-1/.

   Each language directory contains separate subdirectories named for the
   type of documents, usually articles/ and books/.

   Combining these directory names gives the complete path to an article or
   book. For example, the French translation of the NanoBSD article is in
   ~/doc/fr_FR.ISO8859-1/articles/nanobsd/, and the Mongolian translation of
   the Handbook is in ~/doc/mn_MN.UTF-8/books/handbook/.

   A new language directory must be created when translating a document to a
   new language. If the language directory already exists, only a
   subdirectory in the articles/ or books/ directory is needed.

   FreeBSD documentation builds are controlled by a Makefile in the same
   directory. With simple articles, the Makefile can often just be copied
   verbatim from the original English directory. The translation process
   combines multiple separate book.xml and chapter.xml files in books into a
   single file, so the Makefile for book translations must be copied and
   modified.

   Example 12.1. Creating a Spanish Translation of the Porter's Handbook

   Create a new Spanish translation of the Porter's Handbook. The original is
   a book in ~/doc/en_US.ISO8859-1/books/porters-handbook/.

    1. The Spanish language books directory ~/doc/es_ES.ISO8859-1/books/
       already exists, so only a new subdirectory for the Porter's Handbook
       is needed:

 % cd ~/doc/es_ES.ISO8859-1/books/
 % svn mkdir porters-handbook
 A         porters-handbook

    2. Copy the Makefile from the original book:

 % cd ~/doc/es_ES.ISO8859-1/books/porters-handbook
 % svn cp ~/doc/en_US.ISO8859-1/books/porters-handbook/Makefile .
 A         Makefile

       Modify the contents of the Makefile to only expect a single book.xml:

 #
 # $FreeBSD$
 #
 # Build the FreeBSD Porter's Handbook.
 #

 MAINTAINER=doc@FreeBSD.org

 DOC?= book

 FORMATS?= html-split

 INSTALL_COMPRESSED?= gz
 INSTALL_ONLY_COMPRESSED?=

 # XML content
 SRCS=  book.xml

 # Images from the cross-document image library
 IMAGES_LIB+=    callouts/1.png
 IMAGES_LIB+=    callouts/2.png
 IMAGES_LIB+=    callouts/3.png
 IMAGES_LIB+=    callouts/4.png
 IMAGES_LIB+=    callouts/5.png
 IMAGES_LIB+=    callouts/6.png
 IMAGES_LIB+=    callouts/7.png
 IMAGES_LIB+=    callouts/8.png
 IMAGES_LIB+=    callouts/9.png
 IMAGES_LIB+=    callouts/10.png
 IMAGES_LIB+=    callouts/11.png
 IMAGES_LIB+=    callouts/12.png
 IMAGES_LIB+=    callouts/13.png
 IMAGES_LIB+=    callouts/14.png
 IMAGES_LIB+=    callouts/15.png
 IMAGES_LIB+=    callouts/16.png
 IMAGES_LIB+=    callouts/17.png
 IMAGES_LIB+=    callouts/18.png
 IMAGES_LIB+=    callouts/19.png
 IMAGES_LIB+=    callouts/20.png
 IMAGES_LIB+=    callouts/21.png

 URL_RELPREFIX?= ../../../..
 DOC_PREFIX?= ${.CURDIR}/../../..

 .include "${DOC_PREFIX}/share/mk/doc.project.mk"

       Now the document structure is ready for the translator to begin
       translating with make po.

   Example 12.2. Creating a French Translation of the PGP Keys Article

   Create a new French translation of the PGP Keys article. The original is
   an article in ~/doc/en_US.ISO8859-1/articles/pgpkeys/.

    1. The French language article directory ~/doc/fr_FR.ISO8859-1/articles/
       already exists, so only a new subdirectory for the PGP Keys article is
       needed:

 % cd ~/doc/fr_FR.ISO8859-1/articles/
 % svn mkdir pgpkeys
 A         pgpkeys

    2. Copy the Makefile from the original article:

 % cd ~/doc/fr_FR.ISO8859-1/articles/pgpkeys
 % svn cp ~/doc/en_US.ISO8859-1/articles/pgpkeys/Makefile .
 A         Makefile

       Check the contents of the Makefile. Because this is a simple article,
       in this case the Makefile can be used unchanged. The $FreeBSD...$
       version string on the second line will be replaced by the version
       control system when this file is committed.

 #
 # $FreeBSD$
 #
 # Article: PGP Keys

 DOC?= article

 FORMATS?= html
 WITH_ARTICLE_TOC?= YES

 INSTALL_COMPRESSED?= gz
 INSTALL_ONLY_COMPRESSED?=

 SRCS=   article.xml

 # To build with just key fingerprints, set FINGERPRINTS_ONLY.

 URL_RELPREFIX?= ../../../..
 DOC_PREFIX?=    ${.CURDIR}/../../..

 .include "${DOC_PREFIX}/share/mk/doc.project.mk"

       With the document structure complete, the PO file can be created with
       make po.

12.4. Translating

   The gettext system greatly reduces the number of things that must be
   tracked by a translator. Strings to be translated are extracted from the
   original document into a PO file. Then a PO editor is used to enter the
   translated versions of each string.

   The FreeBSD PO translation system does not overwrite PO files, so the
   extraction step can be run at any time to update the PO file.

   A PO editor is used to edit the file. editors/poedit is shown in these
   examples because it is simple and has minimal requirements. Other PO
   editors offer features to make the job of translating easier. The Ports
   Collection offers several of these editors, including devel/gtranslator.

   It is important to preserve the PO file. It contains all of the work that
   translators have done.

   Example 12.3. Translating the Porter's Handbook to Spanish

   Enter Spanish translations of the contents of the Porter's Handbook.

    1. Change to the Spanish Porter's Handbook directory and update the PO
       file. The generated PO file is called es_ES.po as shown in Table 12.1,
       "Language Names".

