1HTML::Parser(3)       User Contributed Perl Documentation      HTML::Parser(3)
2
3
4

NAME

6       HTML::Parser - HTML parser class
7

SYNOPSIS

9         use strict;
10         use warnings;
11         use HTML::Parser ();
12
13         # Create parser object
14         my $p = HTML::Parser->new(
15           api_version => 3,
16           start_h => [\&start, "tagname, attr"],
17           end_h   => [\&end,   "tagname"],
18           marked_sections => 1,
19         );
20
21         # Parse document text chunk by chunk
22         $p->parse($chunk1);
23         $p->parse($chunk2);
24         # ...
25         # signal end of document
26         $p->eof;
27
28         # Parse directly from file
29         $p->parse_file("foo.html");
30         # or
31         open(my $fh, "<:utf8", "foo.html") || die;
32         $p->parse_file($fh);
33

DESCRIPTION

35       Objects of the "HTML::Parser" class will recognize markup and separate
36       it from plain text (alias data content) in HTML documents.  As
37       different kinds of markup and text are recognized, the corresponding
38       event handlers are invoked.
39
40       "HTML::Parser" is not a generic SGML parser.  We have tried to make it
41       able to deal with the HTML that is actually "out there", and it
42       normally parses as closely as possible to the way the popular web
43       browsers do it instead of strictly following one of the many HTML
44       specifications from W3C.  Where there is disagreement, there is often
45       an option that you can enable to get the official behaviour.
46
47       The document to be parsed may be supplied in arbitrary chunks.  This
48       makes on-the-fly parsing as documents are received from the network
49       possible.
50
51       If event driven parsing does not feel right for your application, you
52       might want to use "HTML::PullParser".  This is an "HTML::Parser"
53       subclass that allows a more conventional program structure.
54

