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Parser(3) User Contributed Perl Documentation Parser(3)

NAME

HTML::Parser - HTML parser class

SYNOPSIS

use HTML::Parser ();

# Create parser object

$p = HTML::Parser->new( apiversion => 3,

starth => [\&start, "tagname, attr"], endh => [\&end, "tagname"], markedsections => 1, );

# Parse document text chunk by chunk

$p->parse($chunk1);

$p->parse($chunk2);

#...

$p->eof; # signal end of document

# Parse directly from file

$p->parsefile("foo.html");

# or

open(my $fh, "<:utf8", "foo.html") || die;

$p->parsefile($fh);

DESCRIPTION

Objects of the "HTML::Parser" class will recognize markup and separate

it from plain text (alias data content) in HTML documents. As different kinds of markup and text are recognized, the corresponding event handlers are invoked.

"HTML::Parser" is not a generic SGML parser. We have tried to make it

able to deal with the HTML that is actually "out there", and it normally parses as closely as possible to the way the popular web browsers do it instead of strictly following one of the many HTML specifications from W3C. Where there is disagreement, there is often an option that you can enable to get the official behaviour. The document to be parsed may be supplied in arbitrary chunks. This

makes on-the-fly parsing as documents are received from the network

possible. If event driven parsing does not feel right for your application, you

might want to use "HTML::PullParser". This is an "HTML::Parser"

subclass that allows a more conventional program structure. MMEETTHHOODDSS

The following method is used to construct a new "HTML::Parser" object:

$p = HTML::Parser->new( %optionsandhandlers )

This class method creates a new "HTML::Parser" object and returns

it. Key/value argument pairs may be provided to assign event handlers or initialize parser options. The handlers and parser options can also be set or modified later by the method calls described below. If a top level key is in the form "h" (e.g., "texth") then it assigns a handler to that event, otherwise it initializes a parser option. The event handler specification value must be an array reference. Multiple handlers may also be assigned with the

'handlers => [%handlers]' option. See examples below.

If new() is called without any arguments, it will create a parser that uses callback methods compatible with version 2 of

"HTML::Parser". See the section on "version 2 compatibility" below

for details. The special constructor option 'apiversion => 2' can be used to initialize version 2 callbacks while still setting other options and handlers. The 'apiversion => 3' option can be used if you don't want to set any options and don't want to fall back to v2 compatible mode. Examples:

$p = HTML::Parser->new(apiversion => 3,

texth => [ sub {...}, "dtext" ]); This creates a new parser object with a text event handler subroutine that receives the original text with general entities decoded.

$p = HTML::Parser->new(apiversion => 3,

starth => [ 'mystart', "self,tokens" ]); This creates a new parser object with a start event handler method

that receives the $p and the tokens array.

$p = HTML::Parser->new(apiversion => 3,

handlers => { text => [\@array, "event,text"], comment => [\@array, "event,text"], }); This creates a new parser object that stores the event type and the original text in @array for text and comment events.

The following methods feed the HTML document to the "HTML::Parser"

object:

$p->parse( $string )

Parse $string as the next chunk of the HTML document. The return

value is normally a reference to the parser object (i.e. $p).

Handlers invoked should not attempt to modify the $string in-place

until $p->parse returns.

If an invoked event handler aborts parsing by calling $p->eof, then

$p->parse() will return a FALSE value.

$p->parse( $coderef )

If a code reference is passed as the argument to be parsed, then the chunks to be parsed are obtained by invoking this function repeatedly. Parsing continues until the function returns an empty

(or undefined) result. When this happens $p->eof is automatically

signaled.

Parsing will also abort if one of the event handlers calls $p->eof.

The effect of this is the same as: while (1) {

my $chunk = &$coderef();

if (!defined($chunk) || !length($chunk)) {

$p->eof;

return $p;

}

$p->parse($chunk) || return undef;

} But it is more efficient as this loop runs internally in XS code.

$p->parsefile( $file )

Parse text directly from a file. The $file argument can be a

filename, an open file handle, or a reference to an open file handle.

If $file contains a filename and the file can't be opened, then the

method returns an undefined value and $! tells why it failed.

