3 perluniintro - Perl Unicode introduction
7 This document gives a general idea of Unicode and how to use Unicode
12 Unicode is a character set standard with plans to cover all of the
13 writing systems of the world, plus many other symbols.
15 Unicode and ISO/IEC 10646 are coordinated standards that provide code
16 points for the characters in almost all modern character set standards,
17 covering more than 30 writing systems and hundreds of languages,
18 including all commercially important modern languages. All characters
19 in the largest Chinese, Japanese, and Korean dictionaries are also
20 encoded. The standards will eventually cover almost all characters in
21 more than 250 writing systems and thousands of languages.
23 A Unicode I<character> is an abstract entity. It is not bound to any
24 particular integer width, and especially not to the C language C<char>.
25 Unicode is language neutral and display neutral: it doesn't encode the
26 language of the text, and it doesn't define fonts or other graphical
27 layout details. Unicode operates on characters and on text built from
30 Unicode defines characters like C<LATIN CAPITAL LETTER A> or C<GREEK
31 SMALL LETTER ALPHA>, and then unique numbers for those, hexadecimal
32 0x0041 or 0x03B1 for those particular characters. Such unique
33 numbers are called I<code points>.
35 The Unicode standard prefers using hexadecimal notation for the code
36 points. (In case this notation, numbers like 0x0041, is unfamiliar to
37 you, take a peek at a later section, L</"Hexadecimal Notation">.)
38 The Unicode standard uses the notation C<U+0041 LATIN CAPITAL LETTER A>,
39 which gives the hexadecimal code point, and the normative name of
42 Unicode also defines various I<properties> for the characters, like
43 "uppercase" or "lowercase", "decimal digit", or "punctuation":
44 these properties are independent of the names of the characters.
45 Furthermore, various operations on the characters like uppercasing,
46 lowercasing, and collating (sorting), are defined.
48 A Unicode character consists either of a single code point, or a
49 I<base character> (like C<LATIN CAPITAL LETTER A>), followed by one or
50 more I<modifiers> (like C<COMBINING ACUTE ACCENT>). This sequence of
51 a base character and modifiers is called a I<combining character
54 Whether to call these combining character sequences, as a whole,
55 "characters" depends on your point of view. If you are a programmer,
56 you probably would tend towards seeing each element in the sequences
57 as one unit, one "character", but from the user viewpoint, the
58 sequence as a whole is probably considered one "character", since
59 that's probably what it looks like in the context of the user's
62 With this "as a whole" view of characters, the number of characters is
63 open-ended. But in the programmer's "one unit is one character" point
64 of view, the concept of "characters" is more deterministic, and so we
65 take that point of view in this document: one "character" is one
66 Unicode code point, be it a base character or a combining character.
68 For some of the combinations there are I<precomposed> characters,
69 for example C<LATIN CAPITAL LETTER A WITH ACUTE> is defined as
70 a single code point. These precomposed characters are, however,
71 often available only for some combinations, and mainly they are
72 meant to support round-trip conversions between Unicode and legacy
73 standards (like the ISO 8859), and in general case the composing
74 method is more extensible. To support conversion between the
75 different compositions of the characters, various I<normalization
76 forms> are also defined.
78 Because of backward compatibility with legacy encodings, the "a unique
79 number for every character" breaks down a bit: "at least one number
80 for every character" is closer to truth. (This happens when the same
81 character has been encoded in several legacy encodings.) The converse
82 is also not true: not every code point has an assigned character.
83 Firstly, there are unallocated code points within otherwise used
84 blocks. Secondly, there are special Unicode control characters that
85 do not represent true characters.
87 A common myth about Unicode is that it would be "16-bit", that is,
88 0x10000 (or 65536) characters from 0x0000 to 0xFFFF. B<This is untrue.>
89 Since Unicode 2.0 Unicode has been defined all the way up to 21 bits
90 (0x10FFFF), and since 3.1 characters have been defined beyond 0xFFFF.
