X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlpod.pod;h=80c9ba134aa81205466973d35b57bc9cf55f526d;hb=aa92477d39232c1f4aabd6cccf539401dbada72b;hp=0997c71738a5baaeb98409f6621df827100998ba;hpb=5455df32d1cbb1b01b3af0f9b4f432fefbd8efb7;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlpod.pod b/pod/perlpod.pod index 0997c71..80c9ba1 100644 --- a/pod/perlpod.pod +++ b/pod/perlpod.pod @@ -1,315 +1,685 @@ + +=for comment +This document is in Pod format. To read this, use a Pod formatter, +like "perldoc perlpod". + =head1 NAME -perlpod - plain old documentation +perlpod - the Plain Old Documentation format =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: -L, -L, and -L. +Pod is a simple-to-use markup language used for writing documentation +for Perl, Perl programs, 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: +L, +L, and +L. + + +=head2 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 B, +I, C, L, and more. Such +codes are explained in the "L" +section, below. + =head2 Verbatim Paragraph -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. +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. + =head2 Command Paragraph -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 +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 - =head2 heading - =item text - =over N + =head1 Heading Text + =head2 Heading Text + =head3 Heading Text + =head4 Heading Text + =over indentlevel + =item stuff =back =cut =pod - =for X - =begin X - =end X + =begin format + =end format + =for format text... + +To explain them each in detail: + +=over + +=item C<=head1 I> + +=item C<=head2 I> + +=item C<=head3 I> + +=item C<=head4 I> + +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<$/> + +Such commands are explained in the +"L" section, below. -=over 4 +=item C<=over I> + +=item C<=item I> + +=item C<=back> + +Item, over, and back require a little more explanation: "=over" starts +a region specifically for the generation of a list using "=item" +commands, or for indenting (groups of) normal paragraphs. At the end +of your list, use "=back" to end it. The I option to +"=over" indicates how far over to indent, generally in ems (where +one em is the width of an "M" in the document's base font) or roughly +comparable units; if there is no I option, it defaults +to four. (And some formatters may just ignore whatever I +you provide.) In the I in C<=item I>, you may +use formatting codes, as seen here: + + =item Using C<$|> to Control Buffering + +Such commands are explained in the +"L" section, below. + +Note also that there are some basic rules to using "=over" ... +"=back" regions: + +=over + +=item * + +Don't use "=item"s outside of an "=over" ... "=back" region. + +=item * + +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. + +=item * + +Don't put "=headI" commands inside an "=over" ... "=back" region. + +=item * + +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. + +=back -=item =pod +=item C<=cut> -=item =cut +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" directive does nothing beyond telling the compiler to lay -off parsing code through the next "=cut". It's useful for adding -another paragraph to the doc if you're mixing up code and pod a lot. +=item C<=pod> -=item =head1 +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 I 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 =head2 + =item stuff() -Head1 and head2 produce first and second level headings, with the text in -the same paragraph as the "=headn" directive forming the heading description. + This function does stuff. -=item =over + =cut -=item =back + sub stuff { + ... + } -=item =item + =pod -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. + Remember to check its return value, as in: -=item =for + stuff() || die "Couldn't do stuff!"; -=item =begin + =cut -=item =end +=item C<=begin I> -For, begin, and end let you include sections that are not interpreted -as pod text, but passed directly to particular formatters. A formatter -that can utilize that format will use the section, otherwise it will be -completely ignored. The directive "=for" specifies that the entire next -paragraph is in the format indicated by the first word after -"=for", like this: +=item C<=end I> - =for html
+=item C<=for I I> + +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, otherwise it +will be completely ignored. + +A command "=begin I", some paragraphs, and a +command "=end I", mean that the text/data inbetween +is meant for formatters that understand the special format +called I. For example, + + =begin html + +

This is a raw HTML paragraph

-The paired commands "=begin" and "=end" work very similarly to "=for", but -instead of only accepting a single paragraph, all text from "=begin" to a -paragraph with a matching "=end" are treated as a particular format. + =end html + +The command "=for I I" +specifies that the remainder of just this paragraph (starting +right after I) is in that special format. + + =for html
+

This is a raw HTML paragraph

+ +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 + =begin html + +
Figure 1.

