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Encode(3)	       Perl Programmers	Reference Guide		     Encode(3)

       Encode -	character encodings in Perl

	   use Encode qw(decode	encode);
	   $characters = decode('UTF-8', $octets,     Encode::FB_CROAK);
	   $octets     = encode('UTF-8', $characters, Encode::FB_CROAK);

   Table of Contents
       Encode consists of a collection of modules whose	details	are too
       extensive to fit	in one document.  This one itself explains the top-
       level APIs and general topics at	a glance.  For other topics and	more
       details,	see the	documentation for these	modules:

       Encode::Alias - Alias definitions to encodings
       Encode::Encoding	- Encode Implementation	Base Class
       Encode::Supported - List	of Supported Encodings
       Encode::CN - Simplified Chinese Encodings
       Encode::JP - Japanese Encodings
       Encode::KR - Korean Encodings
       Encode::TW - Traditional	Chinese	Encodings

       The "Encode" module provides the	interface between Perl strings and the
       rest of the system.  Perl strings are sequences of characters.

       The repertoire of characters that Perl can represent is a superset of
       those defined by	the Unicode Consortium.	On most	platforms the ordinal
       values of a character as	returned by "ord(S)" is	the Unicode codepoint
       for that	character. The exceptions are platforms	where the legacy
       encoding	is some	variant	of EBCDIC rather than a	superset of ASCII; see

       During recent history, data is moved around a computer in 8-bit chunks,
       often called "bytes" but	also known as "octets" in standards documents.
       Perl is widely used to manipulate data of many types: not only strings
       of characters representing human	or computer languages, but also
       "binary"	data, being the	machine's representation of numbers, pixels in
       an image, or just about anything.

       When Perl is processing "binary data", the programmer wants Perl	to
       process "sequences of bytes". This is not a problem for Perl: because a
       byte has	256 possible values, it	easily fits in Perl's much larger
       "logical	character".

       This document mostly explains the how. perlunitut and perlunifaq
       explain the why.


       A character in the range	0 .. 2**32-1 (or more);	what Perl's strings
       are made	of.


       A character in the range	0..255;	a special case of a Perl character.


       8 bits of data, with ordinal values 0..255; term	for bytes passed to or
       from a non-Perl context,	such as	a disk file, standard I/O stream,
       database, command-line argument,	environment variable, socket etc.

   Basic methods

	 $octets  = encode(ENCODING, STRING[, CHECK])

       Encodes the scalar value	STRING from Perl's internal form into ENCODING
       and returns a sequence of octets.  ENCODING can be either a canonical
       name or an alias.  For encoding names and aliases, see "Defining
       Aliases".  For CHECK, see "Handling Malformed Data".

       CAVEAT: the input scalar	STRING might be	modified in-place depending on
       what is set in CHECK. See "LEAVE_SRC" if	you want your inputs to	be
       left unchanged.

       For example, to convert a string	from Perl's internal format into
       ISO-8859-1, also	known as Latin1:

	 $octets = encode("iso-8859-1",	$string);

       CAVEAT: When you	run "$octets = encode("UTF-8", $string)", then $octets
       might not be equal to $string.  Though both contain the same data, the
       UTF8 flag for $octets is	always off.  When you encode anything, the
       UTF8 flag on the	result is always off, even when	it contains a
       completely valid	UTF-8 string. See "The UTF8 flag" below.

       If the $string is "undef", then "undef" is returned.

       "str2bytes" may be used as an alias for "encode".


	 $string = decode(ENCODING, OCTETS[, CHECK])

       This function returns the string	that results from decoding the scalar
       value OCTETS, assumed to	be a sequence of octets	in ENCODING, into
       Perl's internal form.  As with encode(),	ENCODING can be	either a
       canonical name or an alias. For encoding	names and aliases, see
       "Defining Aliases"; for CHECK, see "Handling Malformed Data".

       CAVEAT: the input scalar	OCTETS might be	modified in-place depending on
       what is set in CHECK. See "LEAVE_SRC" if	you want your inputs to	be
       left unchanged.