 % cd ~/doc/es_ES.ISO8859-1/books/porters-handbook
 % make po

    2. Enter translations using a PO editor:

 % poedit es_ES.po

12.5. Tips for Translators

  12.5.1. Preserving XML Tags

   Preserve XML tags that are shown in the English original.

   Example 12.4. Preserving XML Tags

   English original:

 If <acronym>NTP</acronym> is not being used

   Spanish translation:

 Si <acronym>NTP</acronym> no se utiliza

  12.5.2. Preserving Spaces

   Preserve existing spaces at the beginning and end of strings to be
   translated. The translated version must have these spaces also.

  12.5.3. Verbatim Tags

   The contents of some tags should be copied verbatim, not translated:

     * <citerefentry>

     * <command>

     * <filename>

     * <literal>

     * <manvolnum>

     * <orgname>

     * <package>

     * <programlisting>

     * <prompt>

     * <refentrytitle>

     * <screen>

     * <userinput>

     * <varname>

  12.5.4. $FreeBSD$ Strings

   The $FreeBSD$ version strings used in files require special handling. In
   examples like Example 12.1, "Creating a Spanish Translation of the
   Porter's Handbook", these strings are not meant to be expanded. The
   English documents use &dollar; entities to avoid including actual literal
   dollar signs in the file:

 &dollar;FreeBSD&dollar;

   The &dollar; entities are not seen as dollar signs by the version control
   system and so the string is not expanded into a version string.

   When a PO file is created, the &dollar; entities used in examples are
   replaced with actual dollar signs. The resulting literal $FreeBSD$ string
   will be wrongly expanded by the version control system when the file is
   committed.

   The same technique as used in the English documents can be used in the
   translation. The &dollar; is used to replace the dollar sign in the
   translation entered into the PO editor:

 &dollar;FreeBSD&dollar;

12.6. Building a Translated Document

   A translated version of the original document can be created at any time.
   Any untranslated portions of the original will be included in English in
   the resulting document. Most PO editors have an indicator that shows how
   much of the translation has been completed. This makes it easy for the
   translator to see when enough strings have been translated to make
   building the final document worthwhile.

   Example 12.5. Building the Spanish Porter's Handbook

   Build and preview the Spanish version of the Porter's Handbook that was
   created in an earlier example.

    1. Build the translated document. Because the original is a book, the
       generated document is book.xml.

 % cd ~/doc/es_ES.ISO8859-1/books/porters-handbook
 % make tran

    2. Render the translated book.xml to HTML and view it with Firefox. This
       is the same procedure used with the English version of the documents,
       and other FORMATS can be used here in the same way. See Table 5.1,
       "Common Output Formats".

 % make FORMATS=html
 % firefox book.html

12.7. Submitting the New Translation

   Prepare the new translation files for submission. This includes adding the
   files to the version control system, setting additional properties on
   them, then creating a diff for submission.

   The diff files created by these examples can be attached to a
   documentation bug report or code review.

   Example 12.6. Spanish Translation of the NanoBSD Article
    1. Add a FreeBSD version string comment as the first line of the PO file:

 #$FreeBSD$

    2. Add the Makefile, the PO file, and the generated XML translation to
       version control:

 % cd ~/doc/es_ES.ISO8859-1/articles/nanobsd/
 % ls
 Makefile        article.xml     es_ES.po
 % svn add Makefile article.xml es_ES.po
 A         Makefile
 A         article.xml
 A         es_ES.po

    3. Set the Subversion svn:keywords properties on these files to
       FreeBSD=%H so $FreeBSD$ strings are expanded into the path, revision,
       date, and author when committed:

 % svn propset svn:keywords FreeBSD=%H Makefile article.xml es_ES.po
 property 'svn:keywords' set on 'Makefile'
 property 'svn:keywords' set on 'article.xml'
 property 'svn:keywords' set on 'es_ES.po'

    4. Set the MIME types of the files. These are text/xml for books and
       articles, and text/x-gettext-translation for the PO file.

 % svn propset svn:mime-type text/x-gettext-translation es_ES.po
 property 'svn:mime-type' set on 'es_ES.po'
 % svn propset svn:mime-type text/xml article.xml
 property 'svn:mime-type' set on 'article.xml'

    5. Create a diff of the new files from the ~/doc/ base directory so the
       full path is shown with the filenames. This helps committers identify
       the target language directory.

 % cd ~/doc
 svn diff es_ES.ISO8859-1/articles/nanobsd/ > /tmp/es_nanobsd.diff

   Example 12.7. Korean UTF-8 Translation of the Explaining-BSD Article
    1. Add a FreeBSD version string comment as the first line of the PO file:

 #$FreeBSD$

    2. Add the Makefile, the PO file, and the generated XML translation to
       version control:

 % cd ~/doc/ko_KR.UTF-8/articles/explaining-bsd/
 % ls
 Makefile        article.xml     ko_KR.po
 % svn add Makefile article.xml ko_KR.po
 A         Makefile
 A         article.xml
 A         ko_KR.po

    3. Set the Subversion svn:keywords properties on these files to
       FreeBSD=%H so $FreeBSD$ strings are expanded into the path, revision,
       date, and author when committed:

 % svn propset svn:keywords FreeBSD=%H Makefile article.xml ko_KR.po
 property 'svn:keywords' set on 'Makefile'
 property 'svn:keywords' set on 'article.xml'
 property 'svn:keywords' set on 'ko_KR.po'

    4. Set the MIME types of the files. Because these files use the UTF-8
       character set, that is also specified. To prevent the version control
       system from mistaking these files for binary data, the fbsd:notbinary
       property is also set:

 % svn propset svn:mime-type 'text/x-gettext-translation; charset=UTF-8' ko_KR.po
 property 'svn:mime-type' set on 'ko_KR.po'
 % svn propset fbsd:notbinary yes ko_KR.po
 property 'fbsd:notbinary' set on 'ko_KR.po'
 % svn propset svn:mime-type 'text/xml; charset=UTF-8' article.xml
 property 'svn:mime-type' set on 'article.xml'
 % svn propset fbsd:notbinary yes article.xml
 property 'fbsd:notbinary' set on 'article.xml'

    5. Create a diff of these new files from the ~/doc/ base directory:

 % cd ~/doc
 svn diff ko_KR.UTF-8/articles/explaining-bsd > /tmp/ko-explaining.diff

                            Chapter 13. Manual Pages

   Table of Contents

   13.1. Introduction

   13.2. Sections

   13.3. Markup

   13.4. Sample Manual Page Structures

   13.5. Example Manual Pages to Use as Templates

   13.6. Resources

13.1. Introduction

   Manual pages, commonly shortened to man pages, were conceived as
   readily-available reminders for command syntax, device driver details, or
   configuration file formats. They have become an extremely valuable
   quick-reference from the command line for users, system administrators,
   and programmers.

   Although intended as reference material rather than tutorials, the
   EXAMPLES sections of manual pages often provide detailed use case.

   Manual pages are generally shown interactively by the man(1) command. When
   the user types man ls, a search is performed for a manual page matching
   ls. The first matching result is displayed.

13.2. Sections

   Manual pages are grouped into sections. Each section contains manual pages
   for a specific category of documentation:

   +------------------------------------+
   | Section Number |     Category      |
   |----------------+-------------------|
   | 1              | General Commands  |
   |----------------+-------------------|
   | 2              | System Calls      |
   |----------------+-------------------|
   | 3              | Library Functions |
   |----------------+-------------------|
   | 4              | Kernel Interfaces |
   |----------------+-------------------|
   | 5              | File Formats      |
   |----------------+-------------------|
   | 6              | Games             |
   |----------------+-------------------|
   | 7              | Miscellaneous     |
   |----------------+-------------------|
   | 8              | System Manager    |
   |----------------+-------------------|
   | 9              | Kernel Developer  |
   +------------------------------------+

13.3. Markup

   Various markup forms and rendering programs have been used for manual
   pages. FreeBSD has used groff(7) and the newer mandoc(1). Most existing
   FreeBSD manual pages, and all new ones, use the mdoc(7) form of markup.
   This is a simple line-based markup that is reasonably expressive. It is
   mostly semantic: parts of text are marked up for what they are, rather
   than for how they should appear when rendered. There is some
   appearance-based markup which is usually best avoided.

   Manual page source is usually interpreted and displayed to the screen
   interactively. The source files can be ordinary text files or compressed
   with gzip(1) to save space.

   Manual pages can also be rendered to other formats, including PostScript
   for printing or PDF generation. See man(1).

  Tip:

   Testing a new manual page can be challenging when it is not located in the
   normal manual page search path. man(1) also does not look in the current
   directory. If the new manual page is in the current directory, prefix the
   filename with a ./:

 % man ./mynewmanpage.8

   An absolute path can also be used:

 % man /home/xsmith/mynewmanpage.8

  13.3.1. Manual Page Sections

   Manual pages are composed of several standard sections. Each section has a
   title in upper case, and the sections for a particular type of manual page
   appear in a specific order. For a category 1 General Command manual page,
   the sections are:

   +------------------------------------------------------------------------+
   | Section Name  |                      Description                       |
   |---------------+--------------------------------------------------------|
   | NAME          | Name of the command                                    |
   |---------------+--------------------------------------------------------|
   | SYNOPSIS      | Format of options and arguments                        |
   |---------------+--------------------------------------------------------|
   | DESCRIPTION   | Description of purpose and usage                       |
   |---------------+--------------------------------------------------------|
   | ENVIRONMENT   | Environment settings that affect operation             |
   |---------------+--------------------------------------------------------|
   | EXIT STATUS   | Error codes returned on exit                           |
   |---------------+--------------------------------------------------------|
   | EXAMPLES      | Examples of usage                                      |
   |---------------+--------------------------------------------------------|
   | COMPATIBILITY | Compatibility with other implementations               |
   |---------------+--------------------------------------------------------|
   | SEE ALSO      | Cross-reference to related manual pages                |
   |---------------+--------------------------------------------------------|
   | STANDARDS     | Compatibility with standards like POSIX                |
   |---------------+--------------------------------------------------------|
   | HISTORY       | History of implementation                              |
   |---------------+--------------------------------------------------------|
   | BUGS          | Known bugs                                             |
   |---------------+--------------------------------------------------------|
   | AUTHORS       | People who created the command or wrote the manual     |
   |               | page.                                                  |
   +------------------------------------------------------------------------+

   Some sections are optional, and the combination of sections for a specific
   type of manual page vary. Examples of the most common types are shown
   later in this chapter.

  13.3.2. Macros

   mdoc(7) markup is based on macros. Lines that begin with a dot contain
   macro commands, each two or three letters long. For example, consider this
   portion of the ls(1) manual page:

 .Dd December 1, 2015  1
 .Dt LS 1
 .Sh NAME  2
 .Nm ls
 .Nd list directory contents
 .Sh SYNOPSIS  3
 .Nm  4
 .Op Fl -libxo  5
 .Op Fl ABCFGHILPRSTUWZabcdfghiklmnopqrstuwxy1,  6
 .Op Fl D Ar format  7
 .Op Ar  8
 .Sh DESCRIPTION  9
 For each operand that names a
 .Ar file
 of a type other than
 directory,
 .Nm
 displays its name as well as any requested,
 associated information.
 For each operand that names a
 .Ar file
 of type directory,
 .Nm
 displays the names of files contained
 within that directory, as well as any requested, associated
 information.

