1Parser(3) User Contributed Perl Documentation Parser(3)
2
6 HTML::Parser - HTML parser class
7
9 use HTML::Parser ();
10 # Create parser object
12 $p = HTML::Parser->new( api_version => 3,
13 start_h => [\&start, "tagname, attr"],
14 end_h => [\&end, "tagname"],
15 marked_sections => 1,
16 );
17 # Parse document text chunk by chunk
19 $p->parse($chunk1);
20 $p->parse($chunk2);
21 #...
22 $p->eof; # signal end of document
23 # Parse directly from file
25 $p->parse_file("foo.html");
26 # or
27 open(my $fh, "<:utf8", "foo.html") || die;
28 $p->parse_file($fh);
29
31 Objects of the "HTML::Parser" class will recognize markup and separate
32 it from plain text (alias data content) in HTML documents. As
33 different kinds of markup and text are recognized, the corresponding
34 event handlers are invoked.
35 "HTML::Parser" is not a generic SGML parser. We have tried to make it
37 able to deal with the HTML that is actually "out there", and it
38 normally parses as closely as possible to the way the popular web
39 browsers do it instead of strictly following one of the many HTML
40 specifications from W3C. Where there is disagreement, there is often
41 an option that you can enable to get the official behaviour.
42 The document to be parsed may be supplied in arbitrary chunks. This
44 makes on-the-fly parsing as documents are received from the network
45 possible.
46 If event driven parsing does not feel right for your application, you
48 might want to use "HTML::PullParser". This is an "HTML::Parser"
49 subclass that allows a more conventional program structure.
50
52 The following method is used to construct a new "HTML::Parser" object:
53 $p = HTML::Parser->new( %options_and_handlers )
55 This class method creates a new "HTML::Parser" object and returns
56 it. Key/value argument pairs may be provided to assign event
57 handlers or initialize parser options. The handlers and parser
58 options can also be set or modified later by the method calls
59 described below.
60 If a top level key is in the form "<event>_h" (e.g., "text_h") then
62 it assigns a handler to that event, otherwise it initializes a
63 parser option. The event handler specification value must be an
64 array reference. Multiple handlers may also be assigned with the
65 'handlers => [%handlers]' option. See examples below.
66 If new() is called without any arguments, it will create a parser
68 that uses callback methods compatible with version 2 of
69 "HTML::Parser". See the section on "version 2 compatibility" below
70 for details.
71 The special constructor option 'api_version => 2' can be used to
73 initialize version 2 callbacks while still setting other options
74 and handlers. The 'api_version => 3' option can be used if you
75 don't want to set any options and don't want to fall back to v2
76 compatible mode.
77 Examples:
79 $p = HTML::Parser->new(api_version => 3,
81 text_h => [ sub {...}, "dtext" ]);
82 This creates a new parser object with a text event handler
84 subroutine that receives the original text with general entities
85 decoded.
86 $p = HTML::Parser->new(api_version => 3,
88 start_h => [ 'my_start', "self,tokens" ]);
89 This creates a new parser object with a start event handler method
91 that receives the $p and the tokens array.
92 $p = HTML::Parser->new(api_version => 3,
94 handlers => { text => [\@array, "event,text"],
95 comment => [\@array, "event,text"],
96 });
97 This creates a new parser object that stores the event type and the
99 original text in @array for text and comment events.
100 The following methods feed the HTML document to the "HTML::Parser"
102 object:
103 $p->parse( $string )
105 Parse $string as the next chunk of the HTML document. Handlers
106 invoked should not attempt to modify the $string in-place until
107 $p->parse returns.
108 If an invoked event handler aborts parsing by calling $p->eof, then
110 $p->parse() will return a FALSE value. Otherwise the return value
111 is a reference to the parser object ($p).
112 $p->parse( $code_ref )
114 If a code reference is passed as the argument to be parsed, then
115 the chunks to be parsed are obtained by invoking this function
116 repeatedly. Parsing continues until the function returns an empty
117 (or undefined) result. When this happens $p->eof is automatically
118 signaled.
119 Parsing will also abort if one of the event handlers calls $p->eof.
121 The effect of this is the same as:
123 while (1) {
125 my $chunk = &$code_ref();
126 if (!defined($chunk) || !length($chunk)) {
127 $p->eof;
128 return $p;
129 }
130 $p->parse($chunk) || return undef;
131 }
132 But it is more efficient as this loop runs internally in XS code.
134 $p->parse_file( $file )
136 Parse text directly from a file. The $file argument can be a
137 filename, an open file handle, or a reference to an open file
138 handle.
