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 which plans to codify 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 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, especially not to the C language C<char>.
25 Unicode is language-neutral and display-neutral: it does not encode the
26 language of the text and it does not 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 unique numbers for the characters, in this
32 case 0x0041 and 0x03B1, respectively. These unique numbers are called
35 The Unicode standard prefers using hexadecimal notation for the code
36 points. If numbers like "C<0x0041" are 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 to give 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 base character and modifiers is called a I<combining character
54 Whether to call these combining character sequences "characters"
55 depends on your point of view. If you are a programmer, you probably
56 would tend towards seeing each element in the sequences as one unit,
57 or "character". The whole sequence could be seen as one "character",
58 however, from the user's point of view, since that's probably what it
59 looks like in the context of the user's language.
61 With this "whole sequence" view of characters, the total number of
62 characters is open-ended. But in the programmer's "one unit is one
63 character" point of view, the concept of "characters" is more
64 deterministic. In this document, we take that second point of view: one
65 "character" is one Unicode code point, be it a base character or a
68 For some combinations, there are I<precomposed> characters.
69 C<LATIN CAPITAL LETTER A WITH ACUTE>, for example, is defined as
70 a single code point. These precomposed characters are, however,
71 only available for some combinations, and are mainly
72 meant to support round-trip conversions between Unicode and legacy
73 standards (like the ISO 8859). In the general case, the composing
74 method is more extensible. To support conversion between
75 different compositions of the characters, various I<normalization
76 forms> to standardize representations are also defined.
78 Because of backward compatibility with legacy encodings, the "a unique
79 number for every character" idea breaks down a bit: instead, there is
80 "at least one number for every character". The same character could
81 be represented differently in several legacy encodings. The
82 converse is also not true: some code points do not have an assigned
83 character. Firstly, there are unallocated code points within
84 otherwise used blocks. Secondly, there are special Unicode control
85 characters that do not represent true characters.
87 A common myth about Unicode is that it would be "16-bit", that is,
88 Unicode is only represented as C<0x10000> (or 65536) characters from
89 C<0x0000> to C<0xFFFF>. B<This is untrue.> Since Unicode 2.0, Unicode
90 has been defined all the way up to 21 bits (C<0x10FFFF>), and since
91 Unicode 3.1, characters have been defined beyond C<0xFFFF>. The first
92 C<0x10000> characters are called the I<Plane 0>, or the I<Basic
93 Multilingual Plane> (BMP). With Unicode 3.1, 17 planes in all are
94 defined--but nowhere near full of defined characters, yet.
96 Another myth is that the 256-character blocks have something to do
97 with languages--that each languages is specified inside a block.
98 B<This is also untrue.> The division into blocks exists, but it is
99 almost completely accidental--an artifact of how the characters have
100 been historically allocated. Instead, there is a concept called
101 I<scripts>, which is more useful: there is C<Latin> script,
102 C<Greek> script, and so on. Scripts usually span varied parts of
103 several blocks. For further information see L<Unicode::UCD>.
105 The Unicode code points are just abstract numbers. To input and
106 output these abstract numbers, the numbers must be I<encoded> somehow.
107 Unicode defines several I<character encoding forms>, of which I<UTF-8>
108 is perhaps the most popular. UTF-8 is a variable length encoding that
109 encodes Unicode characters as 1 to 6 bytes (only 4 with the currently
110 defined characters). Other encodings include UTF-16 and UTF-32 and their
111 big- and little-endian variants (UTF-8 is byte-order independent).
112 The ISO/IEC 10646 defines the UCS-2 and UCS-4 encoding forms.
114 For more information about encodings--for instance, to learn what
115 I<surrogates> and I<byte order marks> (BOMs) are--see L<perlunicode>.
117 =head2 Perl's Unicode Support
119 Starting from Perl 5.6.0, Perl has had the capacity to handle Unicode
120 natively. Perl 5.8.0, however, is the first recommended release for
121 serious Unicode work. The maintenance release 5.6.1 fixed many of the
122 problems of the initial Unicode implementation, but for example
123 regular expressions did not really work with Unicode.
125 B<Starting from Perl 5.8.0, the use of C<use utf8> is no longer
126 necessary.> In earlier releases the C<utf8> pragma was used to declare
127 that operations in the current block or file would be Unicode-aware.