91 The first 0x10000 characters are called the I<Plane 0>, or the I<Basic
92 Multilingual Plane> (BMP). With the Unicode 3.1, 17 planes in all are
93 defined (but nowhere near full of defined characters yet).
95 Another myth is that the 256-character blocks have something to do
96 with languages: a block per language. B<Also this is untrue.>
97 The division into the blocks exists but it is almost completely
98 accidental, an artifact of how the characters have been historically
99 allocated. Instead, there is a concept called I<scripts>, which may
100 be more useful: there is C<Latin> script, C<Greek> script, and so on.
101 Scripts usually span several parts of several blocks. For further
102 information see L<Unicode::UCD>.
104 The Unicode code points are just abstract numbers. To input and
105 output these abstract numbers, the numbers must be I<encoded> somehow.
106 Unicode defines several I<character encoding forms>, of which I<UTF-8>
107 is perhaps the most popular. UTF-8 is a variable length encoding that
108 encodes Unicode characters as 1 to 6 bytes (only 4 with the currently
109 defined characters). Other encodings include UTF-16 and UTF-32 and their
110 big and little endian variants (UTF-8 is byteorder independent).
111 The ISO/IEC 10646 defines the UCS-2 and UCS-4 encoding forms.
113 For more information about encodings, for example to learn what
114 I<surrogates> and I<byte order marks> (BOMs) are, see L<perlunicode>.
116 =head2 Perl's Unicode Support
118 Starting from Perl 5.6.0, Perl has had the capability of handling
119 Unicode natively. The first recommended release for serious Unicode
120 work is Perl 5.8.0, however. The maintenance release 5.6.1 fixed many
121 of the problems of the initial implementation of Unicode, but for
122 example regular expressions didn't really work with Unicode.
124 B<Starting from Perl 5.8.0, the use of C<use utf8> is no longer
125 necessary.> In earlier releases the C<utf8> pragma was used to declare
126 that operations in the current block or file would be Unicode-aware.
127 This model was found to be wrong, or at least clumsy: the Unicodeness
128 is now carried with the data, not attached to the operations. (There
129 is one remaining case where an explicit C<use utf8> is needed: if your
130 Perl script itself is encoded in UTF-8, you can use UTF-8 in your
131 identifier names, and in your string and regular expression literals,
132 by saying C<use utf8>. This is not the default because that would
133 break existing scripts having legacy 8-bit data in them.)
135 =head2 Perl's Unicode Model
137 Perl supports both the old, pre-5.6, model of strings of eight-bit
138 native bytes, and strings of Unicode characters. The principle is
139 that Perl tries to keep its data as eight-bit bytes for as long as
140 possible, but as soon as Unicodeness cannot be avoided, the data is
141 transparently upgraded to Unicode.
143 Internally, Perl currently uses either whatever the native eight-bit
144 character set of the platform (for example Latin-1) or UTF-8 to encode
145 Unicode strings. Specifically, if all code points in the string are
146 0xFF or less, Perl uses the native eight-bit character set.
147 Otherwise, it uses UTF-8.
149 A user of Perl does not normally need to know nor care how Perl
150 happens to encode its internal strings, but it becomes relevant when
151 outputting Unicode strings to a stream without a discipline (one with
152 the "default default"). In such a case, the raw bytes used internally
153 (the native character set or UTF-8, as appropriate for each string)
154 will be used, and a "Wide character" warning will be issued if those
155 strings contain a character beyond 0x00FF.
159 perl -e 'print "\x{DF}\n", "\x{0100}\x{DF}\n"'
161 produces a fairly useless mixture of native bytes and UTF-8, as well
164 To output UTF-8 always, use the ":utf8" output discipline. Prepending
166 binmode(STDOUT, ":utf8");
168 to this sample program ensures the output is completely UTF-8, and
169 of course, removes the warning.