139 If $file contains a filename and the file can't be opened, then the
141 method returns an undefined value and $! tells why it failed.
142 Otherwise the return value is a reference to the parser object.
143 If a file handle is passed as the $file argument, then the file
145 will normally be read until EOF, but not closed.
146 If an invoked event handler aborts parsing by calling $p->eof, then
148 $p->parse_file() may not have read the entire file.
149 On systems with multi-byte line terminators, the values passed for
151 the offset and length argspecs may be too low if parse_file() is
152 called on a file handle that is not in binary mode.
153 If a filename is passed in, then parse_file() will open the file in
155 binary mode.
156 $p->eof
158 Signals the end of the HTML document. Calling the $p->eof method
159 outside a handler callback will flush any remaining buffered text
160 (which triggers the "text" event if there is any remaining text).
161 Calling $p->eof inside a handler will terminate parsing at that
163 point and cause $p->parse to return a FALSE value. This also
164 terminates parsing by $p->parse_file().
165 After $p->eof has been called, the parse() and parse_file() methods
167 can be invoked to feed new documents with the parser object.
168 The return value from eof() is a reference to the parser object.
170 Most parser options are controlled by boolean attributes. Each boolean
172 attribute is enabled by calling the corresponding method with a TRUE
173 argument and disabled with a FALSE argument. The attribute value is
174 left unchanged if no argument is given. The return value from each
175 method is the old attribute value.
176 Methods that can be used to get and/or set parser options are:
178 $p->attr_encoded
180 $p->attr_encoded( $bool )
181 By default, the "attr" and @attr argspecs will have general
182 entities for attribute values decoded. Enabling this attribute
183 leaves entities alone.
184 $p->backquote
186 $p->backquote( $bool )
187 By default, only ' and " are recognized as quote characters around
188 attribute values. MSIE also recognizes backquotes for some reason.
189 Enabling this attribute provides compatibility with this behaviour.
190 $p->boolean_attribute_value( $val )
192 This method sets the value reported for boolean attributes inside
193 HTML start tags. By default, the name of the attribute is also
194 used as its value. This affects the values reported for "tokens"
195 and "attr" argspecs.
196 $p->case_sensitive
198 $p->case_sensitive( $bool )
199 By default, tagnames and attribute names are down-cased. Enabling
200 this attribute leaves them as found in the HTML source document.
201 $p->closing_plaintext
203 $p->closing_plaintext( $bool )
204 By default, "plaintext" element can never be closed. Everything up
205 to the end of the document is parsed in CDATA mode. This
206 historical behaviour is what at least MSIE does. Enabling this
207 attribute makes closing "</plaintext>" tag effective and the
208 parsing process will resume after seeing this tag. This emulates
209 early gecko-based browsers.
210 $p->empty_element_tags
212 $p->empty_element_tags( $bool )
213 By default, empty element tags are not recognized as such and the
214 "/" before ">" is just treated like a normal name character (unless
215 "strict_names" is enabled). Enabling this attribute make
216 "HTML::Parser" recognize these tags.
217 Empty element tags look like start tags, but end with the character
219 sequence "/>" instead of ">". When recognized by "HTML::Parser"
220 they cause an artificial end event in addition to the start event.
221 The "text" for the artificial end event will be empty and the
222 "tokenpos" array will be undefined even though the the token array
223 will have one element containing the tag name.
224 $p->marked_sections
226 $p->marked_sections( $bool )
227 By default, section markings like <![CDATA[...]]> are treated like
228 ordinary text. When this attribute is enabled section markings are
229 honoured.
230 There are currently no events associated with the marked section
232 markup, but the text can be returned as "skipped_text".
233 $p->strict_comment
235 $p->strict_comment( $bool )
236 By default, comments are terminated by the first occurrence of
237 "-->". This is the behaviour of most popular browsers (like
238 Mozilla, Opera and MSIE), but it is not correct according to the
239 official HTML standard. Officially, you need an even number of
240 "--" tokens before the closing ">" is recognized and there may not
241 be anything but whitespace between an even and an odd "--".