128 This model was found to be wrong, or at least clumsy: the "Unicodeness"
129 is now carried with the data instead of being attached to the
130 operations. Only one case remains where an explicit C<use utf8> is
131 needed: if your Perl script itself is encoded in UTF-8, you can use
132 UTF-8 in your identifier names, and in string and regular expression
133 literals, by saying C<use utf8>. This is not the default because
134 scripts with legacy 8-bit data in them would break.
136 =head2 Perl's Unicode Model
138 Perl supports both pre-5.6 strings of eight-bit native bytes, and
139 strings of Unicode characters. The principle is that Perl tries to
140 keep its data as eight-bit bytes for as long as possible, but as soon
141 as Unicodeness cannot be avoided, the data is transparently upgraded
144 Internally, Perl currently uses either whatever the native eight-bit
145 character set of the platform (for example Latin-1) is, defaulting to
146 UTF-8, to encode Unicode strings. Specifically, if all code points in
147 the string are C<0xFF> or less, Perl uses the native eight-bit
148 character set. Otherwise, it uses UTF-8.
150 A user of Perl does not normally need to know nor care how Perl
151 happens to encode its internal strings, but it becomes relevant when
152 outputting Unicode strings to a stream without a discipline--one with
153 the "default" encoding. In such a case, the raw bytes used internally
154 (the native character set or UTF-8, as appropriate for each string)
155 will be used, and a "Wide character" warning will be issued if those
156 strings contain a character beyond 0x00FF.
160 perl -e 'print "\x{DF}\n", "\x{0100}\x{DF}\n"'
162 produces a fairly useless mixture of native bytes and UTF-8, as well
165 To output UTF-8 always, use the "C<:utf8>" output discipline. Prepending
167 binmode(STDOUT, ":utf8");
169 to this sample program ensures that the output is completely UTF-8,
170 and helpfully removes the program's warning.
172 If your locale environment variables (C<LANGUAGE>, C<LC_ALL>,
173 C<LC_CTYPE>, C<LANG>) contain the strings 'UTF-8' or 'UTF8',
174 regardless of case, then the default encoding of your STDIN, STDOUT,
175 and STDERR and of B<any subsequent file open>, is UTF-8. Note that
176 this means that Perl expects other software to work, too: if STDIN
177 coming in from another command is not UTF-8, Perl will complain about
180 =head2 Unicode and EBCDIC
182 Perl 5.8.0 also supports Unicode on EBCDIC platforms. There,
183 Unicode support is somewhat more complex to implement since
184 additional conversions are needed at every step. Some problems
185 remain, see L<perlebcdic> for details.
187 In any case, the Unicode support on EBCDIC platforms is better than
188 in the 5.6 series, which didn't work much at all for EBCDIC platform.
189 On EBCDIC platforms, the internal Unicode encoding form is UTF-EBCDIC
190 instead of UTF-8. The difference is that as UTF-8 is "ASCII-safe" in
191 that ASCII characters encode to UTF-8 as-is, while UTF-EBCDIC is
194 =head2 Creating Unicode
196 To create Unicode characters in literals for code points above C<0xFF>,
197 use the C<\x{...}> notation in double-quoted strings:
199 my $smiley = "\x{263a}";
201 Similarly, it can be used in regular expression literals
203 $smiley =~ /\x{263a}/;
205 At run-time you can use C<chr()>:
207 my $hebrew_alef = chr(0x05d0);
209 See L</"Further Resources"> for how to find all these numeric codes.
211 Naturally, C<ord()> will do the reverse: it turns a character into
214 Note that C<\x..> (no C<{}> and only two hexadecimal digits),
215 C<\x{...}>, and C<chr(...)> for arguments less than C<0x100> (decimal
216 256) generate an eight-bit character for backward compatibility with
217 older Perls. For arguments of C<0x100> or more, Unicode characters are
218 always produced. If you want to force the production of Unicode
219 characters regardless of the numeric value, use C<pack("U", ...)>
220 instead of C<\x..>, C<\x{...}>, or C<chr()>.
222 You can also use the C<charnames> pragma to invoke characters
223 by name in double-quoted strings:
225 use charnames ':full';
226 my $arabic_alef = "\N{ARABIC LETTER ALEF}";
228 And, as mentioned above, you can also C<pack()> numbers into Unicode
231 my $georgian_an = pack("U", 0x10a0);
233 Note that both C<\x{...}> and C<\N{...}> are compile-time string
234 constants: you cannot use variables in them. if you want similar
235 run-time functionality, use C<chr()> and C<charnames::vianame()>.