Otherwise the return value is a reference to the parser object.

If a file handle is passed as the $file argument, then the file

will normally be read until EOF, but not closed.

If an invoked event handler aborts parsing by calling $p->eof, then

$p->parsefile() may not have read the entire file.

On systems with multi-byte line terminators, the values passed for

the offset and length argspecs may be too low if parsefile() is called on a file handle that is not in binary mode. If a filename is passed in, then parsefile() will open the file in binary mode.

$p->eof

Signals the end of the HTML document. Calling the $p->eof method

outside a handler callback will flush any remaining buffered text (which triggers the "text" event if there is any remaining text).

Calling $p->eof inside a handler will terminate parsing at that

point and cause $p->parse to return a FALSE value. This also

terminates parsing by $p->parsefile().

After $p->eof has been called, the parse() and parsefile() methods

can be invoked to feed new documents with the parser object. The return value from eof() is a reference to the parser object. Most parser options are controlled by boolean attributes. Each boolean attribute is enabled by calling the corresponding method with a TRUE argument and disabled with a FALSE argument. The attribute value is left unchanged if no argument is given. The return value from each method is the old attribute value. Methods that can be used to get and/or set parser options are:

$p->attrencoded

$p->attrencoded( $bool )

By default, the "attr" and @attr argspecs will have general entities for attribute values decoded. Enabling this attribute leaves entities alone.

$p->booleanattributevalue( $val )

This method sets the value reported for boolean attributes inside HTML start tags. By default, the name of the attribute is also used as its value. This affects the values reported for "tokens" and "attr" argspecs.

$p->casesensitive

$p->casesensitive( $bool )

By default, tagnames and attribute names are down-cased. Enabling

this attribute leaves them as found in the HTML source document.

$p->closingplaintext

$p->closingplaintext( $bool )

By default, "plaintext" element can never be closed. Everything up to the end of the document is parsed in CDATA mode. This historical behaviour is what at least MSIE does. Enabling this attribute makes closing "" tag effective and the parsing process will resume after seeing this tag. This emulates

gecko-based browsers.

$p->emptyelementtags

$p->emptyelementtags( $bool )

By default, empty element tags are not recognized as such and the "/" before ">" is just treated like a normal name character (unless "strictnames" is enabled). Enabling this attribute make

"HTML::Parser" recognize these tags.

Empty element tags look like start tags, but end with the character

sequence "/>" instead of ">". When recognized by "HTML::Parser"

they cause an artificial end event in addition to the start event. The "text" for the artificial end event will be empty and the "tokenpos" array will be undefined even though the the token array will have one element containing the tag name.

$p->markedsections

$p->markedsections( $bool )

By default, section markings like are treated like ordinary text. When this attribute is enabled section markings are honoured. There are currently no events associated with the marked section markup, but the text can be returned as "skippedtext".

$p->strictcomment

$p->strictcomment( $bool )

By default, comments are terminated by the first occurrence of

"->". This is the behaviour of most popular browsers (like

Mozilla, Opera and MSIE), but it is not correct according to the official HTML standard. Officially, you need an even number of

"-" tokens before the closing ">" is recognized and there may not

be anything but whitespace between an even and an odd "-".

The official behaviour is enabled by enabling this attribute. Enabling of 'strictcomment' also disables recognizing these forms as comments:

$p->strictend

$p->strictend( $bool )

By default, attributes and other junk are allowed to be present on end tags in a manner that emulates MSIE's behaviour. The official behaviour is enabled with this attribute. If enabled, only whitespace is allowed between the tagname and the final ">".

$p->strictnames

$p->strictnames( $bool )

By default, almost anything is allowed in tag and attribute names. This is the behaviour of most popular browsers and allows us to parse some broken tags with invalid attribute values like: [PREV

By default, "LIST]" is parsed as a boolean attribute, not as part of the ALT value as was clearly intended. This is also what Mozilla sees. The official behaviour is enabled by enabling this attribute. If enabled, it will cause the tag above to be reported as text since "LIST]" is not a legal attribute name.

