Update IO-Compress to CPAN version 2.040

[perl5.git] / pod / perlpodstyle.pod

=head1 NAME

perlpodstyle - Perl POD style guide

=head1 DESCRIPTION

These are general guidelines for how to write POD documentation for Perl
scripts and modules, based on general guidelines for writing good Unix man
pages.  All of these guidelines are, of course, optional, but following
them will make your documentation more consistent with other documentation
on the system.

Here are some simple guidelines for markup; see L<perlpod> for details.

=over

=item bold (BE<lt>E<gt>)

B<NOTE: Use extremely rarely.>  Do I<not> use bold for emphasis; that's
what italics are for.  Restrict bold for notices like B<NOTE:> and
B<WARNING:>.  However, program arguments and options--but I<not> their
names!--are written in bold (using BE<lt>E<gt>) to distinguish the B<-f>
command-line option from the C<-f> filetest operator.

=item italic (IE<lt>E<gt>)

Use italic to emphasize text, like I<this>.  Function names are
traditionally written in italics; if you write a function as function(),
Pod::Man will take care of this for you.  Names of programs, including the
name of the program being documented, are conventionally written in italics
(using IE<lt>E<gt>) wherever they occur in normal roman text.

=item code (CE<lt>E<gt>)

Literal code should be in CE<lt>E<gt>.  However metasyntactic placeholders
should furthermore be nested in "italics" (actually, oblique) like
CE<lt>IE<lt>E<gt>E<gt>.  That way
CE<lt>accept(IE<lt>NEWSOCKETE<gt>, E<lt>GENERICSOCKETE<gt>)E<gt>
renders as C<accept(I<NEWSOCKET>, I<GENERICSOCKET>)>.

=item files (FE<lt>E<gt>)

Filenames, whether absolute or relative, are specified with the FE<lt>E<gt>
markup. This will render as italics, but has other semantic connotations.

=back

References to other man pages should be in the form "manpage(section)" or
"C<LE<lt>manpage(section)E<gt>>", and Pod::Man will automatically format
those appropriately.  Both will render as I<manpage>(section).  The second
form, with LE<lt>E<gt>, is used to request that a POD formatter make a link
to the man page if possible.  As an exception, one normally omits the
section when referring to module documentation because not all systems
place it in section 3, although that is the default.  You may use
C<LE<lt>Module::NameE<gt>> for module references instead, but this is
optional because the translators are supposed to recognize module
references in pod, just as they do variable references like $foo and such.

References to other programs or functions are normally in the form of man
page references so that cross-referencing tools can provide the user with
links and the like.  It's possible to overdo this, though, so be careful not
to clutter your documentation with too much markup.  References to other
programs that are not given as man page references should be enclosed in
italics via IE<lt>E<gt>.

Major headers should be set out using a C<=head1> directive, and are
historically written in the rather startling ALL UPPER CASE format; this is
not mandatory, but it's strongly recommended so that sections have
consistent naming across different software packages.  The translators are
supposed to translate all caps into small caps.  Minor headers may be
included using C<=head2>, and are typically in mixed case.

The standard sections of a manual page are:

=over 4

=item NAME

Mandatory section; should be a comma-separated list of programs or
functions documented by this POD page, such as:

    foo, bar - programs to do something

Manual page indexers are often extremely picky about the format of this
section, so don't put anything in it except this line.  Every program or
function documented by this POD page should be listed, separated by a
comma and a space.  For a Perl module, just give the module name.  A
single dash, and only a single dash, should separate the list of programs
or functions from the description.  Do not use any markup such as
CE<lt>E<gt> or IE<lt>E<gt> anywhere in this line.  Functions should not be
qualified with C<()> or the like.  The description should ideally fit on a
single line, even if a man program replaces the dash with a few tabs.

=item SYNOPSIS

A short usage summary for programs and functions.  This section is
mandatory for section 3 pages.  For Perl module documentation, it's
usually convenient to have the contents of this section be a verbatim
block showing some (brief) examples of typical ways the module is used.