242 The official behaviour is enabled by enabling this attribute.
244 Enabling of 'strict_comment' also disables recognizing these forms
246 as comments:
247 </ comment>
249 <! comment>
250 $p->strict_end
252 $p->strict_end( $bool )
253 By default, attributes and other junk are allowed to be present on
254 end tags in a manner that emulates MSIE's behaviour.
255 The official behaviour is enabled with this attribute. If enabled,
257 only whitespace is allowed between the tagname and the final ">".
258 $p->strict_names
260 $p->strict_names( $bool )
261 By default, almost anything is allowed in tag and attribute names.
262 This is the behaviour of most popular browsers and allows us to
263 parse some broken tags with invalid attribute values like:
264 <IMG SRC=newprevlstGr.gif ALT=[PREV LIST] BORDER=0>
266 By default, "LIST]" is parsed as a boolean attribute, not as part
268 of the ALT value as was clearly intended. This is also what
269 Mozilla sees.
270 The official behaviour is enabled by enabling this attribute. If
272 enabled, it will cause the tag above to be reported as text since
273 "LIST]" is not a legal attribute name.
274 $p->unbroken_text
276 $p->unbroken_text( $bool )
277 By default, blocks of text are given to the text handler as soon as
278 possible (but the parser takes care always to break text at a
279 boundary between whitespace and non-whitespace so single words and
280 entities can always be decoded safely). This might create breaks
281 that make it hard to do transformations on the text. When this
282 attribute is enabled, blocks of text are always reported in one
283 piece. This will delay the text event until the following (non-
284 text) event has been recognized by the parser.
285 Note that the "offset" argspec will give you the offset of the
287 first segment of text and "length" is the combined length of the
288 segments. Since there might be ignored tags in between, these
289 numbers can't be used to directly index in the original document
290 file.
291 $p->utf8_mode
293 $p->utf8_mode( $bool )
294 Enable this option when parsing raw undecoded UTF-8. This tells
295 the parser that the entities expanded for strings reported by
296 "attr", @attr and "dtext" should be expanded as decoded UTF-8 so
297 they end up compatible with the surrounding text.
298 If "utf8_mode" is enabled then it is an error to pass strings
300 containing characters with code above 255 to the parse() method,
301 and the parse() method will croak if you try.
302 Example: The Unicode character "\x{2665}" is "\xE2\x99\xA5" when
304 UTF-8 encoded. The character can also be represented by the entity
305 "♥" or "♥". If we feed the parser:
306 $p->parse("\xE2\x99\xA5♥");
308 then "dtext" will be reported as "\xE2\x99\xA5\x{2665}" without
310 "utf8_mode" enabled, but as "\xE2\x99\xA5\xE2\x99\xA5" when
311 enabled. The later string is what you want.
312 This option is only available with perl-5.8 or better.
314 $p->xml_mode
316 $p->xml_mode( $bool )
317 Enabling this attribute changes the parser to allow some XML
318 constructs. This enables the behaviour controlled by individually
319 by the "case_sensitive", "empty_element_tags", "strict_names" and
320 "xml_pic" attributes and also suppresses special treatment of
321 elements that are parsed as CDATA for HTML.
322 $p->xml_pic
324 $p->xml_pic( $bool )
325 By default, processing instructions are terminated by ">". When
326 this attribute is enabled, processing instructions are terminated
327 by "?>" instead.
328 As markup and text is recognized, handlers are invoked. The following
330 method is used to set up handlers for different events:
331 $p->handler( event => \&subroutine, $argspec )
333 $p->handler( event => $method_name, $argspec )
334 $p->handler( event => \@accum, $argspec )
335 $p->handler( event => "" );
336 $p->handler( event => undef );
337 $p->handler( event );
338 This method assigns a subroutine, method, or array to handle an
339 event.
340 Event is one of "text", "start", "end", "declaration", "comment",
342 "process", "start_document", "end_document" or "default".
343 The "\&subroutine" is a reference to a subroutine which is called
345 to handle the event.
346 The $method_name is the name of a method of $p which is called to
348 handle the event.
349 The @accum is an array that will hold the event information as sub-
351 arrays.
352 If the second argument is "", the event is ignored. If it is
354 undef, the default handler is invoked for the event.