237 Also note that if all the code points for pack "U" are below 0x100,
238 bytes will be generated, just like if you were using C<chr()>.
240 my $bytes = pack("U*", 0x80, 0xFF);
242 If you want to force the result to Unicode characters, use the special
243 C<"U0"> prefix. It consumes no arguments but forces the result to be
244 in Unicode characters, instead of bytes.
246 my $chars = pack("U0U*", 0x80, 0xFF);
248 =head2 Handling Unicode
250 Handling Unicode is for the most part transparent: just use the
251 strings as usual. Functions like C<index()>, C<length()>, and
252 C<substr()> will work on the Unicode characters; regular expressions
253 will work on the Unicode characters (see L<perlunicode> and L<perlretut>).
255 Note that Perl considers combining character sequences
256 to be characters, so for example
258 use charnames ':full';
259 print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n";
261 will print 2, not 1. The only exception is that regular expressions
262 have C<\X> for matching a combining character sequence.
264 Life is not quite so transparent, however, when working with legacy
265 encodings, I/O, and certain special cases:
267 =head2 Legacy Encodings
269 When you combine legacy data and Unicode the legacy data needs
270 to be upgraded to Unicode. Normally ISO 8859-1 (or EBCDIC, if
271 applicable) is assumed. You can override this assumption by
272 using the C<encoding> pragma, for example
274 use encoding 'latin2'; # ISO 8859-2
276 in which case literals (string or regular expressions), C<chr()>, and
277 C<ord()> in your whole script are assumed to produce Unicode
278 characters from ISO 8859-2 code points. Note that the matching for
279 encoding names is forgiving: instead of C<latin2> you could have
280 said C<Latin 2>, or C<iso8859-2>, or other variations. With just
284 the environment variable C<PERL_ENCODING> will be consulted.
285 If that variable isn't set, the encoding pragma will fail.
287 The C<Encode> module knows about many encodings and has interfaces
288 for doing conversions between those encodings:
290 use Encode 'from_to';
291 from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8
295 Normally, writing out Unicode data
297 print FH $some_string_with_unicode, "\n";
299 produces raw bytes that Perl happens to use to internally encode the
300 Unicode string. Perl's internal encoding depends on the system as
301 well as what characters happen to be in the string at the time. If
302 any of the characters are at code points C<0x100> or above, you will get
303 a warning. To ensure that the output is explicitly rendered in the
304 encoding you desire--and to avoid the warning--open the stream with
305 the desired encoding. Some examples:
307 open FH, ">:utf8", "file";
309 open FH, ">:encoding(ucs2)", "file";
310 open FH, ">:encoding(UTF-8)", "file";
311 open FH, ">:encoding(shift_jis)", "file";
313 and on already open streams, use C<binmode()>:
315 binmode(STDOUT, ":utf8");
317 binmode(STDOUT, ":encoding(ucs2)");
318 binmode(STDOUT, ":encoding(UTF-8)");
319 binmode(STDOUT, ":encoding(shift_jis)");
321 The matching of encoding names is loose: case does not matter, and
322 many encodings have several aliases. Note that C<:utf8> discipline
323 must always be specified exactly like that; it is I<not> subject to the
324 loose matching of encoding names.
326 See L<PerlIO> for the C<:utf8> layer, L<PerlIO::encoding> and
327 L<Encode::PerlIO> for the C<:encoding()> layer, and
328 L<Encode::Supported> for many encodings supported by the C<Encode>
331 Reading in a file that you know happens to be encoded in one of the
332 Unicode encodings does not magically turn the data into Unicode in
333 Perl's eyes. To do that, specify the appropriate discipline when
336 open(my $fh,'<:utf8', 'anything');
337 my $line_of_unicode = <$fh>;
339 open(my $fh,'<:encoding(Big5)', 'anything');
340 my $line_of_unicode = <$fh>;
342 The I/O disciplines can also be specified more flexibly with
343 the C<open> pragma. See L<open>, or look at the following example.