       For example, to convert ISO-8859-1 data into a string in	Perl's
       internal	format:

	 $string = decode("iso-8859-1",	$octets);

       CAVEAT: When you	run "$string = decode("UTF-8", $octets)", then $string
       might not be equal to $octets.  Though both contain the same data, the
       UTF8 flag for $string is	on.  See "The UTF8 flag" below.

       If the $string is "undef", then "undef" is returned.

       "bytes2str" may be used as an alias for "decode".


	 [$obj =] find_encoding(ENCODING)

       Returns the encoding object corresponding to ENCODING.  Returns "undef"
       if no matching ENCODING is find.	 The returned object is	what does the
       actual encoding or decoding.

	 $string = decode($name, $bytes);

       is in fact

	   $string = do	{
	       $obj = find_encoding($name);
	       croak qq(encoding "$name" not found) unless ref $obj;

       with more error checking.

       You can therefore save time by reusing this object as follows;

	   my $enc = find_encoding("iso-8859-1");
	   while(<>) {
	       my $string = $enc->decode($_);
	       ... # now do something with $string;

       Besides "decode"	and "encode", other methods are	available as well.
       For instance, "name()" returns the canonical name of the	encoding

	 find_encoding("latin1")->name;	# iso-8859-1

       See Encode::Encoding for	details.


	 [$obj =] find_mime_encoding(MIME_ENCODING)

       Returns the encoding object corresponding to MIME_ENCODING.  Acts same
       as "find_encoding()" but	"mime_name()" of returned object must match to
       MIME_ENCODING.  So as opposite of "find_encoding()" canonical names and
       aliases are not used when searching for object.

	   find_mime_encoding("utf8"); # returns undef because "utf8" is not valid I<MIME_ENCODING>
	   find_mime_encoding("utf-8");	# returns encode object	"utf-8-strict"
	   find_mime_encoding("UTF-8");	# same as "utf-8" because I<MIME_ENCODING> is case insensitive
	   find_mime_encoding("utf-8-strict"); returns undef because "utf-8-strict" is not valid I<MIME_ENCODING>


	 [$length =] from_to($octets, FROM_ENC,	TO_ENC [, CHECK])

       Converts	in-place data between two encodings. The data in $octets must
       be encoded as octets and	not as characters in Perl's internal format.
       For example, to convert ISO-8859-1 data into Microsoft's	CP1250

	 from_to($octets, "iso-8859-1",	"cp1250");

       and to convert it back:

	 from_to($octets, "cp1250", "iso-8859-1");

       Because the conversion happens in place,	the data to be converted
       cannot be a string constant: it must be a scalar	variable.

       "from_to()" returns the length of the converted string in octets	on
       success,	and "undef" on error.

       CAVEAT: The following operations	may look the same, but are not:

	 from_to($data,	"iso-8859-1", "UTF-8");	#1
	 $data = decode("iso-8859-1", $data);  #2

       Both #1 and #2 make $data consist of a completely valid UTF-8 string,
       but only	#2 turns the UTF8 flag on.  #1 is equivalent to:

	 $data = encode("UTF-8", decode("iso-8859-1", $data));

       See "The	UTF8 flag" below.

       Also note that:

	 from_to($octets, $from, $to, $check);

       is equivalent to:

	 $octets = encode($to, decode($from, $octets), $check);

       Yes, it does not	respect	the $check during decoding.  It	is
       deliberately done that way.  If you need	minute control,	use "decode"
       followed	by "encode" as follows:

	 $octets = encode($to, decode($from, $octets, $check_from), $check_to);


	 $octets = encode_utf8($string);

       Equivalent to "$octets =	encode("utf8", $string)".  The characters in
       $string are encoded in Perl's internal format, and the result is
       returned	as a sequence of octets.  Because all possible characters in
       Perl have a (loose, not strict) utf8 representation, this function
       cannot fail.

       WARNING:	do not use this	function for data exchange as it can produce
       not strict utf8 $octets!	For strictly valid UTF-8 output	use "$octets =
       encode("UTF-8", $string)".


	 $string = decode_utf8($octets [, CHECK]);

       Equivalent to "$string =	decode("utf8", $octets [, CHECK])".  The
       sequence	of octets represented by $octets is decoded from (loose, not
       strict) utf8 into a sequence of logical characters.  Because not	all
       sequences of octets are valid not strict	utf8, it is quite possible for
       this function to	fail.  For CHECK, see "Handling	Malformed Data".