   1 A Document date and Document title are defined.                          
   2 A Section header for the NAME section is defined. Then the Name of the   
     command and a one-line Name description are defined.                     
   3 The SYNOPSIS section begins. This section describes the command-line     
     options and arguments accepted.                                          
   4 Name (.Nm) has already been defined, and repeating it here just displays 
     the defined value in the text.                                           
   5 An Optional Flag called -libxo is shown. The Fl macro adds a dash to the 
     beginning of flags, so this appears in the manual page as --libxo.       
   6 A long list of optional single-character flags are shown.                
   7 An optional -D flag is defined. If the -D flag is given, it must be      
     followed by an Argument. The argument is a format, a string that tells   
     ls(1) what to display and how to display it. Details on the format       
     string are given later in the manual page.                               
   8 A final optional argument is defined. Because no name is specified for   
     the argument, the default of file ... is used.                           
   9 The Section header for the DESCRIPTION section is defined.               

   When rendered with the command man ls, the result displayed on the screen
   looks like this:

 LS(1)                   FreeBSD General Commands Manual                  LS(1)

 NAME
      ls - list directory contents

 SYNOPSIS
      ls [--libxo] [-ABCFGHILPRSTUWZabcdfghiklmnopqrstuwxy1,] [-D format]
         [file ...]

 DESCRIPTION
      For each operand that names a file of a type other than directory, ls
      displays its name as well as any requested, associated information.  For
      each operand that names a file of type directory, ls displays the names
      of files contained within that directory, as well as any requested,
      associated information.

   Optional values are shown inside square brackets.

  13.3.3. Markup Guidelines

   The mdoc(7) markup language is not very strict. For clarity and
   consistency, the FreeBSD Documentation project adds some additional style
   guidelines:

   Only the first letter of macros is upper case

           Always use upper case for the first letter of a macro and lower
           case for the remaining letters.

   Begin new sentences on new lines

           Start a new sentence on a new line, do not begin it on the same
           line as an existing sentence.

   Update .Dd when making non-trivial changes to a manual page

           The Document date informs the reader about the last time the
           manual page was updated. It is important to update whenever
           non-trivial changes are made to the manual pages. Trivial changes
           like spelling or punctuation fixes that do not affect usage can be
           made without updating .Dd.

   Give examples

           Show the reader examples when possible. Even trivial examples are
           valuable, because what is trivial to the writer is not necessarily
           trivial to the reader. Three examples are a good goal. A trivial
           example shows the minimal requirements, a serious example shows
           actual use, and an in-depth example demonstrates unusual or
           non-obvious functionality.

   Include the BSD license

           Include the BSD license on new manual pages. The preferred license
           is available from the Committer's Guide.

  13.3.4. Markup Tricks

   Add a space before punctuation on a line with macros. Example:

 .Sh SEE ALSO
 .Xr geom 4 ,
 .Xr boot0cfg 8 ,
 .Xr geom 8 ,
 .Xr gptboot 8

   Note how the commas at the end of the .Xr lines have been placed after a
   space. The .Xr macro expects two parameters to follow it, the name of an
   external manual page, and a section number. The space separates the
   punctuation from the section number. Without the space, the external links
   would incorrectly point to section 4, or 8,.

  13.3.5. Important Macros

   Some very common macros will be shown here. For more usage examples, see
   mdoc(7), groff_mdoc(7), or search for actual use in /usr/share/man/man*
   directories. For example, to search for examples of the .Bd Begin display
   macro:

 % find /usr/share/man/man* | xargs zgrep '.Bd'

    13.3.5.1. Organizational Macros

   Some macros are used to define logical blocks of a manual page.

   +------------------------------------------------------------------------+
   | Organizational Macro |                       Use                       |
   |----------------------+-------------------------------------------------|
   |                      | Section header. Followed by the name of the     |
   | .Sh                  | section, traditionally all upper case. Think of |
   |                      | these as chapter titles.                        |
   |----------------------+-------------------------------------------------|
   |                      | Subsection header. Followed by the name of the  |
   | .Ss                  | subsection. Used to divide a .Sh section into   |
   |                      | subsections.                                    |
   |----------------------+-------------------------------------------------|
   | .Bl                  | Begin list. Start a list of items.              |
   |----------------------+-------------------------------------------------|
   | .El                  | End a list.                                     |
   |----------------------+-------------------------------------------------|
   | .Bd                  | Begin display. Begin a special area of text,    |
   |                      | like an indented area.                          |
   |----------------------+-------------------------------------------------|
   | .Ed                  | End display.                                    |
   +------------------------------------------------------------------------+

    13.3.5.2. Inline Macros

   Many macros are used to mark up inline text.

   +------------------------------------------------------------------------+
   | Inline Macro |                           Use                           |
   |--------------+---------------------------------------------------------|
   |              | Name. Called with a name as a parameter on the first    |
   | .Nm          | use, then used later without the parameter to display   |
   |              | the name that has already been defined.                 |
   |--------------+---------------------------------------------------------|
   | .Pa          | Path to a file. Used to mark up filenames and directory |
   |              | paths.                                                  |
   +------------------------------------------------------------------------+

13.4. Sample Manual Page Structures

   This section shows minimal desired man page contents for several common
   categories of manual pages.

