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IO::HTML(3)	      User Contributed Perl Documentation	   IO::HTML(3)

NAME
       IO::HTML	- Open an HTML file with automatic charset detection

VERSION
       This document describes version 1.001 of	IO::HTML, released June	28,
       2014.

SYNOPSIS
	 use IO::HTML;		       # exports html_file by default
	 use HTML::TreeBuilder;

	 my $tree = HTML::TreeBuilder->new_from_file(
		      html_file('foo.html')
		    );

	 # Alternative interface:
	 open(my $in, '<:raw', 'bar.html');
	 my $encoding =	IO::HTML::sniff_encoding($in, 'bar.html');

DESCRIPTION
       IO::HTML	provides an easy way to	open a file containing HTML while
       automatically determining its encoding.	It uses	the HTML5 encoding
       sniffing	algorithm specified in section 8.2.2.2 of the draft standard.

       The algorithm as	implemented here is:

       1.  If the file begins with a byte order	mark indicating	UTF-16LE,
	   UTF-16BE, or	UTF-8, then that is the	encoding.

       2.  If the first	1024 bytes of the file contain a "<meta>" tag that
	   indicates the charset, and Encode recognizes	the specified charset
	   name, then that is the encoding.  (This portion of the algorithm is
	   implemented by "find_charset_in".)

	   The "<meta>"	tag can	be in one of two formats:

	     <meta charset="...">
	     <meta http-equiv="Content-Type" content="...charset=...">

	   The search is case-insensitive, and the order of attributes within
	   the tag is irrelevant.  Any additional attributes of	the tag	are
	   ignored.  The first matching	tag with a recognized encoding ends
	   the search.

       3.  If the first	1024 bytes of the file are valid UTF-8 (with at	least
	   1 non-ASCII character), then	the encoding is	UTF-8.

       4.  If all else fails, use the default character	encoding.  The HTML5
	   standard suggests the default encoding should be locale dependent,
	   but currently it is always "cp1252" unless you set
	   $IO::HTML::default_encoding to a different value.  Note:
	   "sniff_encoding" does not apply this	step; only "html_file" does
	   that.

SUBROUTINES
   html_file
	 $filehandle = html_file($filename, \%options);

       This function (exported by default) is the primary entry	point.	It
       opens the file specified	by $filename for reading, uses
       "sniff_encoding"	to find	a suitable encoding layer, and applies it.  It
       also applies the	":crlf"	layer.	If the file begins with	a BOM, the
       filehandle is positioned	just after the BOM.

       The optional second argument is a hashref containing options.  The
       possible	keys are described under "find_charset_in".

       If "sniff_encoding" is unable to	determine the encoding,	it defaults to
       $IO::HTML::default_encoding, which is set to "cp1252" (a.k.a.
       Windows-1252) by	default.  According to the standard, the default
       should be locale	dependent, but that is not currently implemented.

       It dies if the file cannot be opened.

   html_file_and_encoding
	 ($filehandle, $encoding, $bom)
	   = html_file_and_encoding($filename, \%options);

       This function (exported only by request)	is just	like "html_file", but
       returns more information.  In addition to the filehandle, it returns
       the name	of the encoding	used, and a flag indicating whether a byte
       order mark was found (if	$bom is	true, the file began with a BOM).
       This may	be useful if you want to write the file	out again (especially
       in conjunction with the "html_outfile" function).

       The optional second argument is a hashref containing options.  The
       possible	keys are described under "find_charset_in".

       It dies if the file cannot be opened.  The result of calling it in
       scalar context is undefined.

   html_outfile
	 $filehandle = html_outfile($filename, $encoding, $bom);

       This function (exported only by request)	opens $filename	for output
       using $encoding,	and writes a BOM to it if $bom is true.	 If $encoding
       is "undef", it defaults to $IO::HTML::default_encoding.	$encoding may
       be either an encoding name or an	Encode::Encoding object.

       It dies if the file cannot be opened.

   sniff_encoding
	 ($encoding, $bom) = sniff_encoding($filehandle, $filename, \%options);

       This function (exported only by request)	runs the HTML5 encoding
       sniffing	algorithm on $filehandle (which	must be	seekable, and should
       have been opened	in ":raw" mode).  $filename is used only for error
       messages	(if there's a problem using the	filehandle), and defaults to
       "file" if omitted.  The optional	third argument is a hashref containing
       options.	 The possible keys are described under "find_charset_in".

       It returns Perl's canonical name	for the	encoding, which	is not
       necessarily the same as the MIME	or IANA	charset	name.  It returns
       "undef" if the encoding cannot be determined.  $bom is true if the file
       began with a byte order mark.  In scalar	context, it returns only
       $encoding.

       The filehandle's	position is restored to	its original position
       (normally the beginning of the file) unless $bom	is true.  In that
       case, the position is immediately after the BOM.