345 use open ':utf8'; # input and output default discipline will be UTF-8
347 print X chr(0x100), "\n";
350 printf "%#x\n", ord(<Y>); # this should print 0x100
353 With the C<open> pragma you can use the C<:locale> discipline
355 $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R';
356 # the :locale will probe the locale environment variables like LC_ALL
357 use open OUT => ':locale'; # russki parusski
359 print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1
362 printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1
365 or you can also use the C<':encoding(...)'> discipline
367 open(my $epic,'<:encoding(iso-8859-7)','iliad.greek');
368 my $line_of_unicode = <$epic>;
370 These methods install a transparent filter on the I/O stream that
371 converts data from the specified encoding when it is read in from the
372 stream. The result is always Unicode.
374 The L<open> pragma affects all the C<open()> calls after the pragma by
375 setting default disciplines. If you want to affect only certain
376 streams, use explicit disciplines directly in the C<open()> call.
378 You can switch encodings on an already opened stream by using
379 C<binmode()>; see L<perlfunc/binmode>.
381 The C<:locale> does not currently (as of Perl 5.8.0) work with
382 C<open()> and C<binmode()>, only with the C<open> pragma. The
383 C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>,
384 C<binmode()>, and the C<open> pragma.
386 Similarly, you may use these I/O disciplines on output streams to
387 automatically convert Unicode to the specified encoding when it is
388 written to the stream. For example, the following snippet copies the
389 contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to
390 the file "text.utf8", encoded as UTF-8:
392 open(my $nihongo, '<:encoding(iso2022-jp)', 'text.jis');
393 open(my $unicode, '>:utf8', 'text.utf8');
394 while (<$nihongo>) { print $unicode }
396 The naming of encodings, both by the C<open()> and by the C<open>
397 pragma, is similar to the C<encoding> pragma in that it allows for
398 flexible names: C<koi8-r> and C<KOI8R> will both be understood.
400 Common encodings recognized by ISO, MIME, IANA, and various other
401 standardisation organisations are recognised; for a more detailed
404 C<read()> reads characters and returns the number of characters.
405 C<seek()> and C<tell()> operate on byte counts, as do C<sysread()>
408 Notice that because of the default behaviour of not doing any
409 conversion upon input if there is no default discipline,
410 it is easy to mistakenly write code that keeps on expanding a file
411 by repeatedly encoding:
415 local $/; ## read in the whole file of 8-bit characters
418 open F, ">:utf8", "file";
419 print F $t; ## convert to UTF-8 on output
422 If you run this code twice, the contents of the F<file> will be twice
423 UTF-8 encoded. A C<use open ':utf8'> would have avoided the bug, or
424 explicitly opening also the F<file> for input as UTF-8.
426 B<NOTE>: the C<:utf8> and C<:encoding> features work only if your
427 Perl has been built with the new "perlio" feature. Almost all
428 Perl 5.8 platforms do use "perlio", though: you can see whether
429 yours is by running "perl -V" and looking for C<useperlio=define>.
431 =head2 Displaying Unicode As Text
433 Sometimes you might want to display Perl scalars containing Unicode as
434 simple ASCII (or EBCDIC) text. The following subroutine converts
435 its argument so that Unicode characters with code points greater than
436 255 are displayed as "C<\x{...}>", control characters (like "C<\n>") are
437 displayed as "C<\x..>", and the rest of the characters as themselves:
441 map { $_ > 255 ? # if wide character...
442 sprintf("\\x{%04X}", $_) : # \x{...}
443 chr($_) =~ /[[:cntrl:]]/ ? # else if control character ...
444 sprintf("\\x%02X", $_) : # \x..
445 chr($_) # else as themselves
446 } unpack("U*", $_[0])); # unpack Unicode characters
451 nice_string("foo\x{100}bar\n")
463 Bit Complement Operator ~ And vec()
465 The bit complement operator C<~> may produce surprising results if used on
466 strings containing characters with ordinal values above 255. In such a
467 case, the results are consistent with the internal encoding of the
468 characters, but not with much else. So don't do that. Similarly for C<vec()>:
469 you will be operating on the internally-encoded bit patterns of the Unicode
470 characters, not on the code point values, which is very probably not what
475 Peeking At Perl's Internal Encoding
477 Normal users of Perl should never care how Perl encodes any particular
478 Unicode string (because the normal ways to get at the contents of a
479 string with Unicode--via input and output--should always be via
480 explicitly-defined I/O disciplines). But if you must, there are two
481 ways of looking behind the scenes.