  13.4.1. Section 1 or 8 Command

   The preferred basic structure for a section 1 or 8 command:

 .Dd August 25, 2017
 .Dt EXAMPLECMD 8
 .Os
 .Sh NAME
 .Nm examplecmd
 .Nd "command to demonstrate section 1 and 8 man pages"
 .Sh SYNOPSIS
 .Nm
 .Op Fl v
 .Sh DESCRIPTION
 The
 .Nm
 utility does nothing except demonstrate a trivial but complete
 manual page for a section 1 or 8 command.
 .Sh SEE ALSO
 .Xr exampleconf 5
 .Sh AUTHORS
 .An Firstname Lastname Aq Mt flastname@example.com

  13.4.2. Section 4 Device Driver

   The preferred basic structure for a section 4 device driver:

 .Dd August 25, 2017
 .Dt EXAMPLEDRIVER 4
 .Os
 .Sh NAME
 .Nm exampledriver
 .Nd "driver to demonstrate section 4 man pages"
 .Sh SYNOPSIS
 To compile this driver into the kernel, add this line to the
 kernel configuration file:
 .Bd -ragged -offset indent
 .Cd "device exampledriver"
 .Ed
 .Pp
 To load the driver as a module at boot, add this line to
 .Xr loader.conf 5 :
 .Bd -literal -offset indent
 exampledriver_load="YES"
 .Ed
 .Sh DESCRIPTION
 The
 .Nm
 driver provides an opportunity to show a skeleton or template
 file for section 4 manual pages.
 .Sh HARDWARE
 The
 .Nm
 driver supports these cards from the aptly-named Nonexistent
 Technologies:
 .Pp
 .Bl -bullet -compact
 .It
 NT X149.2 (single and dual port)
 .It
 NT X149.8 (single port)
 .El
 .Sh DIAGNOSTICS
 .Bl -diag
 .It "flashing green light"
 Something bad happened.
 .It "flashing red light"
 Something really bad happened.
 .It "solid black light"
 Power cord is unplugged.
 .El
 .Sh SEE ALSO
 .Xr example 8
 .Sh HISTORY
 The
 .Nm
 device driver first appeared in
 .Fx 49.2 .
 .Sh AUTHORS
 .An Firstname Lastname Aq Mt flastname@example.com

  13.4.3. Section 5 Configuration File

   The preferred basic structure for a section 5 configuration file:

 .Dd August 25, 2017
 .Dt EXAMPLECONF 5
 .Os
 .Sh NAME
 .Nm example.conf
 .Nd "config file to demonstrate section 5 man pages"
 .Sh DESCRIPTION
 .Nm
 is an example configuration file.
 .Sh SEE ALSO
 .Xr example 8
 .Sh AUTHORS
 .An Firstname Lastname Aq Mt flastname@example.com

13.5. Example Manual Pages to Use as Templates

   Some manual pages are suitable as in-depth examples.

   +--------------------------------------------------------+
   | Manual Page |         Path to Source Location          |
   |-------------+------------------------------------------|
   | cp(1)       | /usr/src/bin/cp/cp.1                     |
   |-------------+------------------------------------------|
   | vt(4)       | /usr/src/share/man/man4/vt.4             |
   |-------------+------------------------------------------|
   | crontab(5)  | /usr/src/usr.sbin/cron/crontab/crontab.5 |
   |-------------+------------------------------------------|
   | gpart(8)    | /usr/src/sbin/geom/class/part/gpart.8    |
   +--------------------------------------------------------+

13.6. Resources

   Resources for manual page writers:

     * man(1)

     * mandoc(1)

     * groff_mdoc(7)

     * Practical UNIX Manuals: mdoc

     * History of UNIX Manpages

                           Chapter 14. Writing Style

   Table of Contents

   14.1. Tips

   14.2. Guidelines

   14.3. Style Guide

   14.4. Word List

14.1. Tips

   Technical documentation can be improved by consistent use of several
   principles. Most of these can be classified into three goals: be clear, be
   complete, and be concise. These goals can conflict with each other. Good
   writing consists of a balance between them.

  14.1.1. Be Clear

   Clarity is extremely important. The reader may be a novice, or reading the
   document in a second language. Strive for simple, uncomplicated text that
   clearly explains the concepts.

   Avoid flowery or embellished speech, jokes, or colloquial expressions.
   Write as simply and clearly as possible. Simple text is easier to
   understand and translate.

   Keep explanations as short, simple, and clear as possible. Avoid empty
   phrases like "in order to", which usually just means "to". Avoid
   potentially patronizing words like "basically". Avoid Latin terms like
   "i.e." or "cf.", which may be unknown outside of academic or scientific
   groups.

   Write in a formal style. Avoid addressing the reader as "you". For
   example, say "copy the file to /tmp" rather than "you can copy the file to
   /tmp".

   Give clear, correct, tested examples. A trivial example is better than no
   example. A good example is better yet. Do not give bad examples,
   identifiable by apologies or sentences like "but really it should never be
   done that way". Bad examples are worse than no examples. Give good
   examples, because even when warned not to use the example as shown, the
   reader will usually just use the example as shown.

   Avoid weasel words like "should", "might", "try", or "could". These words
   imply that the speaker is unsure of the facts, and create doubt in the
   reader.

   Similarly, give instructions as imperative commands: not "you should do
   this", but merely "do this".

  14.1.2. Be Complete

   Do not make assumptions about the reader's abilities or skill level. Tell
   them what they need to know. Give links to other documents to provide
   background information without having to recreate it. Put yourself in the
   reader's place, anticipate the questions they will ask, and answer them.

  14.1.3. Be Concise

   While features should be documented completely, sometimes there is so much
   information that the reader cannot easily find the specific detail needed.
   The balance between being complete and being concise is a challenge. One
   approach is to have an introduction, then a "quick start" section that
   describes the most common situation, followed by an in-depth reference
   section.

14.2. Guidelines

   To promote consistency between the myriad authors of the FreeBSD
   documentation, some guidelines have been drawn up for authors to follow.

   Use American English Spelling

           There are several variants of English, with different spellings
           for the same word. Where spellings differ, use the American
           English variant. "color", not "colour", "rationalize", not
           "rationalise", and so on.

