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1 | =head1 NAME |
2 | ||
07fcf8ff | 3 | perluniintro - Perl Unicode introduction |
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4 | |
5 | =head1 DESCRIPTION | |
6 | ||
7 | This document gives a general idea of Unicode and how to use Unicode | |
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8 | in Perl. See L</Further Resources> for references to more in-depth |
9 | treatments of Unicode. | |
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10 | |
11 | =head2 Unicode | |
12 | ||
376d9008 | 13 | Unicode is a character set standard which plans to codify all of the |
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14 | writing systems of the world, plus many other symbols. |
15 | ||
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16 | Unicode and ISO/IEC 10646 are coordinated standards that unify |
17 | almost all other modern character set standards, | |
18 | covering more than 80 writing systems and hundreds of languages, | |
376d9008 | 19 | including all commercially-important modern languages. All characters |
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20 | in the largest Chinese, Japanese, and Korean dictionaries are also |
21 | encoded. The standards will eventually cover almost all characters in | |
22 | more than 250 writing systems and thousands of languages. | |
c8695642 | 23 | Unicode 1.0 was released in October 1991, and 6.0 in October 2010. |
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24 | |
25 | A Unicode I<character> is an abstract entity. It is not bound to any | |
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26 | particular integer width, especially not to the C language C<char>. |
27 | Unicode is language-neutral and display-neutral: it does not encode the | |
e1b711da | 28 | language of the text, and it does not generally define fonts or other graphical |
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29 | layout details. Unicode operates on characters and on text built from |
30 | those characters. | |
31 | ||
32 | Unicode defines characters like C<LATIN CAPITAL LETTER A> or C<GREEK | |
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33 | SMALL LETTER ALPHA> and unique numbers for the characters, in this |
34 | case 0x0041 and 0x03B1, respectively. These unique numbers are called | |
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35 | I<code points>. A code point is essentially the position of the |
36 | character within the set of all possible Unicode characters, and thus in | |
37 | Perl, the term I<ordinal> is often used interchangeably with it. | |
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38 | |
39 | The Unicode standard prefers using hexadecimal notation for the code | |
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40 | points. If numbers like C<0x0041> are unfamiliar to you, take a peek |
41 | at a later section, L</"Hexadecimal Notation">. The Unicode standard | |
42 | uses the notation C<U+0041 LATIN CAPITAL LETTER A>, to give the | |
43 | hexadecimal code point and the normative name of the character. | |
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44 | |
45 | Unicode also defines various I<properties> for the characters, like | |
376d9008 | 46 | "uppercase" or "lowercase", "decimal digit", or "punctuation"; |
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47 | these properties are independent of the names of the characters. |
48 | Furthermore, various operations on the characters like uppercasing, | |
376d9008 | 49 | lowercasing, and collating (sorting) are defined. |
ba62762e | 50 | |
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51 | A Unicode I<logical> "character" can actually consist of more than one internal |
52 | I<actual> "character" or code point. For Western languages, this is adequately | |
c670e63a | 53 | modelled by a I<base character> (like C<LATIN CAPITAL LETTER A>) followed |
0111a78f | 54 | by one or more I<modifiers> (like C<COMBINING ACUTE ACCENT>). This sequence of |
376d9008 | 55 | base character and modifiers is called a I<combining character |
0111a78f | 56 | sequence>. Some non-western languages require more complicated |
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57 | models, so Unicode created the I<grapheme cluster> concept, which was |
58 | later further refined into the I<extended grapheme cluster>. For | |
59 | example, a Korean Hangul syllable is considered a single logical | |
60 | character, but most often consists of three actual | |
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61 | Unicode characters: a leading consonant followed by an interior vowel followed |
62 | by a trailing consonant. | |
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63 | |
64 | Whether to call these extended grapheme clusters "characters" depends on your | |
65 | point of view. If you are a programmer, you probably would tend towards seeing | |
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66 | each element in the sequences as one unit, or "character". However from |
67 | the user's point of view, the whole sequence could be seen as one | |
68 | "character" since that's probably what it looks like in the context of the | |