$p->unbrokentext

$p->unbrokentext( $bool )

By default, blocks of text are given to the text handler as soon as possible (but the parser takes care always to break text at a

boundary between whitespace and non-whitespace so single words and

entities can always be decoded safely). This might create breaks that make it hard to do transformations on the text. When this attribute is enabled, blocks of text are always reported in one

piece. This will delay the text event until the following (non-

text) event has been recognized by the parser. Note that the "offset" argspec will give you the offset of the first segment of text and "length" is the combined length of the segments. Since there might be ignored tags in between, these numbers can't be used to directly index in the original document file.

$p->utf8mode

$p->utf8mode( $bool )

Enable this option when parsing raw undecoded UTF-8. This tells

the parser that the entities expanded for strings reported by

"attr", @attr and "dtext" should be expanded as decoded UTF-8 so

they end up compatible with the surrounding text. If "utf8mode" is enabled then it is an error to pass strings containing characters with code above 255 to the parse() method, and the parse() method will croak if you try. Example: The Unicode character "\x{2665}" is "\xE2\x99\xA5" when

UTF-8 encoded. The character can also be represented by the entity

"♥" or "♥". If we feed the parser:

$p->parse("\xE2\x99\xA5♥");

then "dtext" will be reported as "\xE2\x99\xA5\x{2665}" without "utf8mode" enabled, but as "\xE2\x99\xA5\xE2\x99\xA5" when enabled. The later string is what you want.

This option is only available with perl-5.8 or better.

$p->xmlmode

$p->xmlmode( $bool )

Enabling this attribute changes the parser to allow some XML constructs. This enables the behaviour controlled by individually by the "casesensitive", "emptyelementtags", "strictnames" and "xmlpic" attributes and also suppresses special treatment of elements that are parsed as CDATA for HTML.

$p->xmlpic

$p->xmlpic( $bool )

By default, processing instructions are terminated by ">". When this attribute is enabled, processing instructions are terminated by "?>" instead. As markup and text is recognized, handlers are invoked. The following method is used to set up handlers for different events:

$p->handler( event => \&subroutine, $argspec )

$p->handler( event => $methodname, $argspec )

$p->handler( event => \@accum, $argspec )

$p->handler( event => "" );

$p->handler( event => undef );

$p->handler( event );

This method assigns a subroutine, method, or array to handle an event. Event is one of "text", "start", "end", "declaration", "comment", "process", "startdocument", "enddocument" or "default". The "\&subroutine" is a reference to a subroutine which is called to handle the event.

The $methodname is the name of a method of $p which is called to

handle the event.

The @accum is an array that will hold the event information as sub-

arrays. If the second argument is "", the event is ignored. If it is undef, the default handler is invoked for the event.

The $argspec is a string that describes the information to be

reported for the event. Any requested information that does not apply to a specific event is passed as "undef". If argspec is omitted, then it is left unchanged.

The return value from $p->handler is the old callback routine or a

reference to the accumulator array. Any return values from handler callback routines/methods are always ignored. A handler callback can request parsing to be aborted by

invoking the $p->eof method. A handler callback is not allowed to

invoke the $p->parse() or $p->parsefile() method. An exception

will be raised if it tries. Examples:

$p->handler(start => "start", 'self, attr, attrseq, text' );

This causes the "start" method of object $p to be called for

'start' events. The callback signature is $p->start(\%attr,

\@attrseq, $text).

$p->handler(start => \&start, 'attr, attrseq, text' );

This causes subroutine start() to be called for 'start' events.

The callback signature is start(\%attr, \@attrseq, $text).

$p->handler(start => \@accum, '"S", attr, attrseq, text' );

This causes 'start' event information to be saved in @accum. The

array elements will be ['S', \%attr, \@attrseq, $text].

$p->handler(start => "");

This causes 'start' events to be ignored. It also suppresses invocations of any default handler for start events. It is in most

cases equivalent to $p->handler(start => sub {}), but is more

efficient. It is different from the empty-sub-handler in that

"skippedtext" is not reset by it.