METHODS

56       The following method is used to construct a new "HTML::Parser" object:
57
58       $p = HTML::Parser->new( %options_and_handlers )
59           This class method creates a new "HTML::Parser" object and returns
60           it.  Key/value argument pairs may be provided to assign event
61           handlers or initialize parser options.  The handlers and parser
62           options can also be set or modified later by the method calls
63           described below.
64
65           If a top level key is in the form "<event>_h" (e.g., "text_h") then
66           it assigns a handler to that event, otherwise it initializes a
67           parser option. The event handler specification value must be an
68           array reference.  Multiple handlers may also be assigned with the
69           'handlers => [%handlers]' option.  See examples below.
70
71           If new() is called without any arguments, it will create a parser
72           that uses callback methods compatible with version 2 of
73           "HTML::Parser".  See the section on "version 2 compatibility" below
74           for details.
75
76           The special constructor option 'api_version => 2' can be used to
77           initialize version 2 callbacks while still setting other options
78           and handlers.  The 'api_version => 3' option can be used if you
79           don't want to set any options and don't want to fall back to v2
80           compatible mode.
81
82           Examples:
83
84            $p = HTML::Parser->new(
85              api_version => 3,
86              text_h => [ sub {...}, "dtext" ]
87            );
88
89           This creates a new parser object with a text event handler
90           subroutine that receives the original text with general entities
91           decoded.
92
93            $p = HTML::Parser->new(
94              api_version => 3,
95              start_h => [ 'my_start', "self,tokens" ]
96            );
97
98           This creates a new parser object with a start event handler method
99           that receives the $p and the tokens array.
100
101            $p = HTML::Parser->new(
102              api_version => 3,
103              handlers => {
104                text => [\@array, "event,text"],
105                comment => [\@array, "event,text"],
106              }
107            );
108
109           This creates a new parser object that stores the event type and the
110           original text in @array for text and comment events.
111
112       The following methods feed the HTML document to the "HTML::Parser"
113       object:
114
115       $p->parse( $string )
116           Parse $string as the next chunk of the HTML document.  Handlers
117           invoked should not attempt to modify the $string in-place until
118           $p->parse returns.
119
120           If an invoked event handler aborts parsing by calling $p->eof, then
121           $p->parse() will return a FALSE value.  Otherwise the return value
122           is a reference to the parser object ($p).
123
124       $p->parse( $code_ref )
125           If a code reference is passed as the argument to be parsed, then
126           the chunks to be parsed are obtained by invoking this function
127           repeatedly.  Parsing continues until the function returns an empty
128           (or undefined) result.  When this happens $p->eof is automatically
129           signaled.
130
131           Parsing will also abort if one of the event handlers calls $p->eof.
132
133           The effect of this is the same as:
134
135             while (1) {
136               my $chunk = &$code_ref();
137               if (!defined($chunk) || !length($chunk)) {
138                 $p->eof;
139                 return $p;
140               }
141               $p->parse($chunk) || return undef;
142             }
143
144           But it is more efficient as this loop runs internally in XS code.
145
146       $p->parse_file( $file )
147           Parse text directly from a file.  The $file argument can be a
148           filename, an open file handle, or a reference to an open file
149           handle.
150
151           If $file contains a filename and the file can't be opened, then the
152           method returns an undefined value and $! tells why it failed.
153           Otherwise the return value is a reference to the parser object.
154
155           If a file handle is passed as the $file argument, then the file
156           will normally be read until EOF, but not closed.
157
158           If an invoked event handler aborts parsing by calling $p->eof, then
159           $p->parse_file() may not have read the entire file.
160
161           On systems with multi-byte line terminators, the values passed for
162           the offset and length argspecs may be too low if parse_file() is
163           called on a file handle that is not in binary mode.
164
165           If a filename is passed in, then parse_file() will open the file in
166           binary mode.
167
168       $p->eof
169           Signals the end of the HTML document.  Calling the $p->eof method
170           outside a handler callback will flush any remaining buffered text
171           (which triggers the "text" event if there is any remaining text).
172
173           Calling $p->eof inside a handler will terminate parsing at that
174           point and cause $p->parse to return a FALSE value.  This also
175           terminates parsing by $p->parse_file().
176
177           After $p->eof has been called, the parse() and parse_file() methods
178           can be invoked to feed new documents with the parser object.
179
180           The return value from eof() is a reference to the parser object.
181
182       Most parser options are controlled by boolean attributes.  Each boolean
183       attribute is enabled by calling the corresponding method with a TRUE
184       argument and disabled with a FALSE argument.  The attribute value is
185       left unchanged if no argument is given.  The return value from each
186       method is the old attribute value.
187
188       Methods that can be used to get and/or set parser options are:
189
190       $p->attr_encoded
191       $p->attr_encoded( $bool )
192           By default, the "attr" and @attr argspecs will have general
193           entities for attribute values decoded.  Enabling this attribute
194           leaves entities alone.
195
196       $p->backquote
197       $p->backquote( $bool )
198           By default, only ' and " are recognized as quote characters around