69 | user's language. In this document, we take the programmer's point of | |
70 | view: one "character" is one Unicode code point. | |
71 | ||
72 | For some combinations of base character and modifiers, there are | |
73 | I<precomposed> characters. There is a single character equivalent, for | |
4d2d7a4c | 74 | example, for the sequence C<LATIN CAPITAL LETTER A> followed by |
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75 | C<COMBINING ACUTE ACCENT>. It is called C<LATIN CAPITAL LETTER A WITH |
76 | ACUTE>. These precomposed characters are, however, only available for | |
77 | some combinations, and are mainly meant to support round-trip | |
78 | conversions between Unicode and legacy standards (like ISO 8859). Using | |
79 | sequences, as Unicode does, allows for needing fewer basic building blocks | |
80 | (code points) to express many more potential grapheme clusters. To | |
81 | support conversion between equivalent forms, various I<normalization | |
82 | forms> are also defined. Thus, C<LATIN CAPITAL LETTER A WITH ACUTE> is | |
83 | in I<Normalization Form Composed>, (abbreviated NFC), and the sequence | |
84 | C<LATIN CAPITAL LETTER A> followed by C<COMBINING ACUTE ACCENT> | |
85 | represents the same character in I<Normalization Form Decomposed> (NFD). | |
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86 | |
87 | Because of backward compatibility with legacy encodings, the "a unique | |
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88 | number for every character" idea breaks down a bit: instead, there is |
89 | "at least one number for every character". The same character could | |
90 | be represented differently in several legacy encodings. The | |
91a927c1 | 91 | converse is not true: some code points do not have an assigned |
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92 | character. Firstly, there are unallocated code points within |
93 | otherwise used blocks. Secondly, there are special Unicode control | |
94 | characters that do not represent true characters. | |
ba62762e | 95 | |
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96 | When Unicode was first conceived, it was thought that all the world's |
97 | characters could be represented using a 16-bit word; that is a maximum of | |
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98 | C<0x10000> (or 65,536) characters would be needed, from C<0x0000> to |
99 | C<0xFFFF>. This soon proved to be wrong, and since Unicode 2.0 (July | |
4c496f0c | 100 | 1996), Unicode has been defined all the way up to 21 bits (C<0x10FFFF>), |
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101 | and Unicode 3.1 (March 2001) defined the first characters above C<0xFFFF>. |
102 | The first C<0x10000> characters are called the I<Plane 0>, or the | |
103 | I<Basic Multilingual Plane> (BMP). With Unicode 3.1, 17 (yes, | |
104 | seventeen) planes in all were defined--but they are nowhere near full of | |
105 | defined characters, yet. | |
106 | ||
107 | When a new language is being encoded, Unicode generally will choose a | |
108 | C<block> of consecutive unallocated code points for its characters. So | |
109 | far, the number of code points in these blocks has always been evenly | |
110 | divisible by 16. Extras in a block, not currently needed, are left | |
111 | unallocated, for future growth. But there have been occasions when | |
30189633 | 112 | a later release needed more code points than the available extras, and a |
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113 | new block had to allocated somewhere else, not contiguous to the initial |
114 | one, to handle the overflow. Thus, it became apparent early on that | |
fc273927 | 115 | "block" wasn't an adequate organizing principle, and so the C<Script> |
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116 | property was created. (Later an improved script property was added as |
117 | well, the C<Script_Extensions> property.) Those code points that are in | |
118 | overflow blocks can still | |
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119 | have the same script as the original ones. The script concept fits more |
120 | closely with natural language: there is C<Latin> script, C<Greek> | |
121 | script, and so on; and there are several artificial scripts, like | |
122 | C<Common> for characters that are used in multiple scripts, such as | |
123 | mathematical symbols. Scripts usually span varied parts of several | |
124 | blocks. For more information about scripts, see L<perlunicode/Scripts>. | |
1bfb14c4 | 125 | The division into blocks exists, but it is almost completely |
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126 | accidental--an artifact of how the characters have been and still are |
127 | allocated. (Note that this paragraph has oversimplified things for the | |
128 | sake of this being an introduction. Unicode doesn't really encode | |
129 | languages, but the writing systems for them--their scripts; and one | |
130 | script can be used by many languages. Unicode also encodes things that | |
131 | aren't really about languages, such as symbols like C<BAGGAGE CLAIM>.) | |
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132 | |