$p->handler(start => undef);

This causes no handler to be associated with start events. If there is a default handler it will be invoked. Filters based on tags can be set up to limit the number of events reported. The main bottleneck during parsing is often the huge number of callbacks made from the parser. Applying filters can improve performance significantly. The following methods control filters:

$p->ignoreelements( @tags )

Both the "start" event and the "end" event as well as any events that would be reported in between are suppressed. The ignored elements can contain nested occurrences of itself. Example:

$p->ignoreelements(qw(script style));

The "script" and "style" tags will always nest properly since their content is parsed in CDATA mode. For most other tags "ignoreelements" must be used with caution since HTML is often not well formed.

$p->ignoretags( @tags )

Any "start" and "end" events involving any of the tags given are suppressed. To reset the filter (i.e. don't suppress any "start" and "end" events), call "ignoretags" without an argument.

$p->reporttags( @tags )

Any "start" and "end" events involving any of the tags not given are suppressed. To reset the filter (i.e. report all "start" and "end" events), call "reporttags" without an argument. Internally, the system has two filter lists, one for "reporttags" and one for "ignoretags", and both filters are applied. This effectively gives "ignoretags" precedence over "reporttags". Examples:

$p->ignoretags(qw(style));

$p->reporttags(qw(script style));

results in only "script" events being reported. AArrggssppeecc

Argspec is a string containing a comma-separated list that describes

the information reported by the event. The following argspec identifier names can be used: "attr" Attr causes a reference to a hash of attribute name/value pairs to be passed. Boolean attributes' values are either the value set by

$p->booleanattributevalue, or the attribute name if no value has

been set by $p->booleanattributevalue.

This passes undef except for "start" events. Unless "xmlmode" or "casesensitive" is enabled, the attribute names are forced to lower case. General entities are decoded in the attribute values and one layer of matching quotes enclosing the attribute values is removed. The Unicode character set is assumed for entity decoding. With

Perl version 5.6 or earlier only the Latin-1 range is supported,

and entities for characters outside the range 0..255 are left unchanged. @attr Basically the same as "attr", but keys and values are passed as individual arguments and the original sequence of the attributes is kept. The parameters passed will be the same as the @attr calculated here:

@attr = map { $ => $attr->{$} } @$attrseq;

assuming $attr and $attrseq here are the hash and array passed as

the result of "attr" and "attrseq" argspecs. This passes no values for events besides "start". "attrseq" Attrseq causes a reference to an array of attribute names to be passed. This can be useful if you want to walk the "attr" hash in the original sequence. This passes undef except for "start" events. Unless "xmlmode" or "casesensitive" is enabled, the attribute names are forced to lower case. "column" Column causes the column number of the start of the event to be passed. The first column on a line is 0. "dtext" Dtext causes the decoded text to be passed. General entities are automatically decoded unless the event was inside a CDATA section or was between literal start and end tags ("script", "style", "xmp", and "plaintext"). The Unicode character set is assumed for entity decoding. With

Perl version 5.6 or earlier only the Latin-1 range is supported,

and entities for characters outside the range 0..255 are left unchanged. This passes undef except for "text" events. "event" Event causes the event name to be passed. The event name is one of "text", "start", "end", "declaration", "comment", "process", "startdocument" or "enddocument". "iscdata" Iscdata causes a TRUE value to be passed if the event is inside a CDATA section or between literal start and end tags ("script", "style", "xmp", and "plaintext"). if the flag is FALSE for a text event, then you should normally either use "dtext" or decode the entities yourself before the text is processed further. "length" Length causes the number of bytes of the source text of the event to be passed. "line" Line causes the line number of the start of the event to be passed. The first line in the document is 1. Line counting doesn't start until at least one handler requests this value to be reported. "offset" Offset causes the byte position in the HTML document of the start of the event to be passed. The first byte in the document has offset 0. "offsetend" Offsetend causes the byte position in the HTML document of the end of the event to be passed. This is the same as "offset" + "length". "self" Self causes the current object to be passed to the handler. If the handler is a method, this must be the first element in the argspec. An alternative to passing self as an argspec is to register

closures that capture $self by themselves as handlers.

Unfortunately this creates circular references which prevent the

HTML::Parser object from being garbage collected. Using the "self"

argspec avoids this problem. "skippedtext" Skippedtext returns the concatenated text of all the events that have been skipped since the last time an event was reported. Events might be skipped because no handler is registered for them or because some filter applies. Skipped text also includes marked section markup, since there are no events that can catch it.