=item DESCRIPTION

Extended description and discussion of the program or functions, or the
body of the documentation for man pages that document something else.  If
particularly long, it's a good idea to break this up into subsections
C<=head2> directives like:

    =head2 Normal Usage

    =head2 Advanced Features

    =head2 Writing Configuration Files

or whatever is appropriate for your documentation.

For a module, this is generally where the documentation of the interfaces
provided by the module goes, usually in the form of a list with an
C<=item> for each interface.  Depending on how many interfaces there are,
you may want to put that documentation in separate METHODS, FUNCTIONS,
CLASS METHODS, or INSTANCE METHODS sections instead and save the
DESCRIPTION section for an overview.

=item OPTIONS

Detailed description of each of the command-line options taken by the
program.  This should be separate from the description for the use of
parsers like L<Pod::Usage>.  This is normally presented as a list, with
each option as a separate C<=item>.  The specific option string should be
enclosed in BE<lt>E<gt>.  Any values that the option takes should be
enclosed in IE<lt>E<gt>.  For example, the section for the option
B<--section>=I<manext> would be introduced with:

    =item B<--section>=I<manext>

Synonymous options (like both the short and long forms) are separated by a
comma and a space on the same C<=item> line, or optionally listed as their
own item with a reference to the canonical name.  For example, since
B<--section> can also be written as B<-s>, the above would be:

    =item B<-s> I<manext>, B<--section>=I<manext>

Writing the short option first is recommended because it's easier to read.
The long option is long enough to draw the eye to it anyway and the short
option can otherwise get lost in visual noise.

=item RETURN VALUE

What the program or function returns, if successful.  This section can be
omitted for programs whose precise exit codes aren't important, provided
they return 0 on success and non-zero on failure as is standard.  It
should always be present for functions.  For modules, it may be useful to
summarize return values from the module interface here, or it may be more
useful to discuss return values separately in the documentation of each
function or method the module provides.

=item ERRORS

Exceptions, error return codes, exit statuses, and errno settings.
Typically used for function or module documentation; program documentation
uses DIAGNOSTICS instead.  The general rule of thumb is that errors
printed to C<STDOUT> or C<STDERR> and intended for the end user are
documented in DIAGNOSTICS while errors passed internal to the calling
program and intended for other programmers are documented in ERRORS.  When
documenting a function that sets errno, a full list of the possible errno
values should be given here.

=item DIAGNOSTICS

All possible messages the program can print out and what they mean.  You
may wish to follow the same documentation style as the Perl documentation;
see perldiag(1) for more details (and look at the POD source as well).

If applicable, please include details on what the user should do to
correct the error; documenting an error as indicating "the input buffer is
too small" without telling the user how to increase the size of the input
buffer (or at least telling them that it isn't possible) aren't very
useful.

=item EXAMPLES

Give some example uses of the program or function.  Don't skimp; users
often find this the most useful part of the documentation.  The examples
are generally given as verbatim paragraphs.

Don't just present an example without explaining what it does.  Adding a
short paragraph saying what the example will do can increase the value of
the example immensely.

=item ENVIRONMENT

Environment variables that the program cares about, normally presented as
a list using C<=over>, C<=item>, and C<=back>.  For example:

    =over 6

    =item HOME

    Used to determine the user's home directory.  F<.foorc> in this
    directory is read for configuration details, if it exists.

    =back

Since environment variables are normally in all uppercase, no additional
special formatting is generally needed; they're glaring enough as it is.

=item FILES

All files used by the program or function, normally presented as a list,
and what it uses them for.  File names should be enclosed in FE<lt>E<gt>.
It's particularly important to document files that will be potentially
modified.

=item CAVEATS

Things to take special care with, sometimes called WARNINGS.

=item BUGS

Things that are broken or just don't work quite right.

