Pod is a deceptively simple format; it is easy to learn and very straightforward to use, but it is
suprisingly expressive. Nevertheless, it is not nearly as expressive or complex as DocBook. In most
cases, given some Pod, the analogous DocBook markup is obvious, but not always. This section describes
how Pod::2::DocBook treats Pod input so that Pod authors may make informed choices. In every case,
Pod::2::DocBook strives to make easy things easy and hard things possible.
The primary motivation behind Pod::2::DocBook is to facilitate single-source publishing. That is, you
should be able to generate man pages, web pages, PDF and PostScript documents, or any other format your
SGML and/or Pod tools can produce, from the same Pod source, without the need for hand-editing any
intermediate files. This may not always be possible, or you may simply choose to render Pod to DocBook
and use that as your single source. To satisfy the first requirement, Pod::2::DocBook always processes
the entire Pod source and tries very hard to produce valid DocBook markup, even in the presence of
malformed Pod (see "DIAGNOSTICS"). To satisfy the second requirement (and to be a little nifty),
Pod::2::DocBook pretty-prints its output. If you're curious about what specific output to expect, read
on.
DocumentTypes
DocBook's structure is very modular; many of its document types can be embedded directly into other
documents. Accordingly, Pod::2::DocBook will generate four different document types: article, chapter,
refentry, and section. This makes it easy, for instance, to write all the chapters of a book in separate
Pod documents, translate them into DocBook markup and later glue them together before processing the
entire book. You could do the same with each section in an article, or you could write the entire
article in a single Pod document. Other document types, such as book and set, do not map easily from
Pod, because they require structure for which there is no Pod equivalent. But given sections and
chapters, making larger documents becomes much simpler.
The refentry document type is a little different from the others. Sections, articles, and chapters are
essentially composed of nested sections. But a refentry has specialized elements for the NAME and
SYNOPSIS sections. To accommodate this, Pod::2::DocBook performs extra processing on the Pod source when
the doctype is set to refentry. You probably don't have to do anything to your document to assist the
processing; typical man page conventions cover the requirements. Just make sure that the NAME and
SYNOPSIS headers are both =head1s, that "NAME" and "SYNOPSIS" are both uppercase, and that =head1NAME is
the first line of Pod source.
OrdinaryParagraphs
Ordinary paragraphs in a Pod document translate naturally to DocBook paragraphs. Specifically, after any
formatting codes are processed, the characters "<", ">" and "&" are translated to their respective SGML
character entities, and the paragraph is wrapped in <para> and </para>.
For example, given this Pod paragraph:
Here is some text with I<italics> & an ampersand.
Pod::2::DocBook would produce DocBook markup similar to this:
<para>
Here is some text with <emphasis role="italic">italics</emphasis>
& an ampersand.
</para>
Depending on your final output format, you may sometimes want double quotes in ordinary paragraphs to
show up ultimately as "smart quotes" (little 66s and 99s). Pod::2::DocBook offers a convenient mechanism
for handling double quotes in ordinary paragraphs and letting your SGML toolchain manage their
presentation: the fix_double_quotes option to "new()". If this option is set to a true value,
Pod::2::DocBook will replace pairs of double quotes in ordinary paragraphs (and only in ordinary
paragraphs) with <quote> and </quote>.
For example, given this Pod paragraph:
Here is some text with I<italics> & an "ampersand".
Pod::2::DocBook, with fix_double_quotes set, would produce DocBook markup similar to this:
<para>
Here is some text with <emphasis role="italic">italics</emphasis>
& an <quote>ampersand</quote>.
</para>
If you have a paragraph with an odd number of double quotes, the last one will be left untouched, which
may or may not be what you want. If you have such a document, replace the unpaired double quote
character with E<quot>, and Pod::2::DocBook should be able to give you the output you expect. Also, if
you have any =begindocbook ... =enddocbook regions (see "Embedded DocBook Markup") in your Pod, you are
responsible for managing your own quotes in those regions.
VerbatimParagraphs
Verbatim paragraphs translate even more naturally; perlpodspec mandates that absolutely no processing
should be performed on them. So Pod::2::DocBook simply marks them as CDATA and wraps them in <screen>
and </screen>. They are not indented the way ordinary paragraphs are, because they treat whitespace as
significant.