  Note:

           The use of British English may be accepted in the case of a
           contributed article, however the spelling must be consistent
           within the whole document. The other documents such as books, web
           site, manual pages, etc. will have to use American English.

   Do not use contractions

           Do not use contractions. Always spell the phrase out in full.
           "Don't use contractions" is wrong.

           Avoiding contractions makes for a more formal tone, is more
           precise, and is slightly easier for translators.

   Use the serial comma

           In a list of items within a paragraph, separate each item from the
           others with a comma. Separate the last item from the others with a
           comma and the word "and".

           For example:

             This is a list of one, two and three items.

           Is this a list of three items, "one", "two", and "three", or a
           list of two items, "one" and "two and three"?

           It is better to be explicit and include a serial comma:

             This is a list of one, two, and three items.

   Avoid redundant phrases

           Do not use redundant phrases. In particular, "the command", "the
           file", and "man command" are often redundant.

           For example, commands:

           Wrong: Use the svn command to update sources.

           Right: Use svn to update sources.

           Filenames:

           Wrong: ... in the filename /etc/rc.local...

           Right: ... in /etc/rc.local...

           Manual page references (the second example uses citerefentry with
           the &man.csh.1; entity):.

           Wrong: See man csh for more information.

           Right: See csh(1).

   Two spaces between sentences

           Always use two spaces between sentences, as it improves
           readability and eases use of tools such as Emacs.

           A period and spaces followed by a capital letter does not always
           mark a new sentence, especially in names. "Jordan K. Hubbard" is a
           good example. It has a capital H following a period and a space,
           and is certainly not a new sentence.

   For more information about writing style, see Elements of Style, by
   William Strunk.

14.3. Style Guide

   To keep the source for the documentation consistent when many different
   people are editing it, please follow these style conventions.

  14.3.1. Letter Case

   Tags are entered in lower case, para, not PARA.

   Text that appears in SGML contexts is generally written in upper case,
   <!ENTITY...>, and <!DOCTYPE...>, not <!entity...> and <!doctype...>.

  14.3.2. Acronyms

   Acronyms should be defined the first time they appear in a document, as
   in: "Network Time Protocol (NTP)". After the acronym has been defined, use
   the acronym alone unless it makes more sense contextually to use the whole
   term. Acronyms are usually defined only once per chapter or per document.

   All acronyms should be enclosed in acronym tags.

  14.3.3. Indentation

   The first line in each file starts with no indentation, regardless of the
   indentation level of the file which might contain the current file.

   Opening tags increase the indentation level by two spaces. Closing tags
   decrease the indentation level by two spaces. Blocks of eight spaces at
   the start of a line should be replaced with a tab. Do not use spaces in
   front of tabs, and do not add extraneous whitespace at the end of a line.
   Content within elements should be indented by two spaces if the content
   runs over more than one line.

   For example, the source for this section looks like this:

 <chapter>
   <title>...</title>

   <sect1>
     <title>...</title>

     <sect2>
       <title>Indentation</title>

       <para>The first line in each file starts with no indentation,
         <emphasis>regardless</emphasis> of the indentation level of
         the file which might contain the current file.</para>

       ...
     </sect2>
   </sect1>
 </chapter>

   Tags containing long attributes follow the same rules. Following the
   indentation rules in this case helps editors and writers see which content
   is inside the tags:

 <para>See the <link
     linkend="gmirror-troubleshooting">Troubleshooting</link>
   section if there are problems booting.  Powering down and
   disconnecting the original <filename>ada0</filename> disk
   will allow it to be kept as an offline backup.</para>

 <para>It is also possible to journal the boot disk of a &os;
   system.  Refer to the article <link
     xlink:href="&url.articles.gjournal-desktop;">Implementing UFS
     Journaling on a Desktop PC</link> for detailed
   instructions.</para>

   When an element is too long to fit on the remainder of a line without
   wrapping, moving the start tag to the next line can make the source easier
   to read. In this example, the systemitem element has been moved to the
   next line to avoid wrapping and indenting:

 <para>With file flags, even
   <systemitem class="username">root</systemitem> can be
   prevented from removing or altering files.</para>

   Configurations to help various text editors conform to these guidelines
   can be found in Chapter 15, Editor Configuration.

  14.3.4. Tag Style

    14.3.4.1. Tag Spacing

   Tags that start at the same indent as a previous tag should be separated
   by a blank line, and those that are not at the same indent as a previous
   tag should not:

 <article lang='en'>
   <articleinfo>
     <title>NIS</title>

     <pubdate>October 1999</pubdate>

     <abstract>
       <para>...
         ...
         ...</para>
     </abstract>
   </articleinfo>

   <sect1>
     <title>...</title>

     <para>...</para>
   </sect1>

   <sect1>
     <title>...</title>

     <para>...</para>
   </sect1>
 </article>

    14.3.4.2. Separating Tags

   Tags like itemizedlist which will always have further tags inside them,
   and in fact do not take character data themselves, are always on a line by
   themselves.

   Tags like para and term do not need other tags to contain normal character
   data, and their contents begin immediately after the tag, on the same
   line.

   The same applies to when these two types of tags close.

   This leads to an obvious problem when mixing these tags.

   When a starting tag which cannot contain character data directly follows a
   tag of the type that requires other tags within it to use character data,
   they are on separate lines. The second tag should be properly indented.

   When a tag which can contain character data closes directly after a tag
   which cannot contain character data closes, they co-exist on the same
   line.

  14.3.5. Whitespace Changes

   Do not commit changes to content at the same time as changes to
   formatting.

   When content and whitespace changes are kept separate, translation teams
   can easily see whether a change was content that must be translated or
   only whitespace.

   For example, if two sentences have been added to a paragraph so that the
   line lengths now go over 80 columns, first commit the change with the
   too-long lines. Then fix the line wrapping, and commit this second change.
   In the commit message for the second change, indicate that this is a
   whitespace-only change that can be ignored by translators.