199           attribute values.  MSIE also recognizes backquotes for some reason.
200           Enabling this attribute provides compatibility with this behaviour.
201
202       $p->boolean_attribute_value( $val )
203           This method sets the value reported for boolean attributes inside
204           HTML start tags.  By default, the name of the attribute is also
205           used as its value.  This affects the values reported for "tokens"
206           and "attr" argspecs.
207
208       $p->case_sensitive
209       $p->case_sensitive( $bool )
210           By default, tag names and attribute names are down-cased.  Enabling
211           this attribute leaves them as found in the HTML source document.
212
213       $p->closing_plaintext
214       $p->closing_plaintext( $bool )
215           By default, "plaintext" element can never be closed. Everything up
216           to the end of the document is parsed in CDATA mode.  This
217           historical behaviour is what at least MSIE does.  Enabling this
218           attribute makes closing " </plaintext" > tag effective and the
219           parsing process will resume after seeing this tag.  This emulates
220           early gecko-based browsers.
221
222       $p->empty_element_tags
223       $p->empty_element_tags( $bool )
224           By default, empty element tags are not recognized as such and the
225           "/" before ">" is just treated like a normal name character (unless
226           "strict_names" is enabled).  Enabling this attribute make
227           "HTML::Parser" recognize these tags.
228
229           Empty element tags look like start tags, but end with the character
230           sequence "/>" instead of ">".  When recognized by "HTML::Parser"
231           they cause an artificial end event in addition to the start event.
232           The "text" for the artificial end event will be empty and the
233           "tokenpos" array will be undefined even though the token array will
234           have one element containing the tag name.
235
236       $p->marked_sections
237       $p->marked_sections( $bool )
238           By default, section markings like <![CDATA[...]]> are treated like
239           ordinary text.  When this attribute is enabled section markings are
240           honoured.
241
242           There are currently no events associated with the marked section
243           markup, but the text can be returned as "skipped_text".
244
245       $p->strict_comment
246       $p->strict_comment( $bool )
247           By default, comments are terminated by the first occurrence of
248           "-->".  This is the behaviour of most popular browsers (like
249           Mozilla, Opera and MSIE), but it is not correct according to the
250           official HTML standard.  Officially, you need an even number of
251           "--" tokens before the closing ">" is recognized and there may not
252           be anything but whitespace between an even and an odd "--".
253
254           The official behaviour is enabled by enabling this attribute.
255
256           Enabling of 'strict_comment' also disables recognizing these forms
257           as comments:
258
259             </ comment>
260             <! comment>
261
262       $p->strict_end
263       $p->strict_end( $bool )
264           By default, attributes and other junk are allowed to be present on
265           end tags in a manner that emulates MSIE's behaviour.
266
267           The official behaviour is enabled with this attribute.  If enabled,
268           only whitespace is allowed between the tagname and the final ">".
269
270       $p->strict_names
271       $p->strict_names( $bool )
272           By default, almost anything is allowed in tag and attribute names.
273           This is the behaviour of most popular browsers and allows us to
274           parse some broken tags with invalid attribute values like:
275
276              <IMG SRC=newprevlstGr.gif ALT=[PREV LIST] BORDER=0>
277
278           By default, "LIST]" is parsed as a boolean attribute, not as part
279           of the ALT value as was clearly intended.  This is also what
280           Mozilla sees.
281
282           The official behaviour is enabled by enabling this attribute.  If
283           enabled, it will cause the tag above to be reported as text since
284           "LIST]" is not a legal attribute name.
285
286       $p->unbroken_text
287       $p->unbroken_text( $bool )
288           By default, blocks of text are given to the text handler as soon as
289           possible (but the parser takes care always to break text at a
290           boundary between whitespace and non-whitespace so single words and
291           entities can always be decoded safely).  This might create breaks
292           that make it hard to do transformations on the text. When this
293           attribute is enabled, blocks of text are always reported in one
294           piece.  This will delay the text event until the following (non-
295           text) event has been recognized by the parser.
296
297           Note that the "offset" argspec will give you the offset of the
298           first segment of text and "length" is the combined length of the
299           segments.  Since there might be ignored tags in between, these
300           numbers can't be used to directly index in the original document
301           file.
302
303       $p->utf8_mode
304       $p->utf8_mode( $bool )
305           Enable this option when parsing raw undecoded UTF-8.  This tells
306           the parser that the entities expanded for strings reported by
307           "attr", @attr and "dtext" should be expanded as decoded UTF-8 so
308           they end up compatible with the surrounding text.
309
310           If "utf8_mode" is enabled then it is an error to pass strings
311           containing characters with code above 255 to the parse() method,
312           and the parse() method will croak if you try.
313
314           Example: The Unicode character "\x{2665}" is "\xE2\x99\xA5" when
315           UTF-8 encoded.  The character can also be represented by the entity
316           "&hearts;" or "&#x2665".  If we feed the parser:
317
318             $p->parse("\xE2\x99\xA5&hearts;");
319
320           then "dtext" will be reported as "\xE2\x99\xA5\x{2665}" without
321           "utf8_mode" enabled, but as "\xE2\x99\xA5\xE2\x99\xA5" when
322           enabled.  The later string is what you want.
323
324           This option is only available with perl-5.8 or better.
325
326       $p->xml_mode
327       $p->xml_mode( $bool )
