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PERLPOD(1)			 Perl Programmers Reference Guide		       PERLPOD(1)

       perlpod - the Plain Old Documentation format

       Pod is a simple-to-use markup language used for writing documentation for Perl, Perl pro-
       grams, and Perl modules.

       Translators are available for converting Pod to various formats like plain text, HTML, man
       pages, and more.

       Pod markup consists of three basic kinds of paragraphs: ordinary, verbatim, and command.

       Ordinary Paragraph

       Most paragraphs in your documentation will be ordinary blocks of text, like this one.  You
       can simply type in your text without any markup whatsoever, and with just a blank line
       before and after.  When it gets formatted, it will undergo minimal formatting, like being
       rewrapped, probably put into a proportionally spaced font, and maybe even justified.

       You can use formatting codes in ordinary paragraphs, for bold, italic, "code-style",
       hyperlinks, and more.  Such codes are explained in the "Formatting Codes" section, below.

       Verbatim Paragraph

       Verbatim paragraphs are usually used for presenting a codeblock or other text which does
       not require any special parsing or formatting, and which shouldn't be wrapped.

       A verbatim paragraph is distinguished by having its first character be a space or a tab.
       (And commonly, all its lines begin with spaces and/or tabs.)  It should be reproduced
       exactly, with tabs assumed to be on 8-column boundaries.  There are no special formatting
       codes, so you can't italicize or anything like that.  A \ means \, and nothing else.

       Command Paragraph

       A command paragraph is used for special treatment of whole chunks of text, usually as
       headings or parts of lists.

       All command paragraphs (which are typically only one line long) start with "=", followed
       by an identifier, followed by arbitrary text that the command can use however it pleases.
       Currently recognized commands are

	   =head1 Heading Text
	   =head2 Heading Text
	   =head3 Heading Text
	   =head4 Heading Text
	   =over indentlevel
	   =item stuff
	   =begin format
	   =end format
	   =for format text...

       To explain them each in detail:

       "=head1 Heading Text"
       "=head2 Heading Text"
       "=head3 Heading Text"
       "=head4 Heading Text"
	   Head1 through head4 produce headings, head1 being the highest level.  The text in the
	   rest of this paragraph is the content of the heading.  For example:

	     =head2 Object Attributes

	   The text "Object Attributes" comprises the heading there.  (Note that head3 and head4
	   are recent additions, not supported in older Pod translators.)  The text in these
	   heading commands can use formatting codes, as seen here:

	     =head2 Possible Values for C<$/>

	   Such commands are explained in the "Formatting Codes" section, below.

       "=over indentlevel"
       "=item stuff..."
	   Item, over, and back require a little more explanation:  "=over" starts a region
	   specifically for the generation of a list using "=item" commands, or for indenting
	   (groups of) normal paragraphs.  At the end of your list, use "=back" to end it.  The
	   indentlevel option to "=over" indicates how far over to indent, generally in ems
	   (where one em is the width of an "M" in the document's base font) or roughly compara-
	   ble units; if there is no indentlevel option, it defaults to four.  (And some format-
	   ters may just ignore whatever indentlevel you provide.)  In the stuff in "=item
	   stuff...", you may use formatting codes, as seen here:

	     =item Using C<$|> to Control Buffering

	   Such commands are explained in the "Formatting Codes" section, below.

	   Note also that there are some basic rules to using "=over" ...  "=back" regions:

	   o   Don't use "=item"s outside of an "=over" ... "=back" region.

	   o   The first thing after the "=over" command should be an "=item", unless there
	       aren't going to be any items at all in this "=over" ... "=back" region.

	   o   Don't put "=headn" commands inside an "=over" ... "=back" region.

	   o   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. -- namely, things that look
	       nothing like bullets or numbers.

	       If you start with bullets or numbers, stick with them, as formatters use the first
	       "=item" type to decide how to format the list.

	   To end a Pod block, use a blank line, then a line beginning with "=cut", and a blank
	   line after it.  This lets Perl (and the Pod formatter) know that this is where Perl
	   code is resuming.  (The blank line before the "=cut" is not technically necessary, but
	   many older Pod processors require it.)