  14.3.6. Non-Breaking Space

   Avoid line breaks in places where they look ugly or make it difficult to
   follow a sentence. Line breaks depend on the width of the chosen output
   medium. In particular, viewing the HTML documentation with a text browser
   can lead to badly formatted paragraphs like the next one:

 Data capacity ranges from 40 MB to 15
 GB.  Hardware compression ...

   The general entity &nbsp; prohibits line breaks between parts belonging
   together. Use non-breaking spaces in the following places:

     * between numbers and units:

 57600&nbsp;bps

     * between program names and version numbers:

 &os;&nbsp;9.2

     * between multiword names (use with caution when applying this to more
       than 3-4 word names like "The FreeBSD Brazilian Portuguese
       Documentation Project"):

 Sun&nbsp;Microsystems

14.4. Word List

   This list of words shows the correct spelling and capitalization when used
   in FreeBSD documentation. If a word is not on this list, ask about it on
   the FreeBSD documentation project mailing list.

      Word                   XML Code                         Notes           
   CD-ROM      <acronym>CD-ROM</acronym>                                      
   DoS (Denial <acronym>DoS</acronym>                                         
   of Service) 
   email                                                                      
   file system                                                                
   IPsec                                                                      
   Internet                                                                   
   manual page                                                                
   mail server                                                                
   name server                                                                
   Ports                                                                      
   Collection  
   read-only                                                                  
   Soft                                                                       
   Updates     
   stdin       <varname>stdin</varname>                                       
   stdout      <varname>stdout</varname>                                      
   stderr      <varname>stderr</varname>                                      
                                                     Do not refer to the      
                                                     Subversion application   
   Subversion  <application>Subversion</application> as SVN in upper case. To 
                                                     refer to the command,    
                                                     use                      
                                                     <command>svn</command>.  
   UNIX(R)     &unix;                                                         
                                                     things that apply to     
   userland                                          user space, not the      
                                                     kernel                   
   web server                                                                 

                        Chapter 15. Editor Configuration

   Table of Contents

   15.1. Vim

   15.2. Emacs

   15.3. nano

   Adjusting text editor configuration can make working on document files
   quicker and easier, and help documents conform to FDP guidelines.

15.1. Vim

   Install from editors/vim or editors/vim-lite, then follow the
   configuration instructions in Section 15.1.2, "Configuration".

  15.1.1. Use

   Press P to reformat paragraphs or text that has been selected in Visual
   mode. Press T to replace groups of eight spaces with a tab.

  15.1.2. Configuration

   Edit ~/.vimrc, adding these lines to the end of the file:

 if has("autocmd")
     au BufNewFile,BufRead *.sgml,*.ent,*.xsl,*.xml call Set_SGML()
     au BufNewFile,BufRead *.[1-9] call ShowSpecial()
 endif " has(autocmd)

 function Set_Highlights()
     "match ExtraWhitespace /^\s* \s*\|\s\+$/
     highlight default link OverLength ErrorMsg
     match OverLength /\%71v.\+/
     return 0
 endfunction

 function ShowSpecial()
     setlocal list listchars=tab:>>,trail:*,eol:$
     hi def link nontext ErrorMsg
     return 0
 endfunction " ShowSpecial()

 function Set_SGML()
     setlocal number
     syn match sgmlSpecial "&[^;]*;"
     setlocal syntax=sgml
     setlocal filetype=xml
     setlocal shiftwidth=2
     setlocal textwidth=70
     setlocal tabstop=8
     setlocal softtabstop=2
     setlocal formatprg="fmt -p"
     setlocal autoindent
     setlocal smartindent
     " Rewrap paragraphs
     noremap P gqj
     " Replace spaces with tabs
     noremap T :s/        /\t/<CR>
     call ShowSpecial()
     call Set_Highlights()
     return 0
 endfunction " Set_SGML()

15.2. Emacs

   Install from editors/emacs or editors/emacs-devel.

  15.2.1. Validation

   Emacs's nxml-mode uses compact relax NG schemas for validating XML. A
   compact relax NG schema for FreeBSD's extension to DocBook 5.0 is included
   in the documentation repository. To configure nxml-mode to validate using
   this schema, create ~/.emacs.d/schema/schemas.xml and add these lines to
   the file:

 <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0">
   <documentElement localName="section" typeId="DocBook">
   <documentElement localName="chapter" typeId="DocBook">
   <documentElement localName="article" typeId="DocBook">
   <documentElement localName="book" typeId="DocBook">
   <typeId id="DocBook" uri="/usr/local/share/xml/docbook/5.0/rng/docbook.rnc">
 </locatingRules>

  15.2.2. Automated Proofreading with Flycheck and Igor

   The Flycheck package is available from Milkypostman's Emacs Lisp Package
   Archive (MELPA). If MELPA is not already in Emacs's packages-archives, it
   can be added by evaluating

 (add-to-list 'package-archives '("melpa" . "http://stable.melpa.org/packages/") t)

   Add the line to Emacs's initialization file (one of ~/.emacs, ~/.emacs.el,
   or ~.emacs.d/init.el) to make this change permanent.

   To install Flycheck, evaluate

 (package-install 'flycheck)

   Create a Flycheck checker for textproc/igor by evaluating

 (flycheck-define-checker igor
   "FreeBSD Documentation Project sanity checker.

 See URLs https://www.freebsd.org/docproj/ and
 http://www.freshports.org/textproc/igor/."
   :command ("igor" "-X" source-inplace)
   :error-parser flycheck-parse-checkstyle
   :modes (nxml-mode)
   :standard-input t)

   (add-to-list 'flycheck-checkers 'igor 'append)

   Again, add these lines to Emacs's initialization file to make the changes
   permanent.