328           Enabling this attribute changes the parser to allow some XML
329           constructs.  This enables the behaviour controlled by individually
330           by the "case_sensitive", "empty_element_tags", "strict_names" and
331           "xml_pic" attributes and also suppresses special treatment of
332           elements that are parsed as CDATA for HTML.
333
334       $p->xml_pic
335       $p->xml_pic( $bool )
336           By default, processing instructions are terminated by ">". When
337           this attribute is enabled, processing instructions are terminated
338           by "?>" instead.
339
340       As markup and text is recognized, handlers are invoked.  The following
341       method is used to set up handlers for different events:
342
343       $p->handler( event => \&subroutine, $argspec )
344       $p->handler( event => $method_name, $argspec )
345       $p->handler( event => \@accum, $argspec )
346       $p->handler( event => "" );
347       $p->handler( event => undef );
348       $p->handler( event );
349           This method assigns a subroutine, method, or array to handle an
350           event.
351
352           Event is one of "text", "start", "end", "declaration", "comment",
353           "process", "start_document", "end_document" or "default".
354
355           The "\&subroutine" is a reference to a subroutine which is called
356           to handle the event.
357
358           The $method_name is the name of a method of $p which is called to
359           handle the event.
360
361           The @accum is an array that will hold the event information as sub-
362           arrays.
363
364           If the second argument is "", the event is ignored.  If it is
365           undef, the default handler is invoked for the event.
366
367           The $argspec is a string that describes the information to be
368           reported for the event.  Any requested information that does not
369           apply to a specific event is passed as "undef".  If argspec is
370           omitted, then it is left unchanged.
371
372           The return value from $p->handler is the old callback routine or a
373           reference to the accumulator array.
374
375           Any return values from handler callback routines/methods are always
376           ignored.  A handler callback can request parsing to be aborted by
377           invoking the $p->eof method.  A handler callback is not allowed to
378           invoke the $p->parse() or $p->parse_file() method.  An exception
379           will be raised if it tries.
380
381           Examples:
382
383               $p->handler(start =>  "start", 'self, attr, attrseq, text' );
384
385           This causes the "start" method of object $p to be called for
386           'start' events.  The callback signature is "$p->start(\%attr,
387           \@attr_seq, $text)".
388
389               $p->handler(start =>  \&start, 'attr, attrseq, text' );
390
391           This causes subroutine start() to be called for 'start' events.
392           The callback signature is start(\%attr, \@attr_seq, $text).
393
394               $p->handler(start =>  \@accum, '"S", attr, attrseq, text' );
395
396           This causes 'start' event information to be saved in @accum.  The
397           array elements will be ['S', \%attr, \@attr_seq, $text].
398
399              $p->handler(start => "");
400
401           This causes 'start' events to be ignored.  It also suppresses
402           invocations of any default handler for start events.  It is in most
403           cases equivalent to $p->handler(start => sub {}), but is more
404           efficient.  It is different from the empty-sub-handler in that
405           "skipped_text" is not reset by it.
406
407              $p->handler(start => undef);
408
409           This causes no handler to be associated with start events.  If
410           there is a default handler it will be invoked.
411
412       Filters based on tags can be set up to limit the number of events
413       reported.  The main bottleneck during parsing is often the huge number
414       of callbacks made from the parser.  Applying filters can improve
415       performance significantly.
416
417       The following methods control filters:
418
419       $p->ignore_elements( @tags )
420           Both the "start" event and the "end" event as well as any events
421           that would be reported in between are suppressed.  The ignored
422           elements can contain nested occurrences of itself.  Example:
423
424              $p->ignore_elements(qw(script style));
425
426           The "script" and "style" tags will always nest properly since their
427           content is parsed in CDATA mode.  For most other tags
428           "ignore_elements" must be used with caution since HTML is often not
429           well formed.
430
431       $p->ignore_tags( @tags )
432           Any "start" and "end" events involving any of the tags given are
433           suppressed.  To reset the filter (i.e. don't suppress any "start"
434           and "end" events), call "ignore_tags" without an argument.
435
436       $p->report_tags( @tags )
437           Any "start" and "end" events involving any of the tags not given
438           are suppressed.  To reset the filter (i.e. report all "start" and
439           "end" events), call "report_tags" without an argument.
440
441       Internally, the system has two filter lists, one for "report_tags" and
442       one for "ignore_tags", and both filters are applied.  This effectively
443       gives "ignore_tags" precedence over "report_tags".
444
445       Examples:
446
447          $p->ignore_tags(qw(style));
448          $p->report_tags(qw(script style));
449
450       results in only "script" events being reported.
451
452   Argspec
453       Argspec is a string containing a comma-separated list that describes
454       the information reported by the event.  The following argspec
455       identifier names can be used:
456
457       "attr"
458           Attr causes a reference to a hash of attribute name/value pairs to
459           be passed.
460
461           Boolean attributes' values are either the value set by
462           $p->boolean_attribute_value, or the attribute name if no value has
463           been set by $p->boolean_attribute_value.
464
465           This passes undef except for "start" events.
466
467           Unless "xml_mode" or "case_sensitive" is enabled, the attribute
468           names are forced to lower case.
469