483 One way of peeking inside the internal encoding of Unicode characters
484 is to use C<unpack("C*", ...> to get the bytes or C<unpack("H*", ...)>
485 to display the bytes:
487 # this prints c4 80 for the UTF-8 bytes 0xc4 0x80
488 print join(" ", unpack("H*", pack("U", 0x100))), "\n";
490 Yet another way would be to use the Devel::Peek module:
492 perl -MDevel::Peek -e 'Dump(chr(0x100))'
494 That shows the UTF8 flag in FLAGS and both the UTF-8 bytes
495 and Unicode characters in C<PV>. See also later in this document
496 the discussion about the C<is_utf8> function of the C<Encode> module.
500 =head2 Advanced Topics
508 The question of string equivalence turns somewhat complicated
509 in Unicode: what do you mean by "equal"?
511 (Is C<LATIN CAPITAL LETTER A WITH ACUTE> equal to
512 C<LATIN CAPITAL LETTER A>?)
514 The short answer is that by default Perl compares equivalence (C<eq>,
515 C<ne>) based only on code points of the characters. In the above
516 case, the answer is no (because 0x00C1 != 0x0041). But sometimes, any
517 CAPITAL LETTER As should be considered equal, or even As of any case.
519 The long answer is that you need to consider character normalization
520 and casing issues: see L<Unicode::Normalize>, Unicode Technical
521 Reports #15 and #21, I<Unicode Normalization Forms> and I<Case
522 Mappings>, http://www.unicode.org/unicode/reports/tr15/ and
523 http://www.unicode.org/unicode/reports/tr21/
525 As of Perl 5.8.0, regular expression case-ignoring matching
526 implements only 1:1 semantics: one character matches one character.
527 In I<Case Mappings> both 1:N and N:1 matches are defined.
533 People like to see their strings nicely sorted--or as Unicode
534 parlance goes, collated. But again, what do you mean by collate?
536 (Does C<LATIN CAPITAL LETTER A WITH ACUTE> come before or after
537 C<LATIN CAPITAL LETTER A WITH GRAVE>?)
539 The short answer is that by default, Perl compares strings (C<lt>,
540 C<le>, C<cmp>, C<ge>, C<gt>) based only on the code points of the
541 characters. In the above case, the answer is "after", since C<0x00C1>
544 The long answer is that "it depends", and a good answer cannot be
545 given without knowing (at the very least) the language context.
546 See L<Unicode::Collate>, and I<Unicode Collation Algorithm>
547 http://www.unicode.org/unicode/reports/tr10/
557 Character Ranges and Classes
559 Character ranges in regular expression character classes (C</[a-z]/>)
560 and in the C<tr///> (also known as C<y///>) operator are not magically
561 Unicode-aware. What this means that C<[A-Za-z]> will not magically start
562 to mean "all alphabetic letters"; not that it does mean that even for
563 8-bit characters, you should be using C</[[:alpha:]]/> in that case.
565 For specifying character classes like that in regular expressions, you can use
566 the various Unicode properties--C<\pL>, or perhaps C<\p{Alphabetic}>,
567 in this particular case. You can use Unicode code points as the end
568 points of character ranges, but there is no magic associated with
569 specifying a certain range. For further information--there are dozens
570 of Unicode character classes--see L<perlunicode>.
574 String-To-Number Conversions
576 Unicode does define several other decimal--and numeric--characters
577 besides the familiar 0 to 9, such as the Arabic and Indic digits.
578 Perl does not support string-to-number conversion for digits other
579 than ASCII 0 to 9 (and ASCII a to f for hexadecimal).
583 =head2 Questions With Answers
589 Will My Old Scripts Break?
591 Very probably not. Unless you are generating Unicode characters
592 somehow, old behaviour should be preserved. About the only
593 behaviour that has changed and which could start generating Unicode
594 is the old behaviour of C<chr()> where supplying an argument more
595 than 255 produced a character modulo 255. C<chr(300)>, for example,
596 was equal to C<chr(45)>.
600 How Do I Make My Scripts Work With Unicode?
602 Very little work should be needed since nothing changes until you
603 generate Unicode data. The trick is getting input as Unicode; for
604 that, see the earlier I/O discussion.
608 How Do I Know Whether My String Is In Unicode?
610 You shouldn't care. No, you really shouldn't. No, really. If you have
611 to care--beyond the cases described above--it means that we
612 didn't get the transparency of Unicode quite right.