	   The "=pod" command by itself doesn't do much of anything, but it signals to Perl (and
	   Pod formatters) that a Pod block starts here.  A Pod block starts with any command
	   paragraph, so a "=pod" command is usually used just when you want to start a Pod block
	   with an ordinary paragraph or a verbatim paragraph.	For example:

	     =item stuff()

	     This function does stuff.


	     sub stuff {


	     Remember to check its return value, as in:

	       stuff() || die "Couldn't do stuff!";


       "=begin formatname"
       "=end formatname"
       "=for formatname text..."
	   For, begin, and end will let you have regions of text/code/data that are not generally
	   interpreted as normal Pod text, but are passed directly to particular formatters, or
	   are otherwise special.  A formatter that can use that format will use the region, oth-
	   erwise it will be completely ignored.

	   A command "=begin formatname", some paragraphs, and a command "=end formatname", mean
	   that the text/data inbetween is meant for formatters that understand the special for-
	   mat called formatname.  For example,

	     =begin html

	     <hr> <img src="thang.png">
	     <p> This is a raw HTML paragraph </p>

	     =end html

	   The command "=for formatname text..."  specifies that the remainder of just this para-
	   graph (starting right after formatname) is in that special format.

	     =for html <hr> <img src="thang.png">
	     <p> This is a raw HTML paragraph </p>

	   This means the same thing as the above "=begin html" ... "=end html" region.

	   That is, with "=for", you can have only one paragraph's worth of text (i.e., the text
	   in "=foo targetname text..."), but with "=begin targetname" ... "=end targetname", you
	   can have any amount of stuff inbetween.  (Note that there still must be a blank line
	   after the "=begin" command and a blank line before the "=end" command.

	   Here are some examples of how to use these:

	     =begin html

	     <br>Figure 1.<br><IMG SRC="figure1.png"><br>

	     =end html

	     =begin text

	       |  foo	     |
	       |	bar  |

	     ^^^^ Figure 1. ^^^^

	     =end text

	   Some format names that formatters currently are known to accept include "roff", "man",
	   "latex", "tex", "text", and "html".	(Some formatters will treat some of these as syn-

	   A format name of "comment" is common for just making notes (presumably to yourself)
	   that won't appear in any formatted version of the Pod document:

	     =for comment
	     Make sure that all the available options are documented!

	   Some formatnames will require a leading colon (as in "=for :formatname", or "=begin
	   :formatname" ... "=end :formatname"), to signal that the text is not raw data, but
	   instead is Pod text (i.e., possibly containing formatting codes) that's just not for
	   normal formatting (e.g., may not be a normal-use paragraph, but might be for format-
	   ting as a footnote).

       And don't forget, when using any command, that the command lasts up until the end of its
       paragraph, not its line.  So in the examples below, you can see that every command needs
       the blank line after it, to end its paragraph.

       Some examples of lists include:


	 =item *

	 First item

	 =item *

	 Second item



	 =item Foo()

	 Description of Foo function

	 =item Bar()

	 Description of Bar function


       Formatting Codes

       In ordinary paragraphs and in some command paragraphs, various formatting codes (a.k.a.
       "interior sequences") can be used:

       "I<text>" -- italic text
	   Used for emphasis (""be I<careful!>"") and parameters (""redo I<LABEL>"")

       "B<text>" -- bold text
	   Used for switches (""perl's B<-n> switch""), programs (""some systems provide a
	   B<chfn> for that""), emphasis (""be B<careful!>""), and so on (""and that feature is
	   known as B<autovivification>"").

       "C<code>" -- code text
	   Renders code in a typewriter font, or gives some other indication that this represents
	   program text (""C<gmtime($^T)>"") or some other form of computerese

       "L<name>" -- a hyperlink
	   There are various syntaxes, listed below.  In the syntaxes given, "text", "name", and
	   "section" cannot contain the characters '/' and '|'; and any '<' or '>' should be

	   o   "L<name>"

	       Link to a Perl manual page (e.g., "L<Net::Ping>").  Note that "name" should not
	       contain spaces.	This syntax is also occasionally used for references to UNIX man
	       pages, as in "L<crontab(5)>".

	   o   "L<name/"sec">" or "L<name/sec>"

	       Link to a section in other manual page.	E.g., "L<perlsyn/"For Loops">"

	   o   "L</"sec">" or "L</sec>" or "L<"sec">"

	       Link to a section in this manual page.  E.g., "L</"Object Methods">"

	   A section is started by the named heading or item.  For example, "L<perlvar/$.>" or
	   "L<perlvar/"$.">" both link to the section started by ""=item $."" in perlvar.  And
	   "L<perlsyn/For Loops>" or "L<perlsyn/"For Loops">" both link to the section started by
	   ""=head2 For Loops"" in perlsyn.