For example, given this verbatim paragraph (imagine there's leading whitespace in the source):
my $i = 10;
while (<> && $i--) {
print "$i: $_";
}
Pod::2::DocBook would produce DocBook markup similar to this:
<screen><![CDATA[my $i = 10;
while (<> && $i--) {
print "$i: $_";
}]] ></screen>
Multiple contiguous verbatim paragraphs are treated as a single screen element, with blank lines
separating the paragraphs, as dictated by perlpodspec.
CommandParagraphs
"=head1 Heading Text"
"=head2 Heading Text"
"=head3 Heading Text"
"=head4 Heading Text"
All of the Pod heading commands produce DocBook section elements, with the heading text as titles.
Pod::2::DocBook (perlpod) only allows for 4 heading levels, but DocBook allows arbitrary nesting; see
"Embedded DocBook Markup" if you need more than 4 levels. Pod::2::DocBook only looks at relative
heading levels to determine nesting. For example, this bit of Pod:
=head1 1
Contents of section 1
=head2 1.1
Contents of section 1.1
and this bit of Pod:
=head1 1
Contents of section 1
=head3 1.1
Contents of section 1.1
both produce the same DocBook markup, which will look something like this:
<section id="article-My-Article-1"><title>1</title>
<para>
Contents of section 1
</para>
<section id="article-My-Article-1-1"><title>1.1</title>
<para>
Contents of section 1.1
</para>
</section>
</section>
Note that Pod::2::DocBook automatically generates section identifiers from your doctype, document
title and section title. It does the same when you make internal links (see "Formatting Codes",
ensuring that if you supply the same link text as you did for the section title, the resulting
identifiers will be the same.
"=over indentlevel"
"=item stuff..."
"=back"
"=over" ... "=back" regions are somewhat complex, in that they can lead to a variety of DocBook
constructs. In every case, indentlevel is ignored by Pod::2::DocBook, since that's best left to your
stylesheets.
An "=over" ... "=back" region with no "=item"s represents indented text and maps directly to a
DocBook blockquote element. Given this source:
=over 4
This text should be indented.
=back
Pod::2::DocBook will produce DocBook markup similar to this:
<blockquote>
<para>
This text should be indented.
</para>
</blockquote>
Inside an "=over" ... "=back" region, "=item" commands generate lists. The text that follows the
first "=item" determines the type of list that will be output:
• "*" (an asterisk) produces <itemizedlist>
• "1" or "1." produces <orderedlistnumeration="arabic">
• "a" or "a." produces <orderedlistnumeration="loweralpha">
• "A" or "A." produces <orderedlistnumeration="upperalpha">
• "i" or "i." produces <orderedlistnumeration="lowerroman">
• "I" or "I." produces <orderedlistnumeration="upperroman">
• anything else produces <variablelist>
Since the output from each of these is relatively verbose, the best way to see examples is to
actually render some Pod into DocBook.
"=pod"
"=cut"
Pod::Parser recognizes these commands, and, therefore, so does Pod::2::DocBook, but they don't
produce any output.
"=begin formatname"
"=end formatname"
"=for formatname text..."
Pod::2::DocBook supports two formats: docbook, explained in "Embedded DocBook Markup", and table,
explained in "Simple Tables".
"=encoding encodingname"
This command is currently not supported. If Pod::2::DocBook encounters a document that contains
"=encoding", it will ignore the command and report an error ("unknown command `%s' at line %d in file
%s").
EmbeddedDocBookMarkup
There are a wide range of DocBook structures for which there is no Pod equivalent. For these, you will
have to provide your own markup using =begindocbook ... =enddocbook or =fordocbook....
Pod::2::DocBook will directly output whatever text you provide, unprocessed, so it's up to you to ensure
that it's valid DocBook.
Images, footnotes and many inline elements are obvious candidates for embedded markup. Another possible
use is nesting sections more than four-deep. For example, given this source:
=head1 1
This is Section 1
=head2 1.1
This is Section 1.1
=head3 1.1.1
This is Section 1.1.1
=head4 1.1.1.1
This is Section 1.1.1.1
=begin docbook
<section>
<title>1.1.1.1.1</title>
<para>This is Section 1.1.1.1.1</para>
</section>
=end docbook
Pod::2::DocBook will generate DocBook markup similar to this:
<section id="article-My-Article-1"><title>1</title>
<para>
This is Section 1
</para>
<section id="article-My-Article-1-1"><title>1.1</title>
<para>
This is Section 1.1
</para>
<section id="article-My-Article-1-1-1"><title>1.1.1</title>
<para>
This is Section 1.1.1
</para>
<section id="article-My-Article-1-1-1-1"><title>1.1.1.1</title>
<para>
This is Section 1.1.1.1
</para>
<section>
<title>1.1.1.1.1</title>
<para>This is Section 1.1.1.1.1</para>
</section>
</section>
</section>
</section>
</section>
SimpleTables
Pod::2::DocBook also provides a mechanism for generating basic tables with =begintable and =enddocbook.