If an ""-handler is registered for an event, then the text for this

event is not included in "skippedtext". Skipped text both before

and after the ""-event is included in the next reported

"skippedtext". "tag" Same as "tagname", but prefixed with "/" if it belongs to an "end" event and "!" for a declaration. The "tag" does not have any prefix for "start" events, and is in this case identical to "tagname". "tagname" This is the element name (or generic identifier in SGML jargon) for start and end tags. Since HTML is case insensitive, this name is forced to lower case to ease string matching. Since XML is case sensitive, the tagname case is not changed when "xmlmode" is enabled. The same happens if the "casesensitive" attribute is set. The declaration type of declaration elements is also passed as a tagname, even if that is a bit strange. In fact, in the current implementation tagname is identical to "token0" except that the name may be forced to lower case. "token0" Token0 causes the original text of the first token string to be

passed. This should always be the same as $tokens->[0].

For "declaration" events, this is the declaration type. For "start" and "end" events, this is the tag name.

For "process" and non-strict "comment" events, this is everything

inside the tag. This passes undef if there are no tokens in the event. "tokenpos" Tokenpos causes a reference to an array of token positions to be passed. For each string that appears in "tokens", this array contains two numbers. The first number is the offset of the start of the token in the original "text" and the second number is the length of the token. Boolean attributes in a "start" event will have (0,0) for the attribute value offset and length. This passes undef if there are no tokens in the event (e.g., "text") and for artificial "end" events triggered by empty element tags. If you are using these offsets and lengths to modify "text", you should either work from right to left, or be very careful to calculate the changes to the offsets. "tokens" Tokens causes a reference to an array of token strings to be passed. The strings are exactly as they were found in the original text, no decoding or case changes are applied. For "declaration" events, the array contains each word, comment, and delimited string starting with the declaration type.

For "comment" events, this contains each sub-comment. If

$p->strictcomments is disabled, there will be only one sub-

comment. For "start" events, this contains the original tag name followed by the attribute name/value pairs. The values of boolean attributes

will be either the value set by $p->booleanattributevalue, or the

attribute name if no value has been set by

$p->booleanattributevalue.

For "end" events, this contains the original tag name (always one token). For "process" events, this contains the process instructions (always one token). This passes "undef" for "text" events. "text" Text causes the source text (including markup element delimiters) to be passed. "undef" Pass an undefined value. Useful as padding where the same handler routine is registered for multiple events. '...' A literal string of 0 to 255 characters enclosed in single (') or double (") quotes is passed as entered. The whole argspec string can be wrapped up in '@{...}' to signal that the resulting event array should be flattened. This only makes a difference if an array reference is used as the handler target. Consider this example:

$p->handler(text => [], 'text');

$p->handler(text => [], '@{text}']);

With two text events; "foo", "bar"; then the first example will end up with [["foo"], ["bar"]] and the second with ["foo", "bar"] in the handler target array. EEvveennttss Handlers for the following events can be registered: "comment" This event is triggered when a markup comment is recognized. Example:

"declaration" This event is triggered when a markup declaration is recognized. For typical HTML documents, the only declaration you are likely to find is . Example:

"http://www.w3.org/TR/html40/strict.dtd">

DTDs inside will confuse HTML::Parser.

"default" This event is triggered for events that do not have a specific handler. You can set up a handler for this event to catch stuff you did not want to catch explicitly. "end" This event is triggered when an end tag is recognized. Example: "enddocument"

This event is triggered when $p->eof is called and after any

remaining text is flushed. There is no document text associated with this event. "process" This event is triggered when a processing instructions markup is recognized. The format and content of processing instructions are system and application dependent. Examples: "start" This event is triggered when a start tag is recognized. Example: "startdocument" This event is triggered before any other events for a new document. A handler for it can be used to initialize stuff. There is no document text associated with this event. "text" This event is triggered when plain text (characters) is recognized. The text may contain multiple lines. A sequence of text may be

broken between several text events unless $p->unbrokentext is

enabled. The parser will make sure that it does not break a word or a sequence of whitespace between two text events. UUnniiccooddee