       WARNING:	do not use this	function for data exchange as it can produce
       $string with not	strict utf8 representation! For	strictly valid UTF-8
       $string representation use "$string = decode("UTF-8", $octets [,

       CAVEAT: the input $octets might be modified in-place depending on what
       is set in CHECK.	See "LEAVE_SRC"	if you want your inputs	to be left

   Listing available encodings
	 use Encode;
	 @list = Encode->encodings();

       Returns a list of canonical names of available encodings	that have
       already been loaded.  To	get a list of all available encodings
       including those that have not yet been loaded, say:

	 @all_encodings	= Encode->encodings(":all");

       Or you can give the name	of a specific module:

	 @with_jp = Encode->encodings("Encode::JP");

       When ""::"" is not in the name, ""Encode::"" is assumed.

	 @ebcdic = Encode->encodings("EBCDIC");

       To find out in detail which encodings are supported by this package,
       see Encode::Supported.

   Defining Aliases
       To add a	new alias to a given encoding, use:

	 use Encode;
	 use Encode::Alias;
	 define_alias(NEWNAME => ENCODING);

       After that, NEWNAME can be used as an alias for ENCODING.  ENCODING may
       be either the name of an	encoding or an encoding	object.

       Before you do that, first make sure the alias is	nonexistent using
       "resolve_alias()", which	returns	the canonical name thereof.  For

	 Encode::resolve_alias("latin1") eq "iso-8859-1" # true
	 Encode::resolve_alias("iso-8859-12")	# false; nonexistent
	 Encode::resolve_alias($name) eq $name	# true if $name	is canonical

       "resolve_alias()" does not need "use Encode::Alias"; it can be imported
       via "use	Encode qw(resolve_alias)".

       See Encode::Alias for details.

   Finding IANA	Character Set Registry names
       The canonical name of a given encoding does not necessarily agree with
       IANA Character Set Registry, commonly seen as "Content-Type:
       text/plain; charset=WHATEVER".  For most	cases, the canonical name
       works, but sometimes it does not, most notably with "utf-8-strict".

       As of "Encode" version 2.21, a new method "mime_name()" is therefore

	 use Encode;
	 my $enc = find_encoding("UTF-8");
	 warn $enc->name;      # utf-8-strict
	 warn $enc->mime_name; # UTF-8

       See also:  Encode::Encoding

Encoding via PerlIO
       If your perl supports "PerlIO" (which is	the default), you can use a
       "PerlIO"	layer to decode	and encode directly via	a filehandle.  The
       following two examples are fully	identical in functionality:

	 ### Version 1 via PerlIO
	   open(INPUT,	"< :encoding(shiftjis)", $infile)
	       || die "Can't open < $infile for	reading: $!";
	   open(OUTPUT,	"> :encoding(euc-jp)",	$outfile)
	       || die "Can't open > $output for	writing: $!";
	   while (<INPUT>) {   # auto decodes $_
	       print OUTPUT;   # auto encodes $_
	   close(INPUT)	  || die "can't	close $infile: $!";
	   close(OUTPUT)  || die "can't	close $outfile:	$!";

	 ### Version 2 via from_to()
	   open(INPUT,	"< :raw", $infile)
	       || die "Can't open < $infile for	reading: $!";
	   open(OUTPUT,	"> :raw",  $outfile)
	       || die "Can't open > $output for	writing: $!";

	   while (<INPUT>) {
	       from_to($_, "shiftjis", "euc-jp", 1);  #	switch encoding
	       print OUTPUT;   # emit raw (but properly	encoded) data
	   close(INPUT)	  || die "can't	close $infile: $!";
	   close(OUTPUT)  || die "can't	close $outfile:	$!";

       In the first version above, you let the appropriate encoding layer
       handle the conversion.  In the second, you explicitly translate from
       one encoding to the other.

       Unfortunately, it may be	that encodings are not "PerlIO"-savvy.	You
       can check to see	whether	your encoding is supported by "PerlIO" by
       invoking	the "perlio_ok"	method on it:

	 Encode::perlio_ok("hz");	      #	false
	 find_encoding("euc-cn")->perlio_ok;  #	true wherever PerlIO is	available

	 use Encode qw(perlio_ok);	      #	imported upon request

       Fortunately, all	encodings that come with "Encode" core are
       "PerlIO"-savvy except for "hz" and "ISO-2022-kr".  For the gory
       details,	see Encode::Encoding and Encode::PerlIO.