470           General entities are decoded in the attribute values and one layer
471           of matching quotes enclosing the attribute values is removed.
472
473           The Unicode character set is assumed for entity decoding.
474
475       @attr
476           Basically the same as "attr", but keys and values are passed as
477           individual arguments and the original sequence of the attributes is
478           kept.  The parameters passed will be the same as the @attr
479           calculated here:
480
481              @attr = map { $_ => $attr->{$_} } @$attrseq;
482
483           assuming $attr and $attrseq here are the hash and array passed as
484           the result of "attr" and "attrseq" argspecs.
485
486           This passes no values for events besides "start".
487
488       "attrseq"
489           Attrseq causes a reference to an array of attribute names to be
490           passed.  This can be useful if you want to walk the "attr" hash in
491           the original sequence.
492
493           This passes undef except for "start" events.
494
495           Unless "xml_mode" or "case_sensitive" is enabled, the attribute
496           names are forced to lower case.
497
498       "column"
499           Column causes the column number of the start of the event to be
500           passed.  The first column on a line is 0.
501
502       "dtext"
503           Dtext causes the decoded text to be passed.  General entities are
504           automatically decoded unless the event was inside a CDATA section
505           or was between literal start and end tags ("script", "style",
506           "xmp", "iframe", "title", "textarea" and "plaintext").
507
508           The Unicode character set is assumed for entity decoding.  With
509           Perl version 5.6 or earlier only the Latin-1 range is supported,
510           and entities for characters outside the range 0..255 are left
511           unchanged.
512
513           This passes undef except for "text" events.
514
515       "event"
516           Event causes the event name to be passed.
517
518           The event name is one of "text", "start", "end", "declaration",
519           "comment", "process", "start_document" or "end_document".
520
521       "is_cdata"
522           Is_cdata causes a TRUE value to be passed if the event is inside a
523           CDATA section or between literal start and end tags ("script",
524           "style", "xmp", "iframe", "title", "textarea" and "plaintext").
525
526           if the flag is FALSE for a text event, then you should normally
527           either use "dtext" or decode the entities yourself before the text
528           is processed further.
529
530       "length"
531           Length causes the number of bytes of the source text of the event
532           to be passed.
533
534       "line"
535           Line causes the line number of the start of the event to be passed.
536           The first line in the document is 1.  Line counting doesn't start
537           until at least one handler requests this value to be reported.
538
539       "offset"
540           Offset causes the byte position in the HTML document of the start
541           of the event to be passed.  The first byte in the document has
542           offset 0.
543
544       "offset_end"
545           Offset_end causes the byte position in the HTML document of the end
546           of the event to be passed.  This is the same as "offset" +
547           "length".
548
549       "self"
550           Self causes the current object to be passed to the handler.  If the
551           handler is a method, this must be the first element in the argspec.
552
553           An alternative to passing self as an argspec is to register
554           closures that capture $self by themselves as handlers.
555           Unfortunately this creates circular references which prevent the
556           HTML::Parser object from being garbage collected.  Using the "self"
557           argspec avoids this problem.
558
559       "skipped_text"
560           Skipped_text returns the concatenated text of all the events that
561           have been skipped since the last time an event was reported.
562           Events might be skipped because no handler is registered for them
563           or because some filter applies.  Skipped text also includes marked
564           section markup, since there are no events that can catch it.
565
566           If an ""-handler is registered for an event, then the text for this
567           event is not included in "skipped_text".  Skipped text both before
568           and after the ""-event is included in the next reported
569           "skipped_text".
570
571       "tag"
572           Same as "tagname", but prefixed with "/" if it belongs to an "end"
573           event and "!" for a declaration.  The "tag" does not have any
574           prefix for "start" events, and is in this case identical to
575           "tagname".
576
577       "tagname"
578           This is the element name (or generic identifier in SGML jargon) for
579           start and end tags.  Since HTML is case insensitive, this name is
580           forced to lower case to ease string matching.
581
582           Since XML is case sensitive, the tagname case is not changed when
583           "xml_mode" is enabled.  The same happens if the "case_sensitive"
584           attribute is set.
585
586           The declaration type of declaration elements is also passed as a
587           tagname, even if that is a bit strange.  In fact, in the current
588           implementation tagname is identical to "token0" except that the
589           name may be forced to lower case.
590
591       "token0"
592           Token0 causes the original text of the first token string to be
593           passed.  This should always be the same as $tokens->[0].
594
595           For "declaration" events, this is the declaration type.
596
597           For "start" and "end" events, this is the tag name.
598
599           For "process" and non-strict "comment" events, this is everything
600           inside the tag.
601
602           This passes undef if there are no tokens in the event.
603
604       "tokenpos"
605           Tokenpos causes a reference to an array of token positions to be
606           passed.  For each string that appears in "tokens", this array
607           contains two numbers.  The first number is the offset of the start
608           of the token in the original "text" and the second number is the
609           length of the token.
610
