Patch for pod/perlpod.pod

[perl5.git] / pod / perlpod.pod

=head1 NAME

perlpod - plain old documentation

=head1 DESCRIPTION

A pod-to-whatever translator reads a pod file paragraph by paragraph,
and translates it to the appropriate output format.  There are
three kinds of paragraphs:

=over 4

=item *

A verbatim paragraph, distinguished by being indented (that is,
it starts with space or tab).  It should be reproduced exactly,
with tabs assumed to be on 8-column boundaries.  There are no
special formatting escapes, so you can't italicize or anything
like that.  A \ means \, and nothing else.

=item *

A command.  All command paragraphs start with "=", followed by an
identifier, followed by arbitrary text that the command can
use however it pleases.  Currently recognized commands are

    =head1 heading
    =head2 heading
    =item text
    =over N
    =back
    =cut
    =pod

The "=pod" directive does nothing beyond telling the compiler to lay
off of through the next "=cut".  It's useful for adding another 
paragraph to the doc if you're mixing up code and pod a lot.  

Head1 and head2 produce first and second level headings, with the text on
the same paragraph as "=headn" forming the heading description.

Item, over, and back require a little more explanation: Over starts a
section specifically for the generation of a list using =item commands. At
the end of your list, use =back to end it. You will probably want to give
"4" as the number to =over, as some formatters will use this for indentation.
This should probably be a default. Note also that there are some basic rules
to using =item: don't use them outside of an =over/=back block, use at least
one inside an =over/=back block, you don't _have_ to include the =back if
the list just runs off the document, and perhaps most importantly, keep the
items consistent: either use "=item *" for all of them, to produce bullets,
or use "=item 1.", "=item 2.", etc., to produce numbered lists, or use
"=item foo", "=item bar", etc., i.e., things that looks nothing like bullets
or numbers. If you start with bullets or numbers, stick with them, as many
formatters use the first =item type to decide how to format the list.  

And don't forget, when using any command, that that command lasts up until
the end of the B<paragraph>, not the line. Hence in the examples below, you
can see the blank lines after each command to end its paragraph.

Some examples of lists include:

 =over 4

 =item *

 First item

 =item *

 Second item

 =back

 =over 4

 =item Foo()

 Description of Foo function

 =item Bar()

 Description of Bar function

 =back

=item *

An ordinary block of text.  It will be filled, and maybe even
justified.  Certain interior sequences are recognized both
here and in commands:

    I<text>     italicize text, used for emphasis or variables
    B<text>     embolden text, used for switches and programs
    S<text>     text contains non-breaking spaces
    C<code>	literal code 
    L<name>     A link (cross reference) to name
		    L<name>		manpage
		    L<name/ident>	item in manpage
		    L<name/"sec">	section in other manpage
		    L<"sec">		section in this manpage
					(the quotes are optional)
		    L</"sec">		ditto
    F<file>	Used for filenames
    X<index>	An index entry
    Z<>         A zero-width character
    E<escape>   An HTML escape
		    E<lt>		A literal <
		    E<gt>		A literal >
		    (these are optional except in other interior
		     sequences and when preceded by a capital letter)
		    E<nnn>		Character number nnn.

=back

That's it.  The intent is simplicity, not power.  I wanted paragraphs
to look like paragraphs (block format), so that they stand out
visually, and so that I could run them through fmt easily to reformat
them (that's F7 in my version of B<vi>).  I wanted the translator (and not
me) to worry about whether " or ' is a left quote or a right quote
within filled text, and I wanted it to leave the quotes alone dammit in
verbatim mode, so I could slurp in a working program, shift it over 4
spaces, and have it print out, er, verbatim.  And presumably in a
constant width font.

In particular, you can leave things like this verbatim in your text:

    Perl
    FILEHANDLE
    $variable
    function()
    manpage(3r)

Doubtless a few other commands or sequences will need to be added along
the way, but I've gotten along surprisingly well with just these.

Note that I'm not at all claiming this to be sufficient for producing a
book.  I'm just trying to make an idiot-proof common source for nroff,
TeX, and other markup languages, as used for online documentation.
Translators exist for B<pod2man>  (that's for nroff(1) and troff(1)),
B<pod2html>, B<pod2latex>, and B<pod2fm>.

=head1 Embedding Pods in Perl Modules

You can embed pod documentation in your Perl scripts.  Start your
documentation with a =head1 command at the beg, and end it with 
an =cut command.  Perl will ignore the pod text.  See any of the
supplied library modules for examples.  If you're going to put
your pods at the end of the file, and you're using an __END__
or __DATA__ cut mark, make sure to put a blank line there before
the first pod directive.

    __END__

    =head1 NAME

    modern - I am a modern module

If you had not had that blank line there, then the translators wouldn't
have seen it.

=head1 Common Pod Pitfalls

=over 4

=item *

Pod translators usually will require paragraphs to be separated by
completely empty lines.  If you have an apparently blank line with
some spaces on it, this can cause odd formatting.

=item *

Translators will mostly add wording around a LE<lt>E<gt> link, so that
C<LE<lt>foo(1)E<gt>> becomes "the I<foo>(1) manpage", for example (see
B<pod2man> for details).  Thus, you shouldn't write things like C<the
LE<lt>fooE<gt> manpage>, if you want the translated document to read
sensibly.

=item *

The script F<pod/checkpods.PL> in the Perl source distribution
provides skeletal checking for lines that look blank but aren't
B<only>, but is there as a placeholder until someone writes
Pod::Checker.  The best way to check your pod is to pass it through
one or more translators and proofread the result, or print out the
result and proofread that.  Some of the problems found may be bugs in
the translators, which you may or may not wish to work around.

=back

=head1 SEE ALSO

L<pod2man> and L<perlsyn/"PODs: Embedded Documentation">

=head1 AUTHOR

Larry Wall