	   To control what text is used for display, you use ""L<text|...>"", as in:

	   o   "L<text|name>"

	       Link this text to that manual page.  E.g., "L<Perl Error Messages|perldiag>"

	   o   "L<text|name/"sec">" or "L<text|name/sec>"

	       Link this text to that section in that manual page.  E.g., "L<SWITCH state-
	       ments|perlsyn/"Basic BLOCKs and Switch Statements">"

	   o   "L<text|/"sec">" or "L<text|/sec>" or "L<text|"sec">"

	       Link this text to that section in this manual page.  E.g., "L<the various
	       attributes|/"Member Data">"

	   Or you can link to a web page:

	   o   "L<scheme:...>"

	       Links to an absolute URL.  For example, "L<http://www.perl.org/>".  But note that
	       there is no corresponding "L<text|scheme:...>" syntax, for various reasons.

       "E<escape>" -- a character escape
	   Very similar to HTML/XML "&foo;" "entity references":

	   o   "E<lt>" -- a literal < (less than)

	   o   "E<gt>" -- a literal > (greater than)

	   o   "E<verbar>" -- a literal | (vertical bar)

	   o   "E<sol>" = a literal / (solidus)

	       The above four are optional except in other formatting codes, notably "L<...>",
	       and when preceded by a capital letter.

	   o   "E<htmlname>"

	       Some non-numeric HTML entity name, such as "E<eacute>", meaning the same thing as
	       "&eacute;" in HTML -- i.e., a lowercase e with an acute (/-shaped) accent.

	   o   "E<number>"

	       The ASCII/Latin-1/Unicode character with that number.  A leading "0x" means that
	       number is hex, as in "E<0x201E>".  A leading "0" means that number is octal, as in
	       "E<075>".  Otherwise number is interpreted as being in decimal, as in "E<181>".

	       Note that older Pod formatters might not recognize octal or hex numeric escapes,
	       and that many formatters cannot reliably render characters above 255.  (Some for-
	       matters may even have to use compromised renderings of Latin-1 characters, like
	       rendering "E<eacute>" as just a plain "e".)

       "F<filename>" -- used for filenames
	   Typically displayed in italics.  Example: ""F<.cshrc>""

       "S<text>" -- text contains non-breaking spaces
	   This means that the words in text should not be broken across lines.  Example:
	   "S<$x ? $y : $z>".

       "X<topic name>" -- an index entry
	   This is ignored by most formatters, but some may use it for building indexes.  It
	   always renders as empty-string.  Example: "X<absolutizing relative URLs>"

       "Z<>" -- a null (zero-effect) formatting code
	   This is rarely used.  It's one way to get around using an E<...> code sometimes.  For
	   example, instead of ""NE<lt>3"" (for "N<3") you could write ""NZ<><3"" (the "Z<>"
	   breaks up the "N" and the "<" so they can't be considered the part of a (fictitious)
	   "N<...>" code.

       Most of the time, you will need only a single set of angle brackets to delimit the begin-
       ning and end of formatting codes.  However, sometimes you will want to put a real right
       angle bracket (a greater-than sign, '>') inside of a formatting code.  This is particu-
       larly common when using a formatting code to provide a different font-type for a snippet
       of code.  As with all things in Perl, there is more than one way to do it.  One way is to
       simply escape the closing bracket using an "E" code:

	   C<$a E<lt>=E<gt> $b>

       This will produce: ""$a <=> $b""

       A more readable, and perhaps more "plain" way is to use an alternate set of delimiters
       that doesn't require a single ">" to be escaped.  With the Pod formatters that are stan-
       dard starting with perl5.5.660, doubled angle brackets ("<<" and ">>") may be used if and
       only if there is whitespace right after the opening delimiter and whitespace right before
       the closing delimiter!  For example, the following will do the trick:

	   C<< $a <=> $b >>

       In fact, you can use as many repeated angle-brackets as you like so long as you have the
       same number of them in the opening and closing delimiters, and make sure that whitespace
       immediately follows the last '<' of the opening delimiter, and immediately precedes the
       first '>' of the closing delimiter.  (The whitespace is ignored.)  So the following will
       also work:

	   C<<< $a <=> $b >>>
	   C<<<<  $a <=> $b	>>>>

       And they all mean exactly the same as this:

	   C<$a E<lt>=E<gt> $b>

       As a further example, this means that if you wanted to put these bits of code in "C"
       (code) style:

	   open(X, ">>thing.dat") || die $!

       you could do it like so:

	   C<<< open(X, ">>thing.dat") || die $! >>>
	   C<< $foo->bar(); >>

       which is presumably easier to read than the old way:

	   C<open(X, "E<gt>E<gt>thing.dat") || die $!>
	   C<$foo-E<gt>bar(); >>

       This is currently supported by pod2text (Pod::Text), pod2man (Pod::Man), and any other
       pod2xxx or Pod::Xxxx translators that use Pod::Parser 1.093 or later, or Pod::Tree 1.02 or

       The Intent

       The intent is simplicity of use, not power of expression.  Paragraphs 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 vi, or Esc Q in my version of
       emacs).	I wanted the translator to always leave the "'" and "`" and """ quotes alone, in
       verbatim mode, so I could slurp in a working program, shift it over four spaces, and have
       it print out, er, verbatim.  And presumably in a monospace font.

       The Pod format is not necessarily sufficient for writing a book.  Pod is just meant to be
       an idiot-proof common source for nroff, HTML, TeX, and other markup languages, as used for
       online documentation.  Translators exist for pod2text, pod2html, pod2man (that's for
       nroff(1) and troff(1)), pod2latex, and pod2fm.  Various others are available in CPAN.

       Embedding Pods in Perl Modules

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


	 =head1 NAME

	 Time::Local - efficiently compute time from local and GMT time

       Without that empty line before the "=head1", many translators wouldn't have recognized the
       "=head1" as starting a Pod block.

       Hints for Writing Pod

       o   The podchecker command is provided for checking Pod syntax for errors and warnings.
	   For example, it checks for completely blank lines in Pod blocks and for unknown com-
	   mands and formatting codes.	You should still also pass your document 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.

       o   If you're more familiar with writing in HTML than with writing in Pod, you can try
	   your hand at writing documentation in simple HTML, and converting it to Pod with the
	   experimental Pod::HTML2Pod module, (available in CPAN), and looking at the resulting
	   code.  The experimental Pod::PXML module in CPAN might also be useful.

       o   Many older Pod translators require the lines before every Pod command and after every
	   Pod command (including "=cut"!) to be a blank line.	Having something like this:

	    # - - - - - - - - - - - -
	    =item $firecracker->boom()

	    This noisily detonates the firecracker object.
	    sub boom {

	   ...will make such Pod translators completely fail to see the Pod block at all.

	   Instead, have it like this:

	    # - - - - - - - - - - - -

	    =item $firecracker->boom()

	    This noisily detonates the firecracker object.


	    sub boom {

       o   Some older Pod translators require paragraphs (including command paragraphs like
	   "=head2 Functions") to be separated by completely empty lines.  If you have an appar-
	   ently empty line with some spaces on it, this might not count as a separator for those
	   translators, and that could cause odd formatting.

       o   Older translators might add wording around an L<> link, so that "L<Foo::Bar>" may
	   become "the Foo::Bar manpage", for example.	So you shouldn't write things like "the
	   L<foo> documentation", if you want the translated document to read sensibly -- instead
	   write "the L<Foo::Bar|Foo::Bar> documentation" or "L<the Foo::Bar documenta-
	   tion|Foo::Bar>", to control how the link comes out.

       o   Going past the 70th column in a verbatim block might be ungracefully wrapped by some

       perlpodspec, "PODs: Embedded Documentation" in perlsyn, perlnewmod, perldoc, pod2html,
       pod2man, podchecker.

       Larry Wall, Sean M. Burke

perl v5.8.0				    2003-02-18				       PERLPOD(1)
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