616 use Encode 'is_utf8';
617 print is_utf8($string) ? 1 : 0, "\n";
619 But note that this doesn't mean that any of the characters in the
620 string are necessary UTF-8 encoded, or that any of the characters have
621 code points greater than 0xFF (255) or even 0x80 (128), or that the
622 string has any characters at all. All the C<is_utf8()> does is to
623 return the value of the internal "utf8ness" flag attached to the
624 C<$string>. If the flag is off, the bytes in the scalar are interpreted
625 as a single byte encoding. If the flag is on, the bytes in the scalar
626 are interpreted as the (multi-byte, variable-length) UTF-8 encoded code
627 points of the characters. Bytes added to an UTF-8 encoded string are
628 automatically upgraded to UTF-8. If mixed non-UTF8 and UTF-8 scalars
629 are merged (double-quoted interpolation, explicit concatenation, and
630 printf/sprintf parameter substitution), the result will be UTF-8 encoded
631 as if copies of the byte strings were upgraded to UTF-8: for example,
637 the output string will be UTF-8-encoded "C<ab\x80c\x{100}\n>", but note
638 that C<$a> will stay byte-encoded.
640 Sometimes you might really need to know the byte length of a string
641 instead of the character length. For that use either the
642 C<Encode::encode_utf8()> function or the C<bytes> pragma and its only
643 defined function C<length()>:
645 my $unicode = chr(0x100);
646 print length($unicode), "\n"; # will print 1
648 print length(Encode::encode_utf8($unicode)), "\n"; # will print 2
650 print length($unicode), "\n"; # will also print 2 (the 0xC4 0x80 of the UTF-8)
654 How Do I Detect Data That's Not Valid In a Particular Encoding?
656 Use the C<Encode> package to try converting it.
659 use Encode 'encode_utf8';
660 if (encode_utf8($string_of_bytes_that_I_think_is_utf8)) {
666 For UTF-8 only, you can use:
669 @chars = unpack("U0U*", $string_of_bytes_that_I_think_is_utf8);
671 If invalid, a C<Malformed UTF-8 character (byte 0x##) in
672 unpack> warning is produced. The "U0" means "expect strictly UTF-8
673 encoded Unicode". Without that the C<unpack("U*", ...)>
674 would accept also data like C<chr(0xFF>), similarly to the
675 C<pack> as we saw earlier.
679 How Do I Convert Binary Data Into a Particular Encoding, Or Vice Versa?
681 This probably isn't as useful as you might think.
682 Normally, you shouldn't need to.
684 In one sense, what you are asking doesn't make much sense: Encodings
685 are for characters, and binary data are not "characters", so converting
686 "data" into some encoding isn't meaningful unless you know in what
687 character set and encoding the binary data is in, in which case it's
688 not just binary data, now is it?
690 If you have a raw sequence of bytes that you know should be interpreted via
691 a particular encoding, you can use C<Encode>:
693 use Encode 'from_to';
694 from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8
696 The call to C<from_to()> changes the bytes in C<$data>, but nothing material
697 about the nature of the string has changed as far as Perl is concerned.
698 Both before and after the call, the string C<$data> contains just a bunch of
699 8-bit bytes. As far as Perl is concerned, the encoding of the string
700 remains as "system-native 8-bit bytes".
702 You might relate this to a fictional 'Translate' module:
706 Translate::from_to($phrase, 'english', 'deutsch');
707 ## phrase now contains "Ja"
709 The contents of the string changes, but not the nature of the string.
710 Perl doesn't know any more after the call than before that the contents
711 of the string indicates the affirmative.
713 Back to converting data. If you have (or want) data in your system's
714 native 8-bit encoding (e.g. Latin-1, EBCDIC, etc.), you can use
715 pack/unpack to convert to/from Unicode.
717 $native_string = pack("C*", unpack("U*", $Unicode_string));
718 $Unicode_string = pack("U*", unpack("C*", $native_string));
720 If you have a sequence of bytes you B<know> is valid UTF-8,
721 but Perl doesn't know it yet, you can make Perl a believer, too:
723 use Encode 'decode_utf8';
724 $Unicode = decode_utf8($bytes);
726 You can convert well-formed UTF-8 to a sequence of bytes, but if
727 you just want to convert random binary data into UTF-8, you can't.
728 Any random collection of bytes isn't well-formed UTF-8. You can
729 use C<unpack("C*", $string)> for the former, and you can create
730 well-formed Unicode data by C<pack("U*", 0xff, ...)>.