171 If your locale environment variables (LANGUAGE, LC_ALL, LC_CTYPE, LANG)
172 contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching),
173 the default encoding of your STDIN, STDOUT, and STDERR, and of
174 B<any subsequent file open>, is UTF-8. Note that this means
175 that Perl expects other software to work, too: if STDIN coming
176 in from another command is not UTF-8, Perl will complain about
179 =head2 Unicode and EBCDIC
181 Perl 5.8.0 also supports Unicode on EBCDIC platforms. There,
182 the Unicode support is somewhat more complex to implement since
183 additional conversions are needed at every step. Some problems
184 remain, see L<perlebcdic> for details.
186 In any case, the Unicode support on EBCDIC platforms is better than
187 in the 5.6 series, which didn't work much at all for EBCDIC platform.
188 On EBCDIC platforms, the internal Unicode encoding form is UTF-EBCDIC
189 instead of UTF-8 (the difference is that as UTF-8 is "ASCII-safe" in
190 that ASCII characters encode to UTF-8 as-is, UTF-EBCDIC is
193 =head2 Creating Unicode
195 To create Unicode characters in literals for code points above 0xFF,
196 use the C<\x{...}> notation in doublequoted strings:
198 my $smiley = "\x{263a}";
200 Similarly in regular expression literals
202 $smiley =~ /\x{263a}/;
204 At run-time you can use C<chr()>:
206 my $hebrew_alef = chr(0x05d0);
208 (See L</"Further Resources"> for how to find all these numeric codes.)
210 Naturally, C<ord()> will do the reverse: turn a character to a code point.
212 Note that C<\x..> (no C<{}> and only two hexadecimal digits),
213 C<\x{...}>, and C<chr(...)> for arguments less than 0x100 (decimal
214 256) generate an eight-bit character for backward compatibility with
215 older Perls. For arguments of 0x100 or more, Unicode characters are
216 always produced. If you want to force the production of Unicode
217 characters regardless of the numeric value, use C<pack("U", ...)>
218 instead of C<\x..>, C<\x{...}>, or C<chr()>.
220 You can also use the C<charnames> pragma to invoke characters
221 by name in doublequoted strings:
223 use charnames ':full';
224 my $arabic_alef = "\N{ARABIC LETTER ALEF}";
226 And, as mentioned above, you can also C<pack()> numbers into Unicode
229 my $georgian_an = pack("U", 0x10a0);
231 Note that both C<\x{...}> and C<\N{...}> are compile-time string
232 constants: you cannot use variables in them. if you want similar
233 run-time functionality, use C<chr()> and C<charnames::vianame()>.
235 Also note that if all the code points for pack "U" are below 0x100,
236 bytes will be generated, just like if you were using C<chr()>.
238 my $bytes = pack("U*", 0x80, 0xFF);
240 If you want to force the result to Unicode characters, use the special
241 C<"U0"> prefix. It consumes no arguments but forces the result to be
242 in Unicode characters, instead of bytes.
244 my $chars = pack("U0U*", 0x80, 0xFF);
246 =head2 Handling Unicode
248 Handling Unicode is for the most part transparent: just use the
249 strings as usual. Functions like C<index()>, C<length()>, and
250 C<substr()> will work on the Unicode characters; regular expressions
251 will work on the Unicode characters (see L<perlunicode> and L<perlretut>).
253 Note that Perl does B<not> consider combining character sequences
254 to be characters, such for example
256 use charnames ':full';
257 print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n";
259 will print 2, not 1. The only exception is that regular expressions
260 have C<\X> for matching a combining character sequence.
262 When life is not quite so transparent is working with legacy
263 encodings, and I/O, and certain special cases.
265 =head2 Legacy Encodings
267 When you combine legacy data and Unicode the legacy data needs
268 to be upgraded to Unicode. Normally ISO 8859-1 (or EBCDIC, if
269 applicable) is assumed. You can override this assumption by
270 using the C<encoding> pragma, for example
272 use encoding 'latin2'; # ISO 8859-2
274 in which case literals (string or regular expression) and chr/ord
275 in your whole script are assumed to produce Unicode characters from
276 ISO 8859-2 code points. Note that the matching for the encoding
277 names is forgiving: instead of C<latin2> you could have said
278 C<Latin 2>, or C<iso8859-2>, and so forth. With just
282 the environment variable C<PERL_ENCODING> will be consulted,
283 but if that doesn't exist, the encoding pragma fails.