355 The $argspec is a string that describes the information to be
357 reported for the event. Any requested information that does not
358 apply to a specific event is passed as "undef". If argspec is
359 omitted, then it is left unchanged.
360 The return value from $p->handler is the old callback routine or a
362 reference to the accumulator array.
363 Any return values from handler callback routines/methods are always
365 ignored. A handler callback can request parsing to be aborted by
366 invoking the $p->eof method. A handler callback is not allowed to
367 invoke the $p->parse() or $p->parse_file() method. An exception
368 will be raised if it tries.
369 Examples:
371 $p->handler(start => "start", 'self, attr, attrseq, text' );
373 This causes the "start" method of object $p to be called for
375 'start' events. The callback signature is $p->start(\%attr,
376 \@attr_seq, $text).
377 $p->handler(start => \&start, 'attr, attrseq, text' );
379 This causes subroutine start() to be called for 'start' events.
381 The callback signature is start(\%attr, \@attr_seq, $text).
382 $p->handler(start => \@accum, '"S", attr, attrseq, text' );
384 This causes 'start' event information to be saved in @accum. The
386 array elements will be ['S', \%attr, \@attr_seq, $text].
387 $p->handler(start => "");
389 This causes 'start' events to be ignored. It also suppresses
391 invocations of any default handler for start events. It is in most
392 cases equivalent to $p->handler(start => sub {}), but is more
393 efficient. It is different from the empty-sub-handler in that
394 "skipped_text" is not reset by it.
395 $p->handler(start => undef);
397 This causes no handler to be associated with start events. If
399 there is a default handler it will be invoked.
400 Filters based on tags can be set up to limit the number of events
402 reported. The main bottleneck during parsing is often the huge number
403 of callbacks made from the parser. Applying filters can improve
404 performance significantly.
405 The following methods control filters:
407 $p->ignore_elements( @tags )
409 Both the "start" event and the "end" event as well as any events
410 that would be reported in between are suppressed. The ignored
411 elements can contain nested occurrences of itself. Example:
412 $p->ignore_elements(qw(script style));
414 The "script" and "style" tags will always nest properly since their
416 content is parsed in CDATA mode. For most other tags
417 "ignore_elements" must be used with caution since HTML is often not
418 well formed.
419 $p->ignore_tags( @tags )
421 Any "start" and "end" events involving any of the tags given are
422 suppressed. To reset the filter (i.e. don't suppress any "start"
423 and "end" events), call "ignore_tags" without an argument.
424 $p->report_tags( @tags )
426 Any "start" and "end" events involving any of the tags not given
427 are suppressed. To reset the filter (i.e. report all "start" and
428 "end" events), call "report_tags" without an argument.
429 Internally, the system has two filter lists, one for "report_tags" and
431 one for "ignore_tags", and both filters are applied. This effectively
432 gives "ignore_tags" precedence over "report_tags".
433 Examples:
435 $p->ignore_tags(qw(style));
437 $p->report_tags(qw(script style));
438 results in only "script" events being reported.
440 Argspec
442 Argspec is a string containing a comma-separated list that describes
443 the information reported by the event. The following argspec
444 identifier names can be used:
445 "attr"
447 Attr causes a reference to a hash of attribute name/value pairs to
448 be passed.
449 Boolean attributes' values are either the value set by
451 $p->boolean_attribute_value, or the attribute name if no value has
452 been set by $p->boolean_attribute_value.
453 This passes undef except for "start" events.
455 Unless "xml_mode" or "case_sensitive" is enabled, the attribute
457 names are forced to lower case.
458 General entities are decoded in the attribute values and one layer
460 of matching quotes enclosing the attribute values is removed.
461 The Unicode character set is assumed for entity decoding. With
463 Perl version 5.6 or earlier only the Latin-1 range is supported,
464 and entities for characters outside the range 0..255 are left
465 unchanged.
466 @attr
468 Basically the same as "attr", but keys and values are passed as
469 individual arguments and the original sequence of the attributes is
470 kept. The parameters passed will be the same as the @attr
471 calculated here:
472 @attr = map { $_ => $attr->{$_} } @$attrseq;
474 assuming $attr and $attrseq here are the hash and array passed as
476 the result of "attr" and "attrseq" argspecs.
477 This passes no values for events besides "start".
479 "attrseq"
481 Attrseq causes a reference to an array of attribute names to be
482 passed. This can be useful if you want to walk the "attr" hash in
483 the original sequence.