+ + =end html -
Figure 1.
+ =begin text - =end html + --------------- + | foo | + | bar | + --------------- - =begin text + ^^^^ Figure 1. ^^^^ - --------------- - | foo | - | bar | - --------------- + =end text - ^^^^ Figure 1. ^^^^ +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 synonyms.) - =end text +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: -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 synonyms.) + =for comment + Make sure that all the available options are documented! -And don't forget, when using any command, that the command lasts up until -the end of the B, not the line. Hence in the examples below, you -can see the empty lines after each command to end its paragraph. +Some I will require a leading colon (as in +C<"=for :formatname">, or +C<"=begin :formatname" ... "=end :formatname">), +to signal that the text is not raw data, but instead I 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 formatting as a footnote). + +=back + +And don't forget, when using any command, that the command lasts up +until the end of its I, 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: - =over 4 + =over + + =item * + + First item + + =item * + + Second item + + =back + + =over + + =item Foo() + + Description of Foo function - =item * + =item Bar() - First item + Description of Bar function - =item * + =back - Second item - =back +=head2 Formatting Codes - =over 4 +In ordinary paragraphs and in some command paragraphs, various +formatting codes (a.k.a. "interior sequences") can be used: - =item Foo() +=for comment + "interior sequences" is such an opaque term. + Prefer "formatting codes" instead. - Description of Foo function +=over - =item Bar() +=item CtextE> -- italic text - Description of Bar function +Used for emphasis ("Ccareful!E>") and parameters +("CLABELE>") - =back +=item CtextE> -- bold text + +Used for switches ("C-nE switch>"), programs +("CchfnE for that>"), +emphasis ("Ccareful!E>"), and so on +("CautovivificationE>"). + +=item CcodeE> -- code text + +Renders code in a typewriter font, or gives some other indication that +this represents program text ("Cgmtime($^T)E>") or some other +form of computerese ("Cdrwxr-xr-xE>"). + +=item CnameE> -- a hyperlink + +There are various syntaxes, listed below. In the syntaxes given, +C, C, and C
cannot contain the characters +'/' and '|'; and any '<' or '>' should be matched. + +=over + +=item * + +CnameE> + +Link to a Perl manual page (e.g., CNet::PingE>). Note +that C should not contain spaces. This syntax +is also occasionally used for references to UNIX man pages, as in +Ccrontab(5)E>. + +=item * + +Cname/"sec"E> or Cname/secE> + +Link to a section in other manual page. E.g., +Cperlsyn/"For Loops"E> + +=item * + +C/"sec"E> or C/secE> or C"sec"E> + +Link to a section in this manual page. E.g., +C/"Object Methods"E> =back -=head2 Ordinary Block of Text - -It will be filled, and maybe even -justified. Certain interior sequences are recognized both -here and in commands: - - I italicize text, used for emphasis or variables - B embolden text, used for switches and programs - S text contains non-breaking spaces - C literal code - L A link (cross reference) to name - L manual page - L item in manual page - L section in other manual page - L<"sec"> section in this manual page - (the quotes are optional) - L ditto - same as above but only 'text' is used for output. - (Text can not contain the characters '/' and '|', - and should contain matched '<' or '>') - L - L - L - L - L - - F Used for filenames - X An index entry - Z<> A zero-width character - E A named character (very similar to HTML escapes) - E A literal < - E A literal > - E A literal / - E A literal | - (these are optional except in other interior - sequences and when preceded by a capital letter) - E Character number n (probably in ASCII) - E Some non-numeric HTML entity, such - as E - -Most of the time, you will only need a single set of angle brackets to -delimit the beginning and end of interior sequences. However, sometimes -you will want to put a right angle bracket (or greater-than sign '>') -inside of a sequence. This is particularly common when using a sequence -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 C sequence: +A section is started by the named heading or item. For +example, Cperlvar/$.E> or Cperlvar/"$."E> both +link to the section started by "C<=item $.>" in perlvar. And +Cperlsyn/For LoopsE> or Cperlsyn/"For Loops"E> +both link to the section started by "C<=head2 For Loops>" +in perlsyn. + +To control what text is used for display, you +use "Ctext|...E>", as in: + +=over + +=item * + +Ctext|nameE> + +Link this text to that manual page. E.g., +CPerl Error Messages|perldiagE> + +=item * + +Ctext|name/"sec"E> or Ctext|name/secE> + +Link this text to that section in that manual page. E.g., +CSWITCH statements|perlsyn/"Basic BLOCKs and Switch +Statements"E> + +=item * + +Ctext|/"sec"E> or Ctext|/secE> +or Ctext|"sec"E> + +Link this text to that section in this manual page. E.g., +Cthe various attributes|/"Member Data"E> + +=back + +Or you can link to a web page: + +=over + +=item * + +Cscheme:...E> + +Links to an absolute URL. For example, +Chttp://www.perl.org/E>. But note +that there is no corresponding Ctext|scheme:...E> syntax, for +various reasons. + +=back + +=item CescapeE> -- a character escape + +Very similar to HTML/XML C<&I;> "entity references": + +=over + +=item * + +CltE> -- a literal E (less than) + +=item * + +CgtE> -- a literal E (greater than) + +=item * + +CverbarE> -- a literal | (Itical I) + +=item * + +CsolE> = a literal / (Iidus) + +The above four are optional except in other formatting codes, +notably C...E>, and when preceded by a +capital letter. + +=item * + +ChtmlnameE> + +Some non-numeric HTML entity name, such as CeacuteE>, +meaning the same thing as C<é> in HTML -- i.e., a lowercase +e with an acute (/-shaped) accent. + +=item * + +CnumberE> + +The ASCII/Latin-1/Unicode character with that number. A +leading "0x" means that I is hex, as in +C0x201EE>. A leading "0" means that I is octal, +as in C075E>. Otherwise I is interpreted as being +in decimal, as in C181E>. + +Note that older Pod formatters might not recognize octal or +hex numeric escapes, and that many formatters cannot reliably +render characters above 