Handling Malformed Data
       The optional CHECK argument tells "Encode" what to do when encountering
       malformed data.	Without	CHECK, "Encode::FB_DEFAULT" (==	0) is assumed.

       As of version 2.12, "Encode" supports coderef values for	"CHECK"; see

       NOTE: Not all encodings support this feature.  Some encodings ignore
       the CHECK argument.  For	example, Encode::Unicode ignores CHECK and it
       always croaks on	error.

   List	of CHECK values

	 I<CHECK> = Encode::FB_DEFAULT ( == 0)

       If CHECK	is 0, encoding and decoding replace any	malformed character
       with a substitution character.  When you	encode,	SUBCHAR	is used.  When
       you decode, the Unicode REPLACEMENT CHARACTER, code point U+FFFD, is
       used.  If the data is supposed to be UTF-8, an optional lexical warning
       of warning category "utf8" is given.


	 I<CHECK> = Encode::FB_CROAK ( == 1)

       If CHECK	is 1, methods immediately die with an error message.
       Therefore, when CHECK is	1, you should trap exceptions with "eval{}",
       unless you really want to let it	"die".


	 I<CHECK> = Encode::FB_QUIET

       If CHECK	is set to "Encode::FB_QUIET", encoding and decoding
       immediately return the portion of the data that has been	processed so
       far when	an error occurs. The data argument is overwritten with
       everything after	that point; that is, the unprocessed portion of	the
       data.  This is handy when you have to call "decode" repeatedly in the
       case where your source data may contain partial multi-byte character
       sequences, (that	is, you	are reading with a fixed-width buffer).	Here's
       some sample code	to do exactly that:

	   my($buffer, $string)	= ("", "");
	   while (read($fh, $buffer, 256, length($buffer))) {
	       $string .= decode($encoding, $buffer, Encode::FB_QUIET);
	       # $buffer now contains the unprocessed partial character


	 I<CHECK> = Encode::FB_WARN

       This is the same	as "FB_QUIET" above, except that instead of being
       silent on errors, it issues a warning.  This is handy for when you are


       perlqq mode (CHECK = Encode::FB_PERLQQ)
       HTML charref mode (CHECK	= Encode::FB_HTMLCREF)
       XML charref mode	(CHECK = Encode::FB_XMLCREF)

       For encodings that are implemented by the "Encode::XS" module, "CHECK"
       "==" "Encode::FB_PERLQQ"	puts "encode" and "decode" into	"perlqq"
       fallback	mode.

       When you	decode,	"\xHH" is inserted for a malformed character, where HH
       is the hex representation of the	octet that could not be	decoded	to
       utf8.  When you encode, "\x{HHHH}" will be inserted, where HHHH is the
       Unicode code point (in any number of hex	digits)	of the character that
       cannot be found in the character	repertoire of the encoding.

       The HTML/XML character reference	modes are about	the same. In place of
       "\x{HHHH}", HTML	uses "&#NNN;" where NNN	is a decimal number, and XML
       uses "&#xHHHH;" where HHHH is the hexadecimal number.

       In "Encode" 2.10	or later, "LEAVE_SRC" is also implied.

       The bitmask

       These modes are all actually set	via a bitmask.	Here is	how the
       "FB_XXX"	constants are laid out.	 You can import	the "FB_XXX" constants
       via "use	Encode qw(:fallbacks)",	and you	can import the generic bitmask
       constants via "use Encode qw(:fallback_all)".

	DIE_ON_ERR    0x0001		 X
	WARN_ON_ERR   0x0002				   X
	RETURN_ON_ERR 0x0004			  X	   X
	LEAVE_SRC     0x0008					    X
	PERLQQ	      0x0100					    X
	HTMLCREF      0x0200
	XMLCREF	      0x0400



       If the "Encode::LEAVE_SRC" bit is not set but CHECK is set, then	the
       source string to	encode() or decode() will be overwritten in place.  If
       you're not interested in	this, then bitwise-OR it with the bitmask.

   coderef for CHECK
       As of "Encode" 2.12, "CHECK" can	also be	a code reference which takes
       the ordinal value of the	unmapped character as an argument and returns
       octets that represent the fallback character.  For instance:

	 $ascii	= encode("ascii", $utf8, sub{ sprintf "<U+%04X>", shift	});

       Acts like "FB_PERLQQ" but U+XXXX	is used	instead	of "\x{XXXX}".