611           Boolean attributes in a "start" event will have (0,0) for the
612           attribute value offset and length.
613
614           This passes undef if there are no tokens in the event (e.g.,
615           "text") and for artificial "end" events triggered by empty element
616           tags.
617
618           If you are using these offsets and lengths to modify "text", you
619           should either work from right to left, or be very careful to
620           calculate the changes to the offsets.
621
622       "tokens"
623           Tokens causes a reference to an array of token strings to be
624           passed.  The strings are exactly as they were found in the original
625           text, no decoding or case changes are applied.
626
627           For "declaration" events, the array contains each word, comment,
628           and delimited string starting with the declaration type.
629
630           For "comment" events, this contains each sub-comment.  If
631           $p->strict_comments is disabled, there will be only one sub-
632           comment.
633
634           For "start" events, this contains the original tag name followed by
635           the attribute name/value pairs.  The values of boolean attributes
636           will be either the value set by $p->boolean_attribute_value, or the
637           attribute name if no value has been set by
638           $p->boolean_attribute_value.
639
640           For "end" events, this contains the original tag name (always one
641           token).
642
643           For "process" events, this contains the process instructions
644           (always one token).
645
646           This passes "undef" for "text" events.
647
648       "text"
649           Text causes the source text (including markup element delimiters)
650           to be passed.
651
652       "undef"
653           Pass an undefined value.  Useful as padding where the same handler
654           routine is registered for multiple events.
655
656       '...'
657           A literal string of 0 to 255 characters enclosed in single (') or
658           double (") quotes is passed as entered.
659
660       The whole argspec string can be wrapped up in '@{...}' to signal that
661       the resulting event array should be flattened.  This only makes a
662       difference if an array reference is used as the handler target.
663       Consider this example:
664
665          $p->handler(text => [], 'text');
666          $p->handler(text => [], '@{text}']);
667
668       With two text events; "foo", "bar"; then the first example will end up
669       with [["foo"], ["bar"]] and the second with ["foo", "bar"] in the
670       handler target array.
671
672   Events
673       Handlers for the following events can be registered:
674
675       "comment"
676           This event is triggered when a markup comment is recognized.
677
678           Example:
679
680             <!-- This is a comment -- -- So is this -->
681
682       "declaration"
683           This event is triggered when a markup declaration is recognized.
684
685           For typical HTML documents, the only declaration you are likely to
686           find is <!DOCTYPE ...>.
687
688           Example:
689
690             <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
691                 "http://www.w3.org/TR/html4/strict.dtd">
692
693           DTDs inside <!DOCTYPE ...> will confuse HTML::Parser.
694
695       "default"
696           This event is triggered for events that do not have a specific
697           handler.  You can set up a handler for this event to catch stuff
698           you did not want to catch explicitly.
699
700       "end"
701           This event is triggered when an end tag is recognized.
702
703           Example:
704
705             </A>
706
707       "end_document"
708           This event is triggered when $p->eof is called and after any
709           remaining text is flushed.  There is no document text associated
710           with this event.
711
712       "process"
713           This event is triggered when a processing instructions markup is
714           recognized.
715
716           The format and content of processing instructions are system and
717           application dependent.
718
719           Examples:
720
721             <? HTML processing instructions >
722             <? XML processing instructions ?>
723
724       "start"
725           This event is triggered when a start tag is recognized.
726
727           Example:
728
729             <A HREF="http://www.perl.com/">
730
731       "start_document"
732           This event is triggered before any other events for a new document.
733           A handler for it can be used to initialize stuff.  There is no
734           document text associated with this event.
735
736       "text"
737           This event is triggered when plain text (characters) is recognized.
738           The text may contain multiple lines.  A sequence of text may be
739           broken between several text events unless $p->unbroken_text is
740           enabled.
741
742           The parser will make sure that it does not break a word or a
743           sequence of whitespace between two text events.
744
745   Unicode
746       "HTML::Parser" can parse Unicode strings when running under perl-5.8 or
747       better.  If Unicode is passed to $p->parse() then chunks of Unicode
748       will be reported to the handlers.  The offset and length argspecs will
749       also report their position in terms of characters.
750
751       It is safe to parse raw undecoded UTF-8 if you either avoid decoding
752       entities and make sure to not use argspecs that do, or enable the
753       "utf8_mode" for the parser.  Parsing of undecoded UTF-8 might be useful
754       when parsing from a file where you need the reported offsets and
755       lengths to match the byte offsets in the file.
756
757       If a filename is passed to $p->parse_file() then the file will be read
758       in binary mode.  This will be fine if the file contains only ASCII or
759       Latin-1 characters.  If the file contains UTF-8 encoded text then care
760       must be taken when decoding entities as described in the previous
761       paragraph, but better is to open the file with the UTF-8 layer so that
762       it is decoded properly:
763
764          open(my $fh, "<:utf8", "index.html") || die "...: $!";
765          $p->parse_file($fh);
766
767       If the file contains text encoded in a charset besides ASCII, Latin-1
768       or UTF-8 then decoding will always be needed.
769