255. (Some formatters may even have +to use compromised renderings of Latin-1 characters, like +rendering CeacuteE> as just a plain "e".) + +=back + +=item CfilenameE> -- used for filenames + +Typically displayed in italics. Example: "C.cshrcE>" + +=item CtextE> -- text contains non-breaking spaces + +This means that the words in I should not be broken +across lines. Example: S$x ? $y : $zE>>. + +=item Ctopic nameE> -- an index entry + +This is ignored by most formatters, but some may use it for building +indexes. It always renders as empty-string. +Example: Cabsolutizing relative URLsE> + +=item CE> -- a null (zero-effect) formatting code + +This is rarely used. It's one way to get around using an +EE...E code sometimes. For example, instead of +"CltE3>" (for "NE3") you could write +"CEE3>" (the "ZEE" breaks up the "N" and +the "E" so they can't be considered +the part of a (fictitious) "NE...E" code. + +=for comment + This was formerly explained as a "zero-width character". But it in + most parser models, it parses to nothing at all, as opposed to parsing + as if it were a E or E, which are REAL zero-width characters. + So "width" and "character" are exactly the wrong words. + +=back + +Most of the time, you will need only a single set of angle brackets to +delimit the beginning and end of formatting codes. However, +sometimes you will want to put a real right angle bracket (a +greater-than sign, '>') inside of a formatting code. This is particularly +common when using a formatting code to provide a different font-type for a +snippet of code. As with all things in Perl, there is more than +one way to do it. One way is to simply escape the closing bracket +using an C code: C<$a E=E $b> This will produce: "C<$a E=E $b>" -A more readable, and perhaps more "plain" way is to use an alternate set of -delimiters that doesn't require a ">" to be escaped. As of perl5.5.660, -doubled angle brackets ("<<" and ">>") may be used I For example, the following will do the -trick: +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 standard starting with perl5.5.660, doubled +angle brackets ("<<" and ">>") may be used I 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. So the following will also work: +'<' 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 >>>> + C<<<< $a <=> $b >>>> -This is currently supported by pod2text (Pod::Text), pod2man (Pod::Man), -and any other pod2xxx and Pod::Xxxx translator that uses Pod::Parser -1.093 or later. +And they all mean exactly the same as this: + + C<$a E=E $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 $! + $foo->bar(); + +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: + + CEthing.dat") || die $!> + C<$foo-Ebar(); >> + +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 later. =head2 The Intent -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). 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 (that's for nroff(1) and troff(1)), -B, B, B, and B. +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 C easily to reformat +them (that's F7 in my version of B, or Esc Q in my version of +B). I wanted the translator to always leave the C<'> and C<`> and +C<"> 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 B, B, +B (that's for nroff(1) and troff(1)), B, and +B. Various others are available in CPAN. + =head2 Embedding Pods in Perl Modules -You can embed pod documentation in your Perl scripts. Start your -documentation with a "=head1" command at the beginning, and end it -with a "=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 an empty line there before the first pod -directive. +You can embed Pod documentation in your Perl modules and scripts. +Start your documentation 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. + + __END__ - __END__ + =head1 NAME - =head1 NAME + Time::Local - efficiently compute time from local and GMT time - modern - I am a modern module +Without that empty line before the "=head1", many translators wouldn't +have recognized the "=head1" as starting a Pod block. -If you had not had that empty line there, then the translators wouldn't -have seen it. +=head2 Hints for Writing Pod -=head2 Common Pod Pitfalls +=over + +=item * + +The B 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 commands 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. + +=item * -=over 4 +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 L module, +(available in CPAN), and looking at the resulting code. The experimental +L module in CPAN might also be useful. =item * -Pod translators usually will require paragraphs to be separated by -completely empty lines. If you have an apparently empty line with -some spaces on it, this can cause odd formatting. +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. + =cut + 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. + + =cut + + sub boom { + ... =item * -Translators will mostly add wording around a LEE link, so that -Cfoo(1)E> becomes "the I(1) manpage", for example (see -B for details). Thus, you shouldn't write things like CfooE manpage>, if you want the translated document to read -sensibly. +Some older Pod translators require paragraphs (including command +paragraphs like "=head2 Functions") to be separated by I +empty lines. If you have an apparently empty line with some spaces +on it, this might not count as a separator for those translators, and +that could cause odd formatting. + +=item * -If you don need or want total control of the text used for a -link in the output use the form LEshow this text|fooE -instead. +Older translators might add wording around an LEE link, so that +CFoo::BarE> may become "the Foo::Bar manpage", for example. +So you shouldn't write things like CfooE +documentation>, if you want the translated document to read sensibly +-- instead write CFoo::Bar|Foo::BarE documentation> or +Cthe Foo::Bar documentation|Foo::BarE>, to control how the +link comes out. =item * -The script F in the Perl source distribution -provides skeletal checking for lines that look empty but aren't -B, 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. +Going past the 70th column in a verbatim block might be ungracefully +wrapped by some formatters. =back =head1 SEE ALSO -L and L +L, L, +L, L, L, L, L. =head1 AUTHOR -Larry Wall +Larry Wall, Sean M. Burke +=cut