734 How Do I Display Unicode? How Do I Input Unicode?
736 See http://www.alanwood.net/unicode/ and
737 http://www.cl.cam.ac.uk/~mgk25/unicode.html
741 How Does Unicode Work With Traditional Locales?
743 In Perl, not very well. Avoid using locales through the C<locale>
744 pragma. Use only one or the other.
748 =head2 Hexadecimal Notation
750 The Unicode standard prefers using hexadecimal notation because
751 that more clearly shows the division of Unicode into blocks of 256 characters.
752 Hexadecimal is also simply shorter than decimal. You can use decimal
753 notation, too, but learning to use hexadecimal just makes life easier
754 with the Unicode standard. The "C<U+HHHH>" notation uses hexadecimal,
757 The C<0x> prefix means a hexadecimal number, the digits are 0-9 I<and>
758 a-f (or A-F, case doesn't matter). Each hexadecimal digit represents
759 four bits, or half a byte. C<print 0x..., "\n"> will show a
760 hexadecimal number in decimal, and C<printf "%x\n", $decimal> will
761 show a decimal number in hexadecimal. If you have just the
762 "hex digits" of a hexadecimal number, you can use the C<hex()> function.
764 print 0x0009, "\n"; # 9
765 print 0x000a, "\n"; # 10
766 print 0x000f, "\n"; # 15
767 print 0x0010, "\n"; # 16
768 print 0x0011, "\n"; # 17
769 print 0x0100, "\n"; # 256
771 print 0x0041, "\n"; # 65
773 printf "%x\n", 65; # 41
774 printf "%#x\n", 65; # 0x41
776 print hex("41"), "\n"; # 65
778 =head2 Further Resources
786 http://www.unicode.org/
792 http://www.unicode.org/unicode/faq/
798 http://www.unicode.org/glossary/
802 Unicode Useful Resources
804 http://www.unicode.org/unicode/onlinedat/resources.html
808 Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications
810 http://www.alanwood.net/unicode/
814 UTF-8 and Unicode FAQ for Unix/Linux
816 http://www.cl.cam.ac.uk/~mgk25/unicode.html
820 Legacy Character Sets
822 http://www.czyborra.com/
823 http://www.eki.ee/letter/
827 The Unicode support files live within the Perl installation in the
830 $Config{installprivlib}/unicore
832 in Perl 5.8.0 or newer, and
834 $Config{installprivlib}/unicode
836 in the Perl 5.6 series. (The renaming to F<lib/unicore> was done to
837 avoid naming conflicts with lib/Unicode in case-insensitive filesystems.)
838 The main Unicode data file is F<UnicodeData.txt> (or F<Unicode.301> in
839 Perl 5.6.1.) You can find the C<$Config{installprivlib}> by
841 perl "-V:installprivlib"
843 You can explore various information from the Unicode data files using
844 the C<Unicode::UCD> module.
848 =head1 UNICODE IN OLDER PERLS
850 If you cannot upgrade your Perl to 5.8.0 or later, you can still
851 do some Unicode processing by using the modules C<Unicode::String>,
852 C<Unicode::Map8>, and C<Unicode::Map>, available from CPAN.
853 If you have the GNU recode installed, you can also use the
854 Perl front-end C<Convert::Recode> for character conversions.
856 The following are fast conversions from ISO 8859-1 (Latin-1) bytes
857 to UTF-8 bytes, the code works even with older Perl 5 versions.
859 # ISO 8859-1 to UTF-8
860 s/([\x80-\xFF])/chr(0xC0|ord($1)>>6).chr(0x80|ord($1)&0x3F)/eg;
862 # UTF-8 to ISO 8859-1
863 s/([\xC2\xC3])([\x80-\xBF])/chr(ord($1)<<6&0xC0|ord($2)&0x3F)/eg;
867 L<perlunicode>, L<Encode>, L<encoding>, L<open>, L<utf8>, L<bytes>,
868 L<perlretut>, L<Unicode::Collate>, L<Unicode::Normalize>, L<Unicode::UCD>
870 =head1 ACKNOWLEDGMENTS
872 Thanks to the kind readers of the perl5-porters@perl.org,
873 perl-unicode@perl.org, linux-utf8@nl.linux.org, and unicore@unicode.org
874 mailing lists for their valuable feedback.
876 =head1 AUTHOR, COPYRIGHT, AND LICENSE
878 Copyright 2001-2002 Jarkko Hietaniemi <jhi@iki.fi>
880 This document may be distributed under the same terms as Perl itself.