  15.2.3. FreeBSD Documentation Specific Settings

   To apply settings specific to the FreeBSD documentation project, create
   .dir-locals.el in the root directory of the documentation repository and
   add these lines to the file:

 ;;; Directory Local Variables
 ;;; For more information see (info "(emacs) Directory Variables")

 ((nxml-mode
   (eval . (turn-on-auto-fill))
   (fill-column . 70)
   (eval . (require 'flycheck))
   (eval . (flycheck-mode 1))
   (flycheck-checker . igor)
   (eval . (add-to-list 'rng-schema-locating-files "~/.emacs.d/schema/schemas.xml"))))

15.3. nano

   Install from editors/nano or editors/nano-devel.

  15.3.1. Configuration

   Copy the sample XML syntax highlight file to the user's home directory:

 % cp /usr/local/share/nano/xml.nanorc ~/.nanorc

   Use an editor to replace the lines in the ~/.nanorc syntax "xml" block
   with these rules:

 syntax "xml" "\.([jrs]html?|xml|xslt?)$"
 # trailing whitespace
 color ,blue "[[:space:]]+$"
 # multiples of eight spaces at the start a line
 # (after zero or more tabs) should be a tab
 color ,blue "^([TAB]*[ ]{8})+"
 # tabs after spaces
 color ,yellow "( )+TAB"
 # highlight indents that have an odd number of spaces
 color ,red "^(([ ]{2})+|(TAB+))*[ ]{1}[^ ]{1}"
 # lines longer than 70 characters
 color ,yellow "^(.{71})|(TAB.{63})|(TAB{2}.{55})|(TAB{3}.{47}).+$"

   Process the file to create embedded tabs:

 % perl -i'' -pe 's/TAB/\t/g' ~/.nanorc

  15.3.2. Use

   Specify additional helpful options when running the editor:

 % nano -AKipwz -r 70 -T8 chapter.xml

   Users of csh(1) can define an alias in ~/.cshrc to automate these options:

 alias nano "nano -AKipwz -r 70 -T8"

   After the alias is defined, the options will be added automatically:

 % nano chapter.xml

                              Chapter 16. See Also

   Table of Contents

   16.1. The FreeBSD Documentation Project

   16.2. XML

   16.3. HTML

   16.4. DocBook

   This document is deliberately not an exhaustive discussion of XML, the
   DTDs listed, and the FreeBSD Documentation Project. For more information
   about these, you are encouraged to see the following web sites.

16.1. The FreeBSD Documentation Project

     * The FreeBSD Documentation Project web pages

     * The FreeBSD Handbook

16.2. XML

     * W3C's XML page SGML/XML web page

16.3. HTML

     * The World Wide Web Consortium

     * The HTML 4.0 specification

16.4. DocBook

     * The DocBook Technical Committee, maintainers of the DocBook DTD

     * DocBook: The Definitive Guide, the online documentation for the
       DocBook DTD

     * The DocBook Open Repository contains DSSSL stylesheets and other
       resources for people using DocBook

                              Appendix A. Examples

   Table of Contents

   A.1. DocBook book

   A.2. DocBook article

   These examples are not exhaustive-they do not contain all the elements
   that might be desirable to use, particularly in a document's front matter.
   For more examples of DocBook markup, examine the XML source for this and
   other documents available in the Subversion doc repository, or available
   online starting at http://svnweb.FreeBSD.org/doc/.

A.1. DocBook book

   Example A.1. DocBook book

 <!DOCTYPE book PUBLIC "-//FreeBSD//DTD DocBook XML V5.0-Based Extension//EN"
         "http://www.FreeBSD.org/XML/share/xml/freebsd50.dtd">

 <book xmlns="http://docbook.org/ns/docbook"
   xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
   xml:lang="en">

   <info>
     <title>An Example Book</title>

     <author>
       <personname>
         <firstname>Your first name</firstname>
         <surname>Your surname</surname>
       </personname>

       <affiliation>
         <address>
           <email>foo@example.com</email>
         </address>
       </affiliation>
     </author>

     <copyright>
       <year>2000</year>
       <holder>Copyright string here</holder>
     </copyright>

     <abstract>
       <para>If your book has an abstract then it should go here.</para>
     </abstract>
   </info>

   <preface>
     <title>Preface</title>

     <para>Your book may have a preface, in which case it should be placed
       here.</para>
   </preface>

   <chapter>
     <title>My First Chapter</title>

     <para>This is the first chapter in my book.</para>

     <sect1>
       <title>My First Section</title>

       <para>This is the first section in my book.</para>
     </sect1>
   </chapter>
 </book>

A.2. DocBook article

   Example A.2. DocBook article

 <!DOCTYPE article PUBLIC "-//FreeBSD//DTD DocBook XML V5.0-Based Extension//EN"
         "http://www.FreeBSD.org/XML/share/xml/freebsd50.dtd">

 <article xmlns="http://docbook.org/ns/docbook"
   xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
   xml:lang="en">

   <info>
     <title>An Example Article</title>

     <author>
       <personname>
         <firstname>Your first name</firstname>
         <surname>Your surname</surname>
       </personname>

       <affiliation>
         <address>
           <email>foo@example.com</email>
         </address>
       </affiliation>
     </author>

     <copyright>
       <year>2000</year>
       <holder>Copyright string here</holder>
     </copyright>

     <abstract>
       <para>If your article has an abstract then it should go here.</para>
     </abstract>
   </info>

   <sect1>
     <title>My First Section</title>

     <para>This is the first section in my article.</para>

     <sect2>
       <title>My First Sub-Section</title>

       <para>This is the first sub-section in my article.</para>
     </sect2>
   </sect1>
 </article>

                                     Index

  F

   Formal Public Identifier, The DOCTYPE Declaration, Formal Public
   Identifiers (FPIs)