VERSION 2 COMPATIBILITY

771       When an "HTML::Parser" object is constructed with no arguments, a set
772       of handlers is automatically provided that is compatible with the old
773       HTML::Parser version 2 callback methods.
774
775       This is equivalent to the following method calls:
776
777         $p->handler(start   => "start",   "self, tagname, attr, attrseq, text");
778         $p->handler(end     => "end",     "self, tagname, text");
779         $p->handler(text    => "text",    "self, text, is_cdata");
780         $p->handler(process => "process", "self, token0, text");
781         $p->handler(
782           comment => sub {
783             my($self, $tokens) = @_;
784             for (@$tokens) {$self->comment($_);}
785           },
786           "self, tokens"
787         );
788         $p->handler(
789           declaration => sub {
790             my $self = shift;
791             $self->declaration(substr($_[0], 2, -1));
792           },
793           "self, text"
794         );
795
796       Setting up these handlers can also be requested with the "api_version
797       => 2" constructor option.
798

SUBCLASSING

800       The "HTML::Parser" class is able to be subclassed.  Parser objects are
801       plain hashes and "HTML::Parser" reserves only hash keys that start with
802       "_hparser".  The parser state can be set up by invoking the init()
803       method, which takes the same arguments as new().
804

EXAMPLES

806       The first simple example shows how you might strip out comments from an
807       HTML document.  We achieve this by setting up a comment handler that
808       does nothing and a default handler that will print out anything else:
809
810         use HTML::Parser;
811         HTML::Parser->new(
812           default_h => [sub { print shift }, 'text'],
813           comment_h => [""],
814         )->parse_file(shift || die) || die $!;
815
816       An alternative implementation is:
817
818         use HTML::Parser;
819         HTML::Parser->new(
820           end_document_h => [sub { print shift }, 'skipped_text'],
821           comment_h      => [""],
822         )->parse_file(shift || die) || die $!;
823
824       This will in most cases be much more efficient since only a single
825       callback will be made.
826
827       The next example prints out the text that is inside the <title> element
828       of an HTML document.  Here we start by setting up a start handler.
829       When it sees the title start tag it enables a text handler that prints
830       any text found and an end handler that will terminate parsing as soon
831       as the title end tag is seen:
832
833         use HTML::Parser ();
834
835         sub start_handler {
836           return if shift ne "title";
837           my $self = shift;
838           $self->handler(text => sub { print shift }, "dtext");
839           $self->handler(
840             end  => sub {
841               shift->eof if shift eq "title";
842             },
843             "tagname,self"
844           );
845         }
846
847         my $p = HTML::Parser->new(api_version => 3);
848         $p->handler(start => \&start_handler, "tagname,self");
849         $p->parse_file(shift || die) || die $!;
850         print "\n";
851
852       More examples are found in the eg/ directory of the "HTML-Parser"
853       distribution: the program "hrefsub" shows how you can edit all links
854       found in a document; the program "htextsub" shows how to edit the text
855       only; the program "hstrip" shows how you can strip out certain
856       tags/elements and/or attributes; and the program "htext" show how to
857       obtain the plain text, but not any script/style content.
858
859       You can browse the eg/ directory online from the [Browse] link on the
860       http://search.cpan.org/~gaas/HTML-Parser/ page.
861

BUGS

863       The <style> and <script> sections do not end with the first "</", but
864       need the complete corresponding end tag.  The standard behaviour is not
865       really practical.
866
867       When the strict_comment option is enabled, we still recognize comments
868       where there is something other than whitespace between even and odd
869       "--" markers.
870
871       Once $p->boolean_attribute_value has been set, there is no way to
872       restore the default behaviour.
873
874       There is currently no way to get both quote characters into the same
875       literal argspec.
876
877       Empty tags, e.g. "<>" and "</>", are not recognized.  SGML allows them
878       to repeat the previous start tag or close the previous start tag
879       respectively.
880
881       NET tags, e.g. "code/.../" are not recognized.  This is SGML shorthand
882       for "<code>...</code>".
883
884       Incomplete start or end tags, e.g. "<tt<b>...</b</tt>" are not
885       recognized.
886