484 This passes undef except for "start" events.
486 Unless "xml_mode" or "case_sensitive" is enabled, the attribute
488 names are forced to lower case.
489 "column"
491 Column causes the column number of the start of the event to be
492 passed. The first column on a line is 0.
493 "dtext"
495 Dtext causes the decoded text to be passed. General entities are
496 automatically decoded unless the event was inside a CDATA section
497 or was between literal start and end tags ("script", "style",
498 "xmp", "iframe", "title", "textarea" and "plaintext").
499 The Unicode character set is assumed for entity decoding. With
501 Perl version 5.6 or earlier only the Latin-1 range is supported,
502 and entities for characters outside the range 0..255 are left
503 unchanged.
504 This passes undef except for "text" events.
506 "event"
508 Event causes the event name to be passed.
509 The event name is one of "text", "start", "end", "declaration",
511 "comment", "process", "start_document" or "end_document".
512 "is_cdata"
514 Is_cdata causes a TRUE value to be passed if the event is inside a
515 CDATA section or between literal start and end tags ("script",
516 "style", "xmp", "iframe", "title", "textarea" and "plaintext").
517 if the flag is FALSE for a text event, then you should normally
519 either use "dtext" or decode the entities yourself before the text
520 is processed further.
521 "length"
523 Length causes the number of bytes of the source text of the event
524 to be passed.
525 "line"
527 Line causes the line number of the start of the event to be passed.
528 The first line in the document is 1. Line counting doesn't start
529 until at least one handler requests this value to be reported.
530 "offset"
532 Offset causes the byte position in the HTML document of the start
533 of the event to be passed. The first byte in the document has
534 offset 0.
535 "offset_end"
537 Offset_end causes the byte position in the HTML document of the end
538 of the event to be passed. This is the same as "offset" +
539 "length".
540 "self"
542 Self causes the current object to be passed to the handler. If the
543 handler is a method, this must be the first element in the argspec.
544 An alternative to passing self as an argspec is to register
546 closures that capture $self by themselves as handlers.
547 Unfortunately this creates circular references which prevent the
548 HTML::Parser object from being garbage collected. Using the "self"
549 argspec avoids this problem.
550 "skipped_text"
552 Skipped_text returns the concatenated text of all the events that
553 have been skipped since the last time an event was reported.
554 Events might be skipped because no handler is registered for them
555 or because some filter applies. Skipped text also includes marked
556 section markup, since there are no events that can catch it.
557 If an ""-handler is registered for an event, then the text for this
559 event is not included in "skipped_text". Skipped text both before
560 and after the ""-event is included in the next reported
561 "skipped_text".
562 "tag"
564 Same as "tagname", but prefixed with "/" if it belongs to an "end"
565 event and "!" for a declaration. The "tag" does not have any
566 prefix for "start" events, and is in this case identical to
567 "tagname".
568 "tagname"
570 This is the element name (or generic identifier in SGML jargon) for
571 start and end tags. Since HTML is case insensitive, this name is
572 forced to lower case to ease string matching.
573 Since XML is case sensitive, the tagname case is not changed when
575 "xml_mode" is enabled. The same happens if the "case_sensitive"
576 attribute is set.
577 The declaration type of declaration elements is also passed as a
579 tagname, even if that is a bit strange. In fact, in the current
580 implementation tagname is identical to "token0" except that the
581 name may be forced to lower case.
582 "token0"
584 Token0 causes the original text of the first token string to be
585 passed. This should always be the same as $tokens->[0].
586 For "declaration" events, this is the declaration type.
588 For "start" and "end" events, this is the tag name.
590 For "process" and non-strict "comment" events, this is everything
592 inside the tag.
593 This passes undef if there are no tokens in the event.
595 "tokenpos"
597 Tokenpos causes a reference to an array of token positions to be
598 passed. For each string that appears in "tokens", this array
599 contains two numbers. The first number is the offset of the start
600 of the token in the original "text" and the second number is the
601 length of the token.
602 Boolean attributes in a "start" event will have (0,0) for the
604 attribute value offset and length.
605 This passes undef if there are no tokens in the event (e.g.,
607 "text") and for artificial "end" events triggered by empty element
608 tags.
