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1 | =head1 NAME |
2 | |
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3 | perlpod - plain old documentation |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | A pod-to-whatever translator reads a pod file paragraph by paragraph, |
8 | and translates it to the appropriate output format. There are |
9 | three kinds of paragraphs: |
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10 | L<verbatim|/"Verbatim Paragraph">, |
11 | L<command|/"Command Paragraph">, and |
12 | L<ordinary text|/"Ordinary Block of Text">. |
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13 | |
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14 | =head2 Verbatim Paragraph |
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15 | |
16 | A verbatim paragraph, distinguished by being indented (that is, |
17 | it starts with space or tab). It should be reproduced exactly, |
18 | with tabs assumed to be on 8-column boundaries. There are no |
19 | special formatting escapes, so you can't italicize or anything |
20 | like that. A \ means \, and nothing else. |
21 | |
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22 | =head2 Command Paragraph |
23 | |
24 | All command paragraphs start with "=", followed by an |
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25 | identifier, followed by arbitrary text that the command can |
26 | use however it pleases. Currently recognized commands are |
27 | |
28 | =head1 heading |
29 | =head2 heading |
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30 | =head3 heading |
31 | =head4 heading |
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32 | =item text |
33 | =over N |
34 | =back |
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35 | =cut |
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36 | =pod |
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37 | =for X |
38 | =begin X |
39 | =end X |
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40 | |
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41 | =over 4 |
42 | |
43 | =item =pod |
44 | |
45 | =item =cut |
46 | |
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47 | The "=pod" directive does nothing beyond telling the compiler to lay |
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48 | off parsing code through the next "=cut". It's useful for adding |
49 | another paragraph to the doc if you're mixing up code and pod a lot. |
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50 | |
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51 | =item =head1 |
52 | |
53 | =item =head2 |
54 | |
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55 | =item =head3 |
56 | |
57 | =item =head4 |
58 | |
59 | Head1, head2, head3 and head4 produce first, second, third and fourth |
60 | level headings, with the text in the same paragraph as the "=headn" |
61 | directive forming the heading description. |
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62 | |
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63 | =item =over |
64 | |
65 | =item =back |
66 | |
67 | =item =item |
68 | |
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69 | Item, over, and back require a little more explanation: "=over" starts a |
70 | section specifically for the generation of a list using "=item" commands. At |
71 | the end of your list, use "=back" to end it. You will probably want to give |
72 | "4" as the number to "=over", as some formatters will use this for indentation. |
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73 | This should probably be a default. Note also that there are some basic rules |
74 | to using =item: don't use them outside of an =over/=back block, use at least |
75 | one inside an =over/=back block, you don't _have_ to include the =back if |
76 | the list just runs off the document, and perhaps most importantly, keep the |
77 | items consistent: either use "=item *" for all of them, to produce bullets, |
78 | or use "=item 1.", "=item 2.", etc., to produce numbered lists, or use |
79 | "=item foo", "=item bar", etc., i.e., things that looks nothing like bullets |
80 | or numbers. If you start with bullets or numbers, stick with them, as many |
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81 | formatters use the first "=item" type to decide how to format the list. |
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82 | |
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83 | =item =for |
84 | |
85 | =item =begin |
86 | |
87 | =item =end |
88 | |
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89 | For, begin, and end let you include sections that are not interpreted |
90 | as pod text, but passed directly to particular formatters. A formatter |
91 | that can utilize that format will use the section, otherwise it will be |
92 | completely ignored. The directive "=for" specifies that the entire next |
93 | paragraph is in the format indicated by the first word after |
94 | "=for", like this: |
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95 | |
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96 | =for html <br> |
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97 | <p> This is a raw HTML paragraph </p> |
98 | |
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99 | The paired commands "=begin" and "=end" work very similarly to "=for", but |
100 | instead of only accepting a single paragraph, all text from "=begin" to a |
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101 | paragraph with a matching "=end" are treated as a particular format. |
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102 | |
103 | Here are some examples of how to use these: |
104 | |
105 | =begin html |
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106 | |
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107 | <br>Figure 1.<IMG SRC="figure1.png"><br> |