285 The C<Encode> module knows about many encodings and it has interfaces
286 for doing conversions between those encodings:
288 use Encode 'from_to';
289 from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8
293 Normally, writing out Unicode data
295 print FH $some_string_with_unicode, "\n";
297 produces raw bytes that Perl happens to use to internally encode the
298 Unicode string (which depends on the system, as well as what
299 characters happen to be in the string at the time). If any of the
300 characters are at code points 0x100 or above, you will get a warning.
301 To ensure that the output is explicitly rendered in the encoding you
302 desire (and to avoid the warning), open the stream with the desired
303 encoding. Some examples:
305 open FH, ">:utf8", "file";
307 open FH, ">:encoding(ucs2)", "file";
308 open FH, ">:encoding(UTF-8)", "file";
309 open FH, ">:encoding(shift_jis)", "file";
311 and on already open streams use C<binmode()>:
313 binmode(STDOUT, ":utf8");
315 binmode(STDOUT, ":encoding(ucs2)");
316 binmode(STDOUT, ":encoding(UTF-8)");
317 binmode(STDOUT, ":encoding(shift_jis)");
319 The matching of encoding names is loose: case does not matter, and
320 many encodings have several aliases. Note that C<:utf8> discipline
321 must always be specified exactly like that, it is not subject to the
322 loose matching of encoding names.
324 See L<PerlIO> for the C<:utf8> layer;
325 L<PerlIO::encoding> and L<Encode::PerlIO> for the C<:encoding()> layer;
326 L<Encode::Supported> for many encodings supported by the C<Encode> module.
328 Reading in a file that you know happens to be encoded in one of the
329 Unicode encodings does not magically turn the data into Unicode in
330 Perl's eyes. To do that, specify the appropriate discipline when
333 open(my $fh,'<:utf8', 'anything');
334 my $line_of_unicode = <$fh>;
336 open(my $fh,'<:encoding(Big5)', 'anything');
337 my $line_of_unicode = <$fh>;
339 The I/O disciplines can also be specified more flexibly with
340 the C<open> pragma; see L<open>:
342 use open ':utf8'; # input and output default discipline will be UTF-8
344 print X chr(0x100), "\n";
347 printf "%#x\n", ord(<Y>); # this should print 0x100
350 With the C<open> pragma you can use the C<:locale> discipline
352 $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R';
353 # the :locale will probe the locale environment variables like LC_ALL
354 use open OUT => ':locale'; # russki parusski
356 print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1
359 printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1
362 or you can also use the C<':encoding(...)'> discipline
364 open(my $epic,'<:encoding(iso-8859-7)','iliad.greek');
365 my $line_of_unicode = <$epic>;
367 These methods install a transparent filter on the I/O stream that
368 converts data from the specified encoding when it is read in from the
369 stream. The result is always Unicode.
371 The L<open> pragma affects all the C<open()> calls after the pragma by
372 setting default disciplines. If you want to affect only certain
373 streams, use explicit disciplines directly in the C<open()> call.
375 You can switch encodings on an already opened stream by using
376 C<binmode()>; see L<perlfunc/binmode>.
378 The C<:locale> does not currently (as of Perl 5.8.0) work with
379 C<open()> and C<binmode()>, only with the C<open> pragma. The
380 C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>,
381 C<binmode()>, and the C<open> pragma.
383 Similarly, you may use these I/O disciplines on output streams to
384 automatically convert Unicode to the specified encoding when it is
385 written to the stream. For example, the following snippet copies the
386 contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to
387 the file "text.utf8", encoded as UTF-8:
389 open(my $nihongo, '<:encoding(iso2022-jp)', 'text.jis');
390 open(my $unicode, '>:utf8', 'text.utf8');
391 while (<$nihongo>) { print $unicode }
393 The naming of encodings, both by the C<open()> and by the C<open>
394 pragma, is similarly understanding as with the C<encoding> pragma:
395 C<koi8-r> and C<KOI8R> will both be understood.
397 Common encodings recognized by ISO, MIME, IANA, and various other
398 standardisation organisations are recognised; for a more detailed
401 C<read()> reads characters and returns the number of characters.
402 C<seek()> and C<tell()> operate on byte counts, as do C<sysread()>
405 Notice that because of the default behaviour of not doing any
406 conversion upon input if there is no default discipline,
407 it is easy to mistakenly write code that keeps on expanding a file
408 by repeatedly encoding:
412 local $/; ## read in the whole file of 8-bit characters
415 open F, ">:utf8", "file";
416 print F $t; ## convert to UTF-8 on output
419 If you run this code twice, the contents of the F<file> will be twice
420 UTF-8 encoded. A C<use open ':utf8'> would have avoided the bug, or
421 explicitly opening also the F<file> for input as UTF-8.
423 B<NOTE>: the C<:utf8> and C<:encoding> features work only if your
424 Perl has been built with the new "perlio" feature. Almost all
425 Perl 5.8 platforms do use "perlio", though: you can see whether
426 yours is by running "perl -V" and looking for C<useperlio=define>.
428 =head2 Displaying Unicode As Text
430 Sometimes you might want to display Perl scalars containing Unicode as
431 simple ASCII (or EBCDIC) text. The following subroutine converts
432 its argument so that Unicode characters with code points greater than
433 255 are displayed as "\x{...}", control characters (like "\n") are
434 displayed as "\x..", and the rest of the characters as themselves:
438 map { $_ > 255 ? # if wide character...
439 sprintf("\\x{%04X}", $_) : # \x{...}
440 chr($_) =~ /[[:cntrl:]]/ ? # else if control character ...
441 sprintf("\\x%02X", $_) : # \x..
442 chr($_) # else as themselves
443 } unpack("U*", $_[0])); # unpack Unicode characters
448 nice_string("foo\x{100}bar\n")
460 Bit Complement Operator ~ And vec()
462 The bit complement operator C<~> may produce surprising results if used on
463 strings containing characters with ordinal values above 255. In such a
464 case, the results are consistent with the internal encoding of the
465 characters, but not with much else. So don't do that. Similarly for vec():
466 you will be operating on the internally encoded bit patterns of the Unicode
467 characters, not on the code point values, which is very probably not what
472 Peeking At Perl's Internal Encoding
474 Normal users of Perl should never care how Perl encodes any particular
475 Unicode string (because the normal ways to get at the contents of a
476 string with Unicode -- via input and output -- should always be via
477 explicitly-defined I/O disciplines). But if you must, there are two
478 ways of looking behind the scenes.
480 One way of peeking inside the internal encoding of Unicode characters
481 is to use C<unpack("C*", ...> to get the bytes, or C<unpack("H*", ...)>
482 to display the bytes:
484 # this prints c4 80 for the UTF-8 bytes 0xc4 0x80
485 print join(" ", unpack("H*", pack("U", 0x100))), "\n";
487 Yet another way would be to use the Devel::Peek module:
489 perl -MDevel::Peek -e 'Dump(chr(0x100))'
491 That shows the UTF8 flag in FLAGS and both the UTF-8 bytes
492 and Unicode characters in PV. See also later in this document
493 the discussion about the C<is_utf8> function of the C<Encode> module.
497 =head2 Advanced Topics
505 The question of string equivalence turns somewhat complicated
506 in Unicode: what do you mean by equal?
508 (Is C<LATIN CAPITAL LETTER A WITH ACUTE> equal to
509 C<LATIN CAPITAL LETTER A>?)
511 The short answer is that by default Perl compares equivalence (C<eq>,
512 C<ne>) based only on code points of the characters. In the above
513 case, the answer is no (because 0x00C1 != 0x0041). But sometimes any
514 CAPITAL LETTER As being considered equal, or even any As of any case,
517 The long answer is that you need to consider character normalization
518 and casing issues: see L<Unicode::Normalize>, and Unicode Technical
519 Reports #15 and #21, I<Unicode Normalization Forms> and I<Case
520 Mappings>, http://www.unicode.org/unicode/reports/tr15/
521 http://www.unicode.org/unicode/reports/tr21/
523 As of Perl 5.8.0, regular expression case-ignoring matching
524 implements only 1:1 semantics: one character matches one character.