133 | The Unicode code points are just abstract numbers. To input and | |
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134 | output these abstract numbers, the numbers must be I<encoded> or |
135 | I<serialised> somehow. Unicode defines several I<character encoding | |
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136 | forms>, of which I<UTF-8> is the most popular. UTF-8 is a |
137 | variable length encoding that encodes Unicode characters as 1 to 4 | |
e1b711da | 138 | bytes. Other encodings |
4c496f0c | 139 | include UTF-16 and UTF-32 and their big- and little-endian variants |
f321be7e | 140 | (UTF-8 is byte-order independent). The ISO/IEC 10646 defines the UCS-2 |
4c496f0c | 141 | and UCS-4 encoding forms. |
ba62762e | 142 | |
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143 | For more information about encodings--for instance, to learn what |
144 | I<surrogates> and I<byte order marks> (BOMs) are--see L<perlunicode>. | |
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145 | |
146 | =head2 Perl's Unicode Support | |
147 | ||
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148 | Starting from Perl v5.6.0, Perl has had the capacity to handle Unicode |
149 | natively. Perl v5.8.0, however, is the first recommended release for | |
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150 | serious Unicode work. The maintenance release 5.6.1 fixed many of the |
151 | problems of the initial Unicode implementation, but for example | |
1bfb14c4 | 152 | regular expressions still do not work with Unicode in 5.6.1. |
c2fb32ed | 153 | Perl v5.14.0 is the first release where Unicode support is |
c8695642 | 154 | (almost) seamlessly integrable without some gotchas (the exception being |
91a927c1 | 155 | some differences in L<quotemeta|perlfunc/quotemeta>, and that is fixed |
2e2b2571 | 156 | starting in Perl 5.16.0). To enable this |
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157 | seamless support, you should C<use feature 'unicode_strings'> (which is |
158 | automatically selected if you C<use 5.012> or higher). See L<feature>. | |
159 | (5.14 also fixes a number of bugs and departures from the Unicode | |
160 | standard.) | |
161 | ||
c2fb32ed | 162 | Before Perl v5.8.0, the use of C<use utf8> was used to declare |
ba62762e | 163 | that operations in the current block or file would be Unicode-aware. |
376d9008 | 164 | This model was found to be wrong, or at least clumsy: the "Unicodeness" |
1bfb14c4 | 165 | is now carried with the data, instead of being attached to the |
c8695642 | 166 | operations. |
c2fb32ed | 167 | Starting with Perl v5.8.0, only one case remains where an explicit C<use |
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168 | utf8> is needed: if your Perl script itself is encoded in UTF-8, you can |
169 | use UTF-8 in your identifier names, and in string and regular expression | |
376d9008 | 170 | literals, by saying C<use utf8>. This is not the default because |
8f8cf39c | 171 | scripts with legacy 8-bit data in them would break. See L<utf8>. |
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172 | |
173 | =head2 Perl's Unicode Model | |
174 | ||
376d9008 | 175 | Perl supports both pre-5.6 strings of eight-bit native bytes, and |
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176 | strings of Unicode characters. The general principle is that Perl tries |
177 | to keep its data as eight-bit bytes for as long as possible, but as soon | |
178 | as Unicodeness cannot be avoided, the data is transparently upgraded | |
c2fb32ed | 179 | to Unicode. Prior to Perl v5.14.0, the upgrade was not completely |
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180 | transparent (see L<perlunicode/The "Unicode Bug">), and for backwards |
181 | compatibility, full transparency is not gained unless C<use feature | |
182 | 'unicode_strings'> (see L<feature>) or C<use 5.012> (or higher) is | |
183 | selected. | |
ba62762e | 184 | |
4192de81 | 185 | Internally, Perl currently uses either whatever the native eight-bit |
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186 | character set of the platform (for example Latin-1) is, defaulting to |
187 | UTF-8, to encode Unicode strings. Specifically, if all code points in | |
188 | the string are C<0xFF> or less, Perl uses the native eight-bit | |
189 | character set. Otherwise, it uses UTF-8. | |
4192de81 | 190 | |
7ca610e8 | 191 | A user of Perl does not normally need to know nor care how Perl |
20ba30f4 | 192 | happens to encode its internal strings, but it becomes relevant when |
ac036724 | 193 | outputting Unicode strings to a stream without a PerlIO layer (one with |
194 | the "default" encoding). In such a case, the raw bytes used internally | |
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195 | (the native character set or UTF-8, as appropriate for each string) |
196 | will be used, and a "Wide character" warning will be issued if those | |
197 | strings contain a character beyond 0x00FF. | |
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198 | |
199 | For example, | |
200 | ||
ae5648b3 | 201 | perl -e 'print "\x{DF}\n", "\x{0100}\x{DF}\n"' |
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202 | |