If you have simple tabular data or a CSV file exported from some application, Pod::2::DocBook makes it
easy to generate a table from your data. The syntax is intended to be simple, so DocBook's entire table
feature set is not represented, but even if you do need more complex table markup than Pod::2::DocBook
produces, you can rapidly produce some markup which you can hand-edit and then embed directly in your Pod
with =begindocbook ... =enddocbook. Each table definition spans multiple lines, so there is no
equivalent =fortable command.
The first line of a table definition gives the table's title. The second line gives a list of comma-
separated column specifications (really just column alignments), each of which can be left, center or
right. The third line is a list of comma-separated column headings, and every subsequent line consists
of comma-separated row data. If any of your data actually contain commas, you can enclose them in double
quotes; if they also contain double quotes, you must escape the inner quotes with backslashes (typical
CSV stuff).
Here's an example:
=begin table
Sample Table
left,center,right
Powers of Ten,Planets,Dollars
10,Earth,$1
100,Mercury,$5
1000,Mars,$10
10000,Venus,$20
100000,"Jupiter, Saturn",$50
=end table
And here's what Pod::2::DocBook would do with it:
<table>
<title>Sample Table</title>
<tgroup cols="3">
<colspec align="left">
<colspec align="center">
<colspec align="right">
<thead>
<row>
<entry>Powers of Ten</entry>
<entry>Planets</entry>
<entry>Dollars</entry>
</row>
</thead>
<tbody>
<row>
<entry>10</entry>
<entry>Earth</entry>
<entry>$1</entry>
</row>
<row>
<entry>100</entry>
<entry>Mercury</entry>
<entry>$5</entry>
</row>
<row>
<entry>1000</entry>
<entry>Mars</entry>
<entry>$10</entry>
</row>
<row>
<entry>10000</entry>
<entry>Venus</entry>
<entry>$20</entry>
</row>
<row>
<entry>100000</entry>
<entry>Jupiter, Saturn</entry>
<entry>$50</entry>
</row>
</tbody>
</tgroup>
</table>
FormattingCodes
Pod formatting codes render directly into DocBook as inline elements:
• "I<text>"
<emphasis role="italic">text</emphasis>
• "B<text>"
<emphasis role="bold">text</emphasis>
• "C<code>"
<literal role="code"><![CDATA[code]] ></literal>
• "L<name>"
<citerefentry><refentrytitle>name</refentrytitle></citerefentry>
• "L<name(n)>"
<citerefentry><refentrytitle>name</refentrytitle>
<manvolnum>n</manvolnum></citerefentry>
• "L<name/"sec">" or "L<name/sec>"
<quote>sec</quote> in <citerefentry>
<refentrytitle>name</refentrytitle></citerefentry>
• "L<name(n)/"sec">" or "L<name(n)/sec>"
<quote>sec</quote> in <citerefentry>
<refentrytitle>name</refentrytitle><manvolnum>n</manvolnum>
</citerefentry>
• "L</"sec">" or "L</sec>" or "L<"sec">"
<link linkend="article-My-Article-sec"><quote>sec</quote></link>
• "L<text|name>"
text
• "L<text|name/"sec">" or "L<text|name/sec>"
text
• "L<text|/"sec">" or "L<text|/sec>" or "L<text|"sec">"
<link linkend="article-My-Article-sec"><quote>text</quote></link>
• "L<scheme:...>"
<ulink url="scheme:...">scheme:...</ulink>
• "E<verbar>"
|
• "E<sol>"
/
• "E<number>"
&#number;
• any other "E<escape>"
&escape;
• "F<filename>"
<filename>filename</filename>
• "S<text with spaces>"
text with spaces
• "X<topic name>"
<indexterm><primary>topic name</primary></indexterm>
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