       Fallback	for "decode" must return decoded string	(sequence of
       characters) and takes a list of ordinal values as its arguments.	So for
       example if you wish to decode octets as UTF-8, and use ISO-8859-15 as a
       fallback	for bytes that are not valid UTF-8, you	could write

	   $str	= decode 'UTF-8', $octets, sub {
	       my $tmp = join '', map chr, @_;
	       return decode 'ISO-8859-15', $tmp;

Defining Encodings
       To define a new encoding, use:

	   use Encode qw(define_encoding);
	   define_encoding($object, CANONICAL_NAME [, alias...]);

       CANONICAL_NAME will be associated with $object.	The object should
       provide the interface described in Encode::Encoding.  If	more than two
       arguments are provided, additional arguments are	considered aliases for

       See Encode::Encoding for	details.

The UTF8 flag
       Before the introduction of Unicode support in Perl, The "eq" operator
       just compared the strings represented by	two scalars. Beginning with
       Perl 5.8, "eq" compares two strings with	simultaneous consideration of
       the UTF8	flag. To explain why we	made it	so, I quote from page 402 of
       Programming Perl, 3rd ed.

       Goal #1:
	 Old byte-oriented programs should not spontaneously break on the old
	 byte-oriented data they used to work on.

       Goal #2:
	 Old byte-oriented programs should magically start working on the new
	 character-oriented data when appropriate.

       Goal #3:
	 Programs should run just as fast in the new character-oriented	mode
	 as in the old byte-oriented mode.

       Goal #4:
	 Perl should remain one	language, rather than forking into a byte-
	 oriented Perl and a character-oriented	Perl.

       When Programming	Perl, 3rd ed. was written, not even Perl 5.6.0 had
       been born yet, many features documented in the book remained
       unimplemented for a long	time.  Perl 5.8	corrected much of this,	and
       the introduction	of the UTF8 flag is one	of them.  You can think	of
       there being two fundamentally different kinds of	strings	and string-
       operations in Perl: one a byte-oriented mode  for when the internal
       UTF8 flag is off, and the other a character-oriented mode for when the
       internal	UTF8 flag is on.

       This UTF8 flag is not visible in	Perl scripts, exactly for the same
       reason you cannot (or rather, you don't have to)	see whether a scalar
       contains	a string, an integer, or a floating-point number.   But	you
       can still peek and poke these if	you will.  See the next	section.

   Messing with	Perl's Internals
       The following API uses parts of Perl's internals	in the current
       implementation.	As such, they are efficient but	may change in a	future


	 is_utf8(STRING	[, CHECK])

       [INTERNAL] Tests	whether	the UTF8 flag is turned	on in the STRING.  If
       CHECK is	true, also checks whether STRING contains well-formed UTF-8.
       Returns true if successful, false otherwise.

       Typically only necessary	for debugging and testing.  Don't use this
       flag as a marker	to distinguish character and binary data, that should
       be decided for each variable when you write your	code.

       CAVEAT: If STRING has UTF8 flag set, it does NOT	mean that STRING is
       UTF-8 encoded and vice-versa.

       As of Perl 5.8.1, utf8 also has the "utf8::is_utf8" function.



       [INTERNAL] Turns	the STRING's internal UTF8 flag	on.  The STRING	is not
       checked for containing only well-formed UTF-8.  Do not use this unless
       you know	with absolute certainty	that the STRING	holds only well-formed
       UTF-8.  Returns the previous state of the UTF8 flag (so please don't
       treat the return	value as indicating success or failure), or "undef" if
       STRING is not a string.

       NOTE: For security reasons, this	function does not work on tainted



       [INTERNAL] Turns	the STRING's internal UTF8 flag	off.  Do not use
       frivolously.  Returns the previous state	of the UTF8 flag, or "undef"
       if STRING is not	a string.  Do not treat	the return value as indicative
       of success or failure, because that isn't what it means:	it is only the
       previous	setting.