525 In I<Case Mappings> both 1:N and N:1 matches are defined.
531 People like to see their strings nicely sorted, or as Unicode
532 parlance goes, collated. But again, what do you mean by collate?
534 (Does C<LATIN CAPITAL LETTER A WITH ACUTE> come before or after
535 C<LATIN CAPITAL LETTER A WITH GRAVE>?)
537 The short answer is that by default, Perl compares strings (C<lt>,
538 C<le>, C<cmp>, C<ge>, C<gt>) based only on the code points of the
539 characters. In the above case, the answer is "after", since 0x00C1 > 0x00C0.
541 The long answer is that "it depends", and a good answer cannot be
542 given without knowing (at the very least) the language context.
543 See L<Unicode::Collate>, and I<Unicode Collation Algorithm>
544 http://www.unicode.org/unicode/reports/tr10/
554 Character Ranges and Classes
556 Character ranges in regular expression character classes (C</[a-z]/>)
557 and in the C<tr///> (also known as C<y///>) operator are not magically
558 Unicode-aware. What this means that C<[A-Za-z]> will not magically start
559 to mean "all alphabetic letters" (not that it does mean that even for
560 8-bit characters, you should be using C</[[:alpha:]]/> for that).
562 For specifying things like that in regular expressions, you can use
563 the various Unicode properties, C<\pL> or perhaps C<\p{Alphabetic}>,
564 in this particular case. You can use Unicode code points as the end
565 points of character ranges, but that means that particular code point
566 range, nothing more. For further information (there are dozens
567 of Unicode character classes), see L<perlunicode>.
571 String-To-Number Conversions
573 Unicode does define several other decimal (and numeric) characters
574 than just the familiar 0 to 9, such as the Arabic and Indic digits.
575 Perl does not support string-to-number conversion for digits other
576 than ASCII 0 to 9 (and ASCII a to f for hexadecimal).
580 =head2 Questions With Answers
586 Will My Old Scripts Break?
588 Very probably not. Unless you are generating Unicode characters
589 somehow, any old behaviour should be preserved. About the only
590 behaviour that has changed and which could start generating Unicode
591 is the old behaviour of C<chr()> where supplying an argument more
592 than 255 produced a character modulo 255 (for example, C<chr(300)>
593 was equal to C<chr(45)>).
597 How Do I Make My Scripts Work With Unicode?
599 Very little work should be needed since nothing changes until you
600 somehow generate Unicode data. The greatest trick will be getting
601 input as Unicode, and for that see the earlier I/O discussion.
605 How Do I Know Whether My String Is In Unicode?
607 You shouldn't care. No, you really shouldn't. If you have
608 to care (beyond the cases described above), it means that we
609 didn't get the transparency of Unicode quite right.
613 use Encode 'is_utf8';
614 print is_utf8($string) ? 1 : 0, "\n";
616 But note that this doesn't mean that any of the characters in the
617 string are necessary UTF-8 encoded, or that any of the characters have
618 code points greater than 0xFF (255) or even 0x80 (128), or that the
619 string has any characters at all. All the C<is_utf8()> does is to
620 return the value of the internal "utf8ness" flag attached to the
621 $string. If the flag is off, the bytes in the scalar are interpreted
622 as a single byte encoding. If the flag is on, the bytes in the scalar
623 are interpreted as the (multibyte, variable-length) UTF-8 encoded code
624 points of the characters. Bytes added to an UTF-8 encoded string are
625 automatically upgraded to UTF-8. If mixed non-UTF8 and UTF-8 scalars
626 are merged (doublequoted interpolation, explicit concatenation, and
627 printf/sprintf parameter substitution), the result will be UTF-8 encoded
628 as if copies of the byte strings were upgraded to UTF-8: for example,
634 the output string will be UTF-8-encoded "ab\x80c\x{100}\n", but note
635 that C<$a> will stay single byte encoded.