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108 | |
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109 | =end html |
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110 | |
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111 | =begin text |
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112 | |
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113 | --------------- |
114 | | foo | |
115 | | bar | |
116 | --------------- |
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117 | |
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118 | ^^^^ Figure 1. ^^^^ |
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119 | |
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120 | =end text |
121 | |
122 | Some format names that formatters currently are known to accept include |
123 | "roff", "man", "latex", "tex", "text", and "html". (Some formatters will |
124 | treat some of these as synonyms.) |
125 | |
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126 | And don't forget, when using any command, that the command lasts up until |
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127 | the end of the B<paragraph>, not the line. Hence in the examples below, you |
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128 | can see the empty lines after each command to end its paragraph. |
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129 | |
130 | Some examples of lists include: |
131 | |
132 | =over 4 |
133 | |
134 | =item * |
135 | |
136 | First item |
137 | |
138 | =item * |
139 | |
140 | Second item |
141 | |
142 | =back |
143 | |
144 | =over 4 |
145 | |
146 | =item Foo() |
147 | |
148 | Description of Foo function |
149 | |
150 | =item Bar() |
151 | |
152 | Description of Bar function |
153 | |
154 | =back |
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155 | |
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156 | =back |
157 | |
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158 | =head2 Ordinary Block of Text |
159 | |
160 | It will be filled, and maybe even |
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161 | justified. Certain interior sequences are recognized both |
162 | here and in commands: |
163 | |
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164 | I<text> Italicize text, used for emphasis or variables |
165 | B<text> Embolden text, used for switches and programs |
166 | S<text> Text contains non-breaking spaces |
167 | C<code> Render code in a typewriter font, or give some other |
168 | indication that this represents program text |
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169 | L<name> A link (cross reference) to name |
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170 | L<name> manual page |
171 | L<name/ident> item in manual page |
172 | L<name/"sec"> section in other manual page |
173 | L<"sec"> section in this manual page |
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174 | (the quotes are optional) |
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175 | L</"sec"> ditto |
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176 | same as above but only 'text' is used for output. |
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177 | (Text can not contain the characters '/' and '|', |
178 | and should contain matched '<' or '>') |
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179 | L<text|name> |
180 | L<text|name/ident> |
181 | L<text|name/"sec"> |
182 | L<text|"sec"> |
183 | L<text|/"sec"> |
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184 | |
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185 | F<file> Used for filenames |
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186 | X<index> An index entry |
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187 | Z<> A zero-width character |
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188 | E<escape> A named character (very similar to HTML escapes) |
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189 | E<lt> A literal < |
190 | E<gt> A literal > |
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191 | E<sol> A literal / |
192 | E<verbar> A literal | |
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193 | (these are optional except in other interior |
194 | sequences and when preceded by a capital letter) |
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195 | E<n> Character number n (probably in ASCII) |
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196 | E<html> Some non-numeric HTML entity, such |
197 | as E<Agrave> |
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198 | |
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199 | Most of the time, you will only need a single set of angle brackets to |
200 | delimit the beginning and end of interior sequences. However, sometimes |
201 | you will want to put a right angle bracket (or greater-than sign '>') |
202 | inside of a sequence. This is particularly common when using a sequence |
203 | to provide a different font-type for a snippet of code. As with all |
204 | things in Perl, there is more than one way to do it. One way is to |
205 | simply escape the closing bracket using an C<E> sequence: |
206 | |
207 | C<$a E<lt>=E<gt> $b> |
208 | |
209 | This will produce: "C<$a E<lt>=E<gt> $b>" |
210 | |
211 | A more readable, and perhaps more "plain" way is to use an alternate set of |
212 | delimiters that doesn't require a ">" to be escaped. As of perl5.5.660, |
213 | doubled angle brackets ("<<" and ">>") may be used I<if and only if there |
214 | is whitespace immediately following the opening delimiter and immediately |
215 | preceding the closing delimiter!> For example, the following will do the |
216 | trick: |
217 | |
218 | C<< $a <=> $b >> |
219 | |
220 | In fact, you can use as many repeated angle-brackets as you like so |