609 If you are using these offsets and lengths to modify "text", you
611 should either work from right to left, or be very careful to
612 calculate the changes to the offsets.
613 "tokens"
615 Tokens causes a reference to an array of token strings to be
616 passed. The strings are exactly as they were found in the original
617 text, no decoding or case changes are applied.
618 For "declaration" events, the array contains each word, comment,
620 and delimited string starting with the declaration type.
621 For "comment" events, this contains each sub-comment. If
623 $p->strict_comments is disabled, there will be only one sub-
624 comment.
625 For "start" events, this contains the original tag name followed by
627 the attribute name/value pairs. The values of boolean attributes
628 will be either the value set by $p->boolean_attribute_value, or the
629 attribute name if no value has been set by
630 $p->boolean_attribute_value.
631 For "end" events, this contains the original tag name (always one
633 token).
634 For "process" events, this contains the process instructions
636 (always one token).
637 This passes "undef" for "text" events.
639 "text"
641 Text causes the source text (including markup element delimiters)
642 to be passed.
643 "undef"
645 Pass an undefined value. Useful as padding where the same handler
646 routine is registered for multiple events.
647 '...'
649 A literal string of 0 to 255 characters enclosed in single (') or
650 double (") quotes is passed as entered.
651 The whole argspec string can be wrapped up in '@{...}' to signal that
653 the resulting event array should be flattened. This only makes a
654 difference if an array reference is used as the handler target.
655 Consider this example:
656 $p->handler(text => [], 'text');
658 $p->handler(text => [], '@{text}']);
659 With two text events; "foo", "bar"; then the first example will end up
661 with [["foo"], ["bar"]] and the second with ["foo", "bar"] in the
662 handler target array.
663 Events
665 Handlers for the following events can be registered:
666 "comment"
668 This event is triggered when a markup comment is recognized.
669 Example:
671 <!-- This is a comment -- -- So is this -->
673 "declaration"
675 This event is triggered when a markup declaration is recognized.
676 For typical HTML documents, the only declaration you are likely to
678 find is <!DOCTYPE ...>.
679 Example:
681 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
683 "http://www.w3.org/TR/html4/strict.dtd">
684 DTDs inside <!DOCTYPE ...> will confuse HTML::Parser.
686 "default"
688 This event is triggered for events that do not have a specific
689 handler. You can set up a handler for this event to catch stuff
690 you did not want to catch explicitly.
691 "end"
693 This event is triggered when an end tag is recognized.
694 Example:
696 </A>
698 "end_document"
700 This event is triggered when $p->eof is called and after any
701 remaining text is flushed. There is no document text associated
702 with this event.
703 "process"
705 This event is triggered when a processing instructions markup is
706 recognized.
707 The format and content of processing instructions are system and
709 application dependent.
710 Examples:
712 <? HTML processing instructions >
714 <? XML processing instructions ?>
715 "start"
717 This event is triggered when a start tag is recognized.
718 Example:
720 <A HREF="http://www.perl.com/">
722 "start_document"
724 This event is triggered before any other events for a new document.
725 A handler for it can be used to initialize stuff. There is no
726 document text associated with this event.
727 "text"
729 This event is triggered when plain text (characters) is recognized.
730 The text may contain multiple lines. A sequence of text may be
731 broken between several text events unless $p->unbroken_text is
732 enabled.
733 The parser will make sure that it does not break a word or a
735 sequence of whitespace between two text events.
736 Unicode
738 "HTML::Parser" can parse Unicode strings when running under perl-5.8 or
739 better. If Unicode is passed to $p->parse() then chunks of Unicode
740 will be reported to the handlers. The offset and length argspecs will
741 also report their position in terms of characters.
742 It is safe to parse raw undecoded UTF-8 if you either avoid decoding
744 entities and make sure to not use argspecs that do, or enable the
745 "utf8_mode" for the parser. Parsing of undecoded UTF-8 might be useful
746 when parsing from a file where you need the reported offsets and
747 lengths to match the byte offsets in the file.
748 If a filename is passed to $p->parse_file() then the file will be read
750 in binary mode. This will be fine if the file contains only ASCII or
751 Latin-1 characters. If the file contains UTF-8 encoded text then care
752 must be taken when decoding entities as described in the previous
753 paragraph, but better is to open the file with the UTF-8 layer so that
754 it is decoded properly:
755 open(my $fh, "<:utf8", "index.html") || die "...: $!";
757 $p->parse_file($fh);
758 If the file contains text encoded in a charset besides ASCII, Latin-1
760 or UTF-8 then decoding will always be needed.