=item RESTRICTIONS

Bugs you don't plan to fix.  :-)

=item NOTES

Miscellaneous commentary.

=item AUTHOR

Who wrote it (use AUTHORS for multiple people).  It's a good idea to
include your current email address (or some email address to which bug
reports should be sent) or some other contact information so that users
have a way of contacting you.  Remember that program documentation tends
to roam the wild for far longer than you expect and pick a contact method
that's likely to last.

=item HISTORY

Programs derived from other sources sometimes have this.  Some people keep
a modification log here, but that usually gets long and is normally better
maintained in a separate file.

=item COPYRIGHT AND LICENSE

For copyright

    Copyright YEAR(s) YOUR NAME(s)

(No, (C) is not needed.  No, "all rights reserved" is not needed.)

For licensing the easiest way is to use the same licensing as Perl itself:

    This library is free software; you may redistribute it and/or modify
    it under the same terms as Perl itself.

This makes it easy for people to use your module with Perl.  Note that
this licensing example is neither an endorsement or a requirement, you are
of course free to choose any licensing.

=item SEE ALSO

Other man pages to check out, like man(1), man(7), makewhatis(8), or
catman(8).  Normally a simple list of man pages separated by commas, or a
paragraph giving the name of a reference work.  Man page references, if
they use the standard C<name(section)> form, don't have to be enclosed in
LE<lt>E<gt> (although it's recommended), but other things in this section
probably should be when appropriate.

If the package has a mailing list, include a URL or subscription
instructions here.

If the package has a web site, include a URL here.

=back

Documentation of object-oriented libraries or modules may want to use
CONSTRUCTORS and METHODS sections, or CLASS METHODS and INSTANCE METHODS
sections, for detailed documentation of the parts of the library and save
the DESCRIPTION section for an overview.  Large modules with a function
interface may want to use FUNCTIONS for similar reasons.  Some people use
OVERVIEW to summarize the description if it's quite long.

Section ordering varies, although NAME must always be the first section
(you'll break some man page systems otherwise), and NAME, SYNOPSIS,
DESCRIPTION, and OPTIONS generally always occur first and in that order if
present.  In general, SEE ALSO, AUTHOR, and similar material should be
left for last.  Some systems also move WARNINGS and NOTES to last.  The
order given above should be reasonable for most purposes.

Some systems use CONFORMING TO to note conformance to relevant standards
and MT-LEVEL to note safeness for use in threaded programs or signal
handlers.  These headings are primarily useful when documenting parts of a
C library.

Finally, as a general note, try not to use an excessive amount of markup.
As documented here and in L<Pod::Man>, you can safely leave Perl variables,
module names, function names, man page references, and the like unadorned
by markup, and the POD translators will figure it all out for you.  This
makes it much easier to later edit the documentation.  Note that many
existing translators will do the wrong thing with email addresses when
wrapped in LE<lt>E<gt>, so don't do that.

You can check whether your documentation looks right by running

    % pod2text -o something.pod | less

If you have I<groff> installed, you can get an even better look this way:

    % pod2man something.pod | groff -Tps -mandoc > something.ps

Now view the resulting Postscript file to see whether everything checks out.

=head1 SEE ALSO

For additional information that may be more accurate for your specific
system, see either L<man(5)> or L<man(7)> depending on your system manual
section numbering conventions.

This documentation is maintained as part of the podlators distribution.
The current version is always available from its web site at
<http://www.eyrie.org/~eagle/software/podlators/>.

=head1 AUTHOR

Russ Allbery <rra@stanford.edu>, with large portions of this documentation
taken from the documentation of the original B<pod2man> implementation by
Larry Wall and Tom Christiansen.

=head1 COPYRIGHT AND LICENSE

Copyright 1999, 2000, 2001, 2004, 2006, 2008, 2010 Russ Allbery
<rra@stanford.edu>.

This documentation is free software; you may redistribute it and/or modify
it under the same terms as Perl itself.

=cut