221 | long as you have the same number of them in the opening and closing |
222 | delimiters, and make sure that whitespace immediately follows the last |
223 | '<' of the opening delimiter, and immediately precedes the first '>' of |
224 | the closing delimiter. So the following will also work: |
225 | |
226 | C<<< $a <=> $b >>> |
227 | C<<<< $a <=> $b >>>> |
228 | |
229 | This is currently supported by pod2text (Pod::Text), pod2man (Pod::Man), |
230 | and any other pod2xxx and Pod::Xxxx translator that uses Pod::Parser |
231 | 1.093 or later. |
232 | |
233 | |
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234 | =head2 The Intent |
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235 | |
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236 | That's it. The intent is simplicity, not power. I wanted paragraphs |
237 | to look like paragraphs (block format), so that they stand out |
238 | visually, and so that I could run them through fmt easily to reformat |
239 | them (that's F7 in my version of B<vi>). I wanted the translator (and not |
240 | me) to worry about whether " or ' is a left quote or a right quote |
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241 | within filled text, and I wanted it to leave the quotes alone, dammit, in |
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242 | verbatim mode, so I could slurp in a working program, shift it over 4 |
243 | spaces, and have it print out, er, verbatim. And presumably in a |
244 | constant width font. |
245 | |
246 | In particular, you can leave things like this verbatim in your text: |
247 | |
248 | Perl |
249 | FILEHANDLE |
250 | $variable |
251 | function() |
252 | manpage(3r) |
253 | |
254 | Doubtless a few other commands or sequences will need to be added along |
255 | the way, but I've gotten along surprisingly well with just these. |
256 | |
257 | Note that I'm not at all claiming this to be sufficient for producing a |
258 | book. I'm just trying to make an idiot-proof common source for nroff, |
259 | TeX, and other markup languages, as used for online documentation. |
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260 | Translators exist for B<pod2man> (that's for nroff(1) and troff(1)), |
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261 | B<pod2text>, B<pod2html>, B<pod2latex>, and B<pod2fm>. |
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262 | |
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263 | =head2 Embedding Pods in Perl Modules |
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264 | |
265 | You can embed pod documentation in your Perl scripts. Start your |
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266 | documentation with a "=head1" command at the beginning, and end it |
267 | with a "=cut" command. Perl will ignore the pod text. See any of the |
268 | supplied library modules for examples. If you're going to put your |
269 | pods at the end of the file, and you're using an __END__ or __DATA__ |
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270 | cut mark, make sure to put an empty line there before the first pod |
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271 | directive. |
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272 | |
273 | __END__ |
274 | |
275 | =head1 NAME |
276 | |
277 | modern - I am a modern module |
278 | |
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279 | If you had not had that empty line there, then the translators wouldn't |
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280 | have seen it. |
281 | |
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282 | =head2 Common Pod Pitfalls |
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283 | |
284 | =over 4 |
285 | |
286 | =item * |
287 | |
288 | Pod translators usually will require paragraphs to be separated by |
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289 | completely empty lines. If you have an apparently empty line with |
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290 | some spaces on it, this can cause odd formatting. |
291 | |
292 | =item * |
293 | |
294 | Translators will mostly add wording around a LE<lt>E<gt> link, so that |
295 | C<LE<lt>foo(1)E<gt>> becomes "the I<foo>(1) manpage", for example (see |
296 | B<pod2man> for details). Thus, you shouldn't write things like C<the |
297 | LE<lt>fooE<gt> manpage>, if you want the translated document to read |
298 | sensibly. |
299 | |
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300 | If you need total control of the text used for a link in the output |
301 | use the form LE<lt>show this text|fooE<gt> instead. |
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302 | |
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303 | =item * |
304 | |
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305 | The B<podchecker> command is provided to check pod syntax |
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306 | for errors and warnings. For example, it checks for completely |
307 | blank lines in pod segments and for unknown escape sequences. |
308 | It is still advised to pass it through |
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309 | one or more translators and proofread the result, or print out the |
310 | result and proofread that. Some of the problems found may be bugs in |
311 | the translators, which you may or may not wish to work around. |
312 | |
313 | =back |
314 | |
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315 | =head1 SEE ALSO |
316 | |
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317 | L<pod2man>, L<perlsyn/"PODs: Embedded Documentation">, |
318 | L<podchecker> |
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319 | |
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320 | =head1 AUTHOR |
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321 | |
322 | Larry Wall |
323 | |