761
763 When an "HTML::Parser" object is constructed with no arguments, a set
764 of handlers is automatically provided that is compatible with the old
765 HTML::Parser version 2 callback methods.
766 This is equivalent to the following method calls:
768 $p->handler(start => "start", "self, tagname, attr, attrseq, text");
770 $p->handler(end => "end", "self, tagname, text");
771 $p->handler(text => "text", "self, text, is_cdata");
772 $p->handler(process => "process", "self, token0, text");
773 $p->handler(comment =>
774 sub {
775 my($self, $tokens) = @_;
776 for (@$tokens) {$self->comment($_);}},
777 "self, tokens");
778 $p->handler(declaration =>
779 sub {
780 my $self = shift;
781 $self->declaration(substr($_[0], 2, -1));},
782 "self, text");
783 Setting up these handlers can also be requested with the "api_version
785 => 2" constructor option.
786
788 The "HTML::Parser" class is subclassable. Parser objects are plain
789 hashes and "HTML::Parser" reserves only hash keys that start with
790 "_hparser". The parser state can be set up by invoking the init()
791 method, which takes the same arguments as new().
792
794 The first simple example shows how you might strip out comments from an
795 HTML document. We achieve this by setting up a comment handler that
796 does nothing and a default handler that will print out anything else:
797 use HTML::Parser;
799 HTML::Parser->new(default_h => [sub { print shift }, 'text'],
800 comment_h => [""],
801 )->parse_file(shift || die) || die $!;
802 An alternative implementation is:
804 use HTML::Parser;
806 HTML::Parser->new(end_document_h => [sub { print shift },
807 'skipped_text'],
808 comment_h => [""],
809 )->parse_file(shift || die) || die $!;
810 This will in most cases be much more efficient since only a single
812 callback will be made.
813 The next example prints out the text that is inside the <title> element
815 of an HTML document. Here we start by setting up a start handler.
816 When it sees the title start tag it enables a text handler that prints
817 any text found and an end handler that will terminate parsing as soon
818 as the title end tag is seen:
819 use HTML::Parser ();
821 sub start_handler
823 {
824 return if shift ne "title";
825 my $self = shift;
826 $self->handler(text => sub { print shift }, "dtext");
827 $self->handler(end => sub { shift->eof if shift eq "title"; },
828 "tagname,self");
829 }
830 my $p = HTML::Parser->new(api_version => 3);
832 $p->handler( start => \&start_handler, "tagname,self");
833 $p->parse_file(shift || die) || die $!;
834 print "\n";
835 More examples are found in the eg/ directory of the "HTML-Parser"
837 distribution: the program "hrefsub" shows how you can edit all links
838 found in a document; the program "htextsub" shows how to edit the text
839 only; the program "hstrip" shows how you can strip out certain
840 tags/elements and/or attributes; and the program "htext" show how to
841 obtain the plain text, but not any script/style content.
842 You can browse the eg/ directory online from the [Browse] link on the
844 http://search.cpan.org/~gaas/HTML-Parser/ page.
845
847 The <style> and <script> sections do not end with the first "</", but
848 need the complete corresponding end tag. The standard behaviour is not
849 really practical.
850 When the strict_comment option is enabled, we still recognize comments
852 where there is something other than whitespace between even and odd
853 "--" markers.
854 Once $p->boolean_attribute_value has been set, there is no way to
856 restore the default behaviour.
857 There is currently no way to get both quote characters into the same
859 literal argspec.
860 Empty tags, e.g. "<>" and "</>", are not recognized. SGML allows them
862 to repeat the previous start tag or close the previous start tag
863 respectively.
864 NET tags, e.g. "code/.../" are not recognized. This is SGML shorthand
866 for "<code>...</code>".
867 Unclosed start or end tags, e.g. "<tt<b>...</b</tt>" are not
869 recognized.
870
872 The following messages may be produced by HTML::Parser. The notation
873 in this listing is the same as used in perldiag:
874 Not a reference to a hash
876 (F) The object blessed into or subclassed from HTML::Parser is not
877 a hash as required by the HTML::Parser methods.