       Tip: If you want	to run "sniff_encoding"	on a file you've already
       loaded into a string, open an in-memory file on the string, and pass
       that handle:

	 ($encoding, $bom) = do	{
	   open(my $fh,	'<', \$string);	 sniff_encoding($fh)
	 };

       (This only makes	sense if $string contains bytes, not characters.)

   find_charset_in
	 $encoding = find_charset_in($string_containing_HTML, \%options);

       This function (exported only by request)	looks for charset information
       in a "<meta>" tag in a possibly incomplete HTML document	using the "two
       step" algorithm specified by HTML5.  It does not	look for a BOM.	 Only
       the first 1024 bytes of the string are checked.

       It returns Perl's canonical name	for the	encoding, which	is not
       necessarily the same as the MIME	or IANA	charset	name.  It returns
       "undef" if no charset is	specified or if	the specified charset is not
       recognized by the Encode	module.

       The optional second argument is a hashref containing options.  The
       following keys are recognized:

       "encoding"
	   If true, return the Encode::Encoding	object instead of its name.
	   Defaults to false.

       "need_pragma"
	   If true (the	default), follow the HTML5 spec	and examine the
	   "content" attribute only of "<meta http-equiv="Content-Type"".  If
	   set to 0, relax the HTML5 spec, and look for	"charset=" in the
	   "content" attribute of every	meta tag.

EXPORTS
       By default, only	"html_file" is exported.  Other	functions may be
       exported	on request.

       For people who prefer not to export functions, all functions beginning
       with "html_" have an alias without that prefix (e.g. you	can call
       "IO::HTML::file(...)" instead of	"IO::HTML::html_file(...)".  These
       aliases are not exportable.

       The following export tags are available:

       ":all"
	   All exportable functions.

       ":rw"
	   "html_file",	"html_file_and_encoding", "html_outfile".

SEE ALSO
       The HTML5 specification,	section	8.2.2.2	Determining the	character
       encoding:
       <http://www.w3.org/TR/html5/syntax.html#determining-the-character-encoding>

DIAGNOSTICS
       "Could not read %s: %s"
	   The specified file could not	be read	from for the reason specified
	   by $!.

       "Could not seek %s: %s"
	   The specified file could not	be rewound for the reason specified by
	   $!.

       "Failed to open %s: %s"
	   The specified file could not	be opened for reading for the reason
	   specified by	$!.

       "No default encoding specified"
	   The "sniff_encoding"	algorithm didn't find an encoding to use, and
	   you set $IO::HTML::default_encoding to "undef".

CONFIGURATION AND ENVIRONMENT
       IO::HTML	requires no configuration files	or environment variables.

DEPENDENCIES
       IO::HTML	has no non-core	dependencies for Perl 5.8.7+.  With earlier
       versions	of Perl	5.8, you need to upgrade Encode	to at least version
       2.10, and you may need to upgrade Exporter to at	least version 5.57.

INCOMPATIBILITIES
       None reported.

BUGS AND LIMITATIONS
       No bugs have been reported.

AUTHOR
       Christopher J. Madsen  "<perlA ATA cjmweb.net>"

       Please report any bugs or feature requests to
       "<bug-IO-HTMLA ATA rt.cpan.org>"	or through the web interface at
       <http://rt.cpan.org/Public/Bug/Report.html?Queue=IO-HTML>.

       You can follow or contribute to IO-HTML's development at
       <https://github.com/madsen/io-html>.

COPYRIGHT AND LICENSE
       This software is	copyright (c) 2014 by Christopher J. Madsen.

       This is free software; you can redistribute it and/or modify it under
       the same	terms as the Perl 5 programming	language system	itself.

DISCLAIMER OF WARRANTY
       BECAUSE THIS SOFTWARE IS	LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
       FOR THE SOFTWARE, TO THE	EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT
       WHEN OTHERWISE STATED IN	WRITING	THE COPYRIGHT HOLDERS AND/OR OTHER
       PARTIES PROVIDE THE SOFTWARE "AS	IS" WITHOUT WARRANTY OF	ANY KIND,
       EITHER EXPRESSED	OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
       WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
       ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF	THE SOFTWARE IS	WITH
       YOU. SHOULD THE SOFTWARE	PROVE DEFECTIVE, YOU ASSUME THE	COST OF	ALL
       NECESSARY SERVICING, REPAIR, OR CORRECTION.

       IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR	AGREED TO IN WRITING
       WILL ANY	COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
       REDISTRIBUTE THE	SOFTWARE AS PERMITTED BY THE ABOVE LICENSE, BE LIABLE
       TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
       CONSEQUENTIAL DAMAGES ARISING OUT OF THE	USE OR INABILITY TO USE	THE
       SOFTWARE	(INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
       RENDERED	INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
       FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
       SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
       DAMAGES.

perl v5.32.0			  2014-06-28			   IO::HTML(3)

NAME | VERSION | SYNOPSIS | DESCRIPTION | SUBROUTINES | EXPORTS | SEE ALSO | DIAGNOSTICS | CONFIGURATION AND ENVIRONMENT | DEPENDENCIES | INCOMPATIBILITIES | BUGS AND LIMITATIONS | AUTHOR | COPYRIGHT AND LICENSE | DISCLAIMER OF WARRANTY

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