DIAGNOSTICS

888       The following messages may be produced by HTML::Parser.  The notation
889       in this listing is the same as used in perldiag:
890
891       Not a reference to a hash
892           (F) The object blessed into or subclassed from HTML::Parser is not
893           a hash as required by the HTML::Parser methods.
894
895       Bad signature in parser state object at %p
896           (F) The _hparser_xs_state element does not refer to a valid state
897           structure.  Something must have changed the internal value stored
898           in this hash element, or the memory has been overwritten.
899
900       _hparser_xs_state element is not a reference
901           (F) The _hparser_xs_state element has been destroyed.
902
903       Can't find '_hparser_xs_state' element in HTML::Parser hash
904           (F) The _hparser_xs_state element is missing from the parser hash.
905           It was either deleted, or not created when the object was created.
906
907       API version %s not supported by HTML::Parser %s
908           (F) The constructor option 'api_version' with an argument greater
909           than or equal to 4 is reserved for future extensions.
910
911       Bad constructor option '%s'
912           (F) An unknown constructor option key was passed to the new() or
913           init() methods.
914
915       Parse loop not allowed
916           (F) A handler invoked the parse() or parse_file() method.  This is
917           not permitted.
918
919       marked sections not supported
920           (F) The $p->marked_sections() method was invoked in a HTML::Parser
921           module that was compiled without support for marked sections.
922
923       Unknown boolean attribute (%d)
924           (F) Something is wrong with the internal logic that set up aliases
925           for boolean attributes.
926
927       Only code or array references allowed as handler
928           (F) The second argument for $p->handler must be either a subroutine
929           reference, then name of a subroutine or method, or a reference to
930           an array.
931
932       No handler for %s events
933           (F) The first argument to $p->handler must be a valid event name;
934           i.e. one of "start", "end", "text", "process", "declaration" or
935           "comment".
936
937       Unrecognized identifier %s in argspec
938           (F) The identifier is not a known argspec name.  Use one of the
939           names mentioned in the argspec section above.
940
941       Literal string is longer than 255 chars in argspec
942           (F) The current implementation limits the length of literals in an
943           argspec to 255 characters.  Make the literal shorter.
944
945       Backslash reserved for literal string in argspec
946           (F) The backslash character "\" is not allowed in argspec literals.
947           It is reserved to permit quoting inside a literal in a later
948           version.
949
950       Unterminated literal string in argspec
951           (F) The terminating quote character for a literal was not found.
952
953       Bad argspec (%s)
954           (F) Only identifier names, literals, spaces and commas are allowed
955           in argspecs.
956
957       Missing comma separator in argspec
958           (F) Identifiers in an argspec must be separated with ",".
959
960       Parsing of undecoded UTF-8 will give garbage when decoding entities
961           (W) The first chunk parsed appears to contain undecoded UTF-8 and
962           one or more argspecs that decode entities are used for the callback
963           handlers.
964
965           The result of decoding will be a mix of encoded and decoded
966           characters for any entities that expand to characters with code
967           above 127.  This is not a good thing.
968
969           The recommended solution is to apply Encode::decode_utf8() on the
970           data before feeding it to the $p->parse().  For $p->parse_file()
971           pass a file that has been opened in ":utf8" mode.
972
973           The alternative solution is to enable the "utf8_mode" and not
974           decode before passing strings to $p->parse().  The parser can
975           process raw undecoded UTF-8 sanely if the "utf8_mode" is enabled,
976           or if the "attr", @attr or "dtext" argspecs are avoided.
977
978       Parsing string decoded with wrong endian selection
979           (W) The first character in the document is U+FFFE.  This is not a
980           legal Unicode character but a byte swapped "BOM".  The result of
981           parsing will likely be garbage.
982
983       Parsing of undecoded UTF-32
984           (W) The parser found the Unicode UTF-32 "BOM" signature at the
985           start of the document.  The result of parsing will likely be
986           garbage.
987
988       Parsing of undecoded UTF-16
989           (W) The parser found the Unicode UTF-16 "BOM" signature at the
990           start of the document.  The result of parsing will likely be
991           garbage.
992

SEE ALSO

994       HTML::Entities, HTML::PullParser, HTML::TokeParser, HTML::HeadParser,
995       HTML::LinkExtor, HTML::Form
996
997       HTML::TreeBuilder (part of the HTML-Tree distribution)
998
999       <http://www.w3.org/TR/html4/>
1000
1001       More information about marked sections and processing instructions may
1002       be found at <http://www.is-thought.co.uk/book/sgml-8.htm>.
1003
1005        Copyright 1996-2016 Gisle Aas. All rights reserved.
1006        Copyright 1999-2000 Michael A. Chase.  All rights reserved.
1007
1008       This library is free software; you can redistribute it and/or modify it
1009       under the same terms as Perl itself.
1010
1011
1012
1013perl v5.32.0                      2020-09-10                   HTML::Parser(3)
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