878 Bad signature in parser state object at %p
880 (F) The _hparser_xs_state element does not refer to a valid state
881 structure. Something must have changed the internal value stored
882 in this hash element, or the memory has been overwritten.
883 _hparser_xs_state element is not a reference
885 (F) The _hparser_xs_state element has been destroyed.
886 Can't find '_hparser_xs_state' element in HTML::Parser hash
888 (F) The _hparser_xs_state element is missing from the parser hash.
889 It was either deleted, or not created when the object was created.
890 API version %s not supported by HTML::Parser %s
892 (F) The constructor option 'api_version' with an argument greater
893 than or equal to 4 is reserved for future extensions.
894 Bad constructor option '%s'
896 (F) An unknown constructor option key was passed to the new() or
897 init() methods.
898 Parse loop not allowed
900 (F) A handler invoked the parse() or parse_file() method. This is
901 not permitted.
902 marked sections not supported
904 (F) The $p->marked_sections() method was invoked in a HTML::Parser
905 module that was compiled without support for marked sections.
906 Unknown boolean attribute (%d)
908 (F) Something is wrong with the internal logic that set up aliases
909 for boolean attributes.
910 Only code or array references allowed as handler
912 (F) The second argument for $p->handler must be either a subroutine
913 reference, then name of a subroutine or method, or a reference to
914 an array.
915 No handler for %s events
917 (F) The first argument to $p->handler must be a valid event name;
918 i.e. one of "start", "end", "text", "process", "declaration" or
919 "comment".
920 Unrecognized identifier %s in argspec
922 (F) The identifier is not a known argspec name. Use one of the
923 names mentioned in the argspec section above.
924 Literal string is longer than 255 chars in argspec
926 (F) The current implementation limits the length of literals in an
927 argspec to 255 characters. Make the literal shorter.
928 Backslash reserved for literal string in argspec
930 (F) The backslash character "\" is not allowed in argspec literals.
931 It is reserved to permit quoting inside a literal in a later
932 version.
933 Unterminated literal string in argspec
935 (F) The terminating quote character for a literal was not found.
936 Bad argspec (%s)
938 (F) Only identifier names, literals, spaces and commas are allowed
939 in argspecs.
940 Missing comma separator in argspec
942 (F) Identifiers in an argspec must be separated with ",".
943 Parsing of undecoded UTF-8 will give garbage when decoding entities
945 (W) The first chunk parsed appears to contain undecoded UTF-8 and
946 one or more argspecs that decode entities are used for the callback
947 handlers.
948 The result of decoding will be a mix of encoded and decoded
950 characters for any entities that expand to characters with code
951 above 127. This is not a good thing.
952 The solution is to use the Encode::encode_utf8() on the data before
954 feeding it to the $p->parse(). For $p->parse_file() pass a file
955 that has been opened in ":utf8" mode.
956 The parser can process raw undecoded UTF-8 sanely if the
958 "utf8_mode" is enabled or if the "attr", "@attr" or "dtext"
959 argspecs is avoided.
960 Parsing string decoded with wrong endianness
962 (W) The first character in the document is U+FFFE. This is not a
963 legal Unicode character but a byte swapped BOM. The result of
964 parsing will likely be garbage.
965 Parsing of undecoded UTF-32
967 (W) The parser found the Unicode UTF-32 BOM signature at the start
968 of the document. The result of parsing will likely be garbage.
969 Parsing of undecoded UTF-16
971 (W) The parser found the Unicode UTF-16 BOM signature at the start
972 of the document. The result of parsing will likely be garbage.
973
975 HTML::Entities, HTML::PullParser, HTML::TokeParser, HTML::HeadParser,
976 HTML::LinkExtor, HTML::Form
977 HTML::TreeBuilder (part of the HTML-Tree distribution)
979 <http://www.w3.org/TR/html4/>
981 More information about marked sections and processing instructions may
983 be found at http://www.is-thought.co.uk/book/sgml-8.htm <http://www.is-
984 thought.co.uk/book/sgml-8.htm>.
985
987 Copyright 1996-2008 Gisle Aas. All rights reserved.
988 Copyright 1999-2000 Michael A. Chase. All rights reserved.
989 This library is free software; you can redistribute it and/or modify it
991 under the same terms as Perl itself.
992perl v5.12.1 2010-09-01 Parser(3)