637 Sometimes you might really need to know the byte length of a string
638 instead of the character length. For that use either the
639 C<Encode::encode_utf8()> function or the C<bytes> pragma and its only
640 defined function C<length()>:
642 my $unicode = chr(0x100);
643 print length($unicode), "\n"; # will print 1
645 print length(Encode::encode_utf8($unicode)), "\n"; # will print 2
647 print length($unicode), "\n"; # will also print 2 (the 0xC4 0x80 of the UTF-8)
651 How Do I Detect Data That's Not Valid In a Particular Encoding?
653 Use the C<Encode> package to try converting it.
656 use Encode 'encode_utf8';
657 if (encode_utf8($string_of_bytes_that_I_think_is_utf8)) {
663 For UTF-8 only, you can use:
666 @chars = unpack("U0U*", $string_of_bytes_that_I_think_is_utf8);
668 If invalid, a C<Malformed UTF-8 character (byte 0x##) in
669 unpack> is produced. The "U0" means "expect strictly UTF-8
670 encoded Unicode". Without that the C<unpack("U*", ...)>
671 would accept also data like C<chr(0xFF>), similarly to the
672 C<pack> as we saw earlier.
676 How Do I Convert Binary Data Into a Particular Encoding, Or Vice Versa?
678 This probably isn't as useful as you might think.
679 Normally, you shouldn't need to.
681 In one sense, what you are asking doesn't make much sense: Encodings
682 are for characters, and binary data is not "characters", so converting
683 "data" into some encoding isn't meaningful unless you know in what
684 character set and encoding the binary data is in, in which case it's
685 not binary data, now is it?
687 If you have a raw sequence of bytes that you know should be interpreted via
688 a particular encoding, you can use C<Encode>:
690 use Encode 'from_to';
691 from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8
693 The call to from_to() changes the bytes in $data, but nothing material
694 about the nature of the string has changed as far as Perl is concerned.
695 Both before and after the call, the string $data contains just a bunch of
696 8-bit bytes. As far as Perl is concerned, the encoding of the string (as
697 Perl sees it) remains as "system-native 8-bit bytes".
699 You might relate this to a fictional 'Translate' module:
703 Translate::from_to($phrase, 'english', 'deutsch');
704 ## phrase now contains "Ja"
706 The contents of the string changes, but not the nature of the string.
707 Perl doesn't know any more after the call than before that the contents
708 of the string indicates the affirmative.
710 Back to converting data, if you have (or want) data in your system's
711 native 8-bit encoding (e.g. Latin-1, EBCDIC, etc.), you can use
712 pack/unpack to convert to/from Unicode.
714 $native_string = pack("C*", unpack("U*", $Unicode_string));
715 $Unicode_string = pack("U*", unpack("C*", $native_string));
717 If you have a sequence of bytes you B<know> is valid UTF-8,
718 but Perl doesn't know it yet, you can make Perl a believer, too:
720 use Encode 'decode_utf8';
721 $Unicode = decode_utf8($bytes);
723 You can convert well-formed UTF-8 to a sequence of bytes, but if
724 you just want to convert random binary data into UTF-8, you can't.
725 Any random collection of bytes isn't well-formed UTF-8. You can
726 use C<unpack("C*", $string)> for the former, and you can create
727 well-formed Unicode data by C<pack("U*", 0xff, ...)>.
731 How Do I Display Unicode? How Do I Input Unicode?
733 See http://www.alanwood.net/unicode/ and
734 http://www.cl.cam.ac.uk/~mgk25/unicode.html
738 How Does Unicode Work With Traditional Locales?
740 In Perl, not very well. Avoid using locales through the C<locale>
741 pragma. Use only one or the other.
745 =head2 Hexadecimal Notation
747 The Unicode standard prefers using hexadecimal notation because that
748 shows better the division of Unicode into blocks of 256 characters.