       NOTE: For security reasons, this	function does not work on tainted

UTF-8 vs. utf8 vs. UTF8
	 ....We	now view strings not as	sequences of bytes, but	as sequences
	 of numbers in the range 0 .. 2**32-1 (or in the case of 64-bit
	 computers, 0 .. 2**64-1) -- Programming Perl, 3rd ed.

       That has	historically been Perl's notion	of UTF-8, as that is how UTF-8
       was first conceived by Ken Thompson when	he invented it.	However,
       thanks to later revisions to the	applicable standards, official UTF-8
       is now rather stricter than that. For example, its range	is much
       narrower	(0 .. 0x10_FFFF	to cover only 21 bits instead of 32 or 64
       bits) and some sequences	are not	allowed, like those used in surrogate
       pairs, the 31 non-character code	points 0xFDD0 .. 0xFDEF, the last two
       code points in any plane	(0xXX_FFFE and 0xXX_FFFF), all non-shortest
       encodings, etc.

       The former default in which Perl	would always use a loose
       interpretation of UTF-8 has now been overruled:

	 From: Larry Wall <>
	 Date: December	04, 2004 11:51:58 JST
	 Subject: Re: Make support the real UTF-8
	 Message-Id: <>

	 On Fri, Dec 03, 2004 at 10:12:12PM +0000, Tim Bunce wrote:
	 : I've	no problem with	'utf8' being perl's unrestricted uft8 encoding,
	 : but "UTF-8" is the name of the standard and should give the
	 : corresponding behaviour.

	 For what it's worth, that's how I've always kept them straight	in my

	 Also for what it's worth, Perl	6 will mostly default to strict	but
	 make it easy to switch	back to	lax.


       Got that?  As of	Perl 5.8.7, "UTF-8" means UTF-8	in its current sense,
       which is	conservative and strict	and security-conscious,	whereas	"utf8"
       means UTF-8 in its former sense,	which was liberal and loose and	lax.
       "Encode"	version	2.10 or	later thus groks this subtle but critically
       important distinction between "UTF-8" and "utf8".

	 encode("utf8",	 "\x{FFFF_FFFF}", 1); #	okay
	 encode("UTF-8", "\x{FFFF_FFFF}", 1); #	croaks

       In the "Encode" module, "UTF-8" is actually a canonical name for
       "utf-8-strict".	That hyphen between the	"UTF" and the "8" is critical;
       without it, "Encode" goes "liberal" and (perhaps	overly-)permissive:

	 find_encoding("UTF-8")->name #	is 'utf-8-strict'
	 find_encoding("utf-8")->name #	ditto. names are case insensitive
	 find_encoding("utf_8")->name #	ditto. "_" are treated as "-"
	 find_encoding("UTF8")->name  #	is 'utf8'.

       Perl's internal UTF8 flag is called "UTF8", without a hyphen. It
       indicates whether a string is internally	encoded	as "utf8", also
       without a hyphen.

       Encode::Encoding, Encode::Supported, Encode::PerlIO, encoding,
       perlebcdic, "open" in perlfunc, perlunicode, perluniintro, perlunifaq,
       perlunitut utf8,	the Perl Unicode Mailing List

       This project was	originated by the late Nick Ing-Simmons	and later
       maintained by Dan Kogai _dankogai@cpan.org_.  See AUTHORS for a full
       list of people involved.	 For any questions, send mail to
       _perl-unicode@perl.org_ so that we can all share.

       While Dan Kogai retains the copyright as	a maintainer, credit should go
       to all those involved.  See AUTHORS for a list of those who submitted
       code to the project.

       Copyright 2002-2014 Dan Kogai _dankogai@cpan.org_.

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

perl v5.28.3			  2020-05-14			     Encode(3)

NAME | SYNOPSIS | DESCRIPTION | THE PERL ENCODING API | Encoding via PerlIO | Handling Malformed Data | Defining Encodings | The UTF8 flag | UTF-8 vs. utf8 vs. UTF8 | SEE ALSO | MAINTAINER | COPYRIGHT

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