749 Hexadecimal is also simply shorter than decimal. You can use decimal
750 notation, too, but learning to use hexadecimal just makes life easier
751 with the Unicode standard. The "U+HHHH" notation uses hexadecimal,
754 The C<0x> prefix means a hexadecimal number, the digits are 0-9 I<and>
755 a-f (or A-F, case doesn't matter). Each hexadecimal digit represents
756 four bits, or half a byte. C<print 0x..., "\n"> will show a
757 hexadecimal number in decimal, and C<printf "%x\n", $decimal> will
758 show a decimal number in hexadecimal. If you have just the
759 "hexdigits" of a hexadecimal number, you can use the C<hex()> function.
761 print 0x0009, "\n"; # 9
762 print 0x000a, "\n"; # 10
763 print 0x000f, "\n"; # 15
764 print 0x0010, "\n"; # 16
765 print 0x0011, "\n"; # 17
766 print 0x0100, "\n"; # 256
768 print 0x0041, "\n"; # 65
770 printf "%x\n", 65; # 41
771 printf "%#x\n", 65; # 0x41
773 print hex("41"), "\n"; # 65
775 =head2 Further Resources
783 http://www.unicode.org/
789 http://www.unicode.org/unicode/faq/
795 http://www.unicode.org/glossary/
799 Unicode Useful Resources
801 http://www.unicode.org/unicode/onlinedat/resources.html
805 Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications
807 http://www.alanwood.net/unicode/
811 UTF-8 and Unicode FAQ for Unix/Linux
813 http://www.cl.cam.ac.uk/~mgk25/unicode.html
817 Legacy Character Sets
819 http://www.czyborra.com/
820 http://www.eki.ee/letter/
824 The Unicode support files live within the Perl installation in the
827 $Config{installprivlib}/unicore
829 in Perl 5.8.0 or newer, and
831 $Config{installprivlib}/unicode
833 in the Perl 5.6 series. (The renaming to F<lib/unicore> was done to
834 avoid naming conflicts with lib/Unicode in case-insensitive filesystems.)
835 The main Unicode data file is F<UnicodeData.txt> (or F<Unicode.301> in
836 Perl 5.6.1.) You can find the C<$Config{installprivlib}> by
838 perl "-V:installprivlib"
840 You can explore various information from the Unicode data files using
841 the C<Unicode::UCD> module.
845 =head1 UNICODE IN OLDER PERLS
847 If you cannot upgrade your Perl to 5.8.0 or later, you can still
848 do some Unicode processing by using the modules C<Unicode::String>,
849 C<Unicode::Map8>, and C<Unicode::Map>, available from CPAN.
850 If you have the GNU recode installed, you can also use the
851 Perl frontend C<Convert::Recode> for character conversions.
853 The following are fast conversions from ISO 8859-1 (Latin-1) bytes
854 to UTF-8 bytes, the code works even with older Perl 5 versions.
856 # ISO 8859-1 to UTF-8
857 s/([\x80-\xFF])/chr(0xC0|ord($1)>>6).chr(0x80|ord($1)&0x3F)/eg;
859 # UTF-8 to ISO 8859-1
860 s/([\xC2\xC3])([\x80-\xBF])/chr(ord($1)<<6&0xC0|ord($2)&0x3F)/eg;
864 L<perlunicode>, L<Encode>, L<encoding>, L<open>, L<utf8>, L<bytes>,
865 L<perlretut>, L<Unicode::Collate>, L<Unicode::Normalize>, L<Unicode::UCD>
867 =head1 ACKNOWLEDGEMENTS
869 Thanks to the kind readers of the perl5-porters@perl.org,
870 perl-unicode@perl.org, linux-utf8@nl.linux.org, and unicore@unicode.org
871 mailing lists for their valuable feedback.
873 =head1 AUTHOR, COPYRIGHT, AND LICENSE
875 Copyright 2001-2002 Jarkko Hietaniemi <jhi@iki.fi>
877 This document may be distributed under the same terms as Perl itself.