203 | produces a fairly useless mixture of native bytes and UTF-8, as well | |
1bfb14c4 | 204 | as a warning: |
4192de81 | 205 | |
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206 | Wide character in print at ... |
207 | ||
740d4bb2 | 208 | To output UTF-8, use the C<:encoding> or C<:utf8> output layer. Prepending |
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209 | |
210 | binmode(STDOUT, ":utf8"); | |
211 | ||
376d9008 | 212 | to this sample program ensures that the output is completely UTF-8, |
1bfb14c4 | 213 | and removes the program's warning. |
ba62762e | 214 | |
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215 | You can enable automatic UTF-8-ification of your standard file |
216 | handles, default C<open()> layer, and C<@ARGV> by using either | |
217 | the C<-C> command line switch or the C<PERL_UNICODE> environment | |
218 | variable, see L<perlrun> for the documentation of the C<-C> switch. | |
219 | ||
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220 | Note that this means that Perl expects other software to work the same |
221 | way: | |
8aa8f774 | 222 | if Perl has been led to believe that STDIN should be UTF-8, but then |
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223 | STDIN coming in from another command is not UTF-8, Perl will likely |
224 | complain about the malformed UTF-8. | |
b310b053 | 225 | |
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226 | All features that combine Unicode and I/O also require using the new |
227 | PerlIO feature. Almost all Perl 5.8 platforms do use PerlIO, though: | |
228 | you can see whether yours is by running "perl -V" and looking for | |
229 | C<useperlio=define>. | |
230 | ||
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231 | =head2 Unicode and EBCDIC |
232 | ||
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233 | Perl 5.8.0 added support for Unicode on EBCDIC platforms. This support |
234 | was allowed to lapse in later releases, but was revived in 5.22. | |
235 | Unicode support is somewhat more complex to implement since additional | |
236 | conversions are needed. See L<perlebcdic> for more information. | |
64c66fb6 | 237 | |
64c66fb6 | 238 | On EBCDIC platforms, the internal Unicode encoding form is UTF-EBCDIC |
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239 | instead of UTF-8. The difference is that as UTF-8 is "ASCII-safe" in |
240 | that ASCII characters encode to UTF-8 as-is, while UTF-EBCDIC is | |
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241 | "EBCDIC-safe", in that all the basic characters (which includes all |
242 | those that have ASCII equivalents (like C<"A">, C<"0">, C<"%">, I<etc.>) | |
243 | are the same in both EBCDIC and UTF-EBCDIC. Often, documentation | |
244 | will use the term "UTF-8" to mean UTF-EBCDIC as well. This is the case | |
245 | in this document. | |
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246 | |
247 | =head2 Creating Unicode | |
248 | ||
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249 | This section applies fully to Perls starting with v5.22. Various |
250 | caveats for earlier releases are in the L</Earlier releases caveats> | |
251 | subsection below. | |
ba62762e | 252 | |
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253 | To create Unicode characters in literals, |
254 | use the C<\N{...}> notation in double-quoted strings: | |
ba62762e | 255 | |
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256 | my $smiley_from_name = "\N{WHITE SMILING FACE}"; |
257 | my $smiley_from_code_point = "\N{U+263a}"; | |
ba62762e | 258 | |
0145df7d | 259 | Similarly, they can be used in regular expression literals |
ba62762e | 260 | |
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261 | $smiley =~ /\N{WHITE SMILING FACE}/; |
262 | $smiley =~ /\N{U+263a}/; | |
ba62762e | 263 | |
0145df7d | 264 | At run-time you can use: |
ba62762e | 265 | |
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266 | use charnames (); |
267 | my $hebrew_alef_from_name | |
268 | = charnames::string_vianame("HEBREW LETTER ALEF"); | |
269 | my $hebrew_alef_from_code_point = charnames::string_vianame("U+05D0"); | |
ba62762e | 270 | |
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271 | Naturally, C<ord()> will do the reverse: it turns a character into |
272 | a code point. | |
ba62762e | 273 | |
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274 | There are other runtime options as well. You can use C<pack()>: |
275 | ||
276 | my $hebrew_alef_from_code_point = pack("U", 0x05d0); | |
277 | ||
278 | Or you can use C<chr()>, though it is less convenient in the general | |
279 | case: | |
280 | ||
281 | $hebrew_alef_from_code_point = chr(utf8::unicode_to_native(0x05d0)); | |
282 | utf8::upgrade($hebrew_alef_from_code_point); | |
283 | ||
284 | The C<utf8::unicode_to_native()> and C<utf8::upgrade()> aren't needed if | |
285 | the argument is above 0xFF, so the above could have been written as | |
286 | ||
287 | $hebrew_alef_from_code_point = chr(0x05d0); | |
ba62762e | 288 | |
0145df7d | 289 | since 0x5d0 is above 255. |
ba62762e | 290 | |
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291 | C<\x{}> and C<\o{}> can also be used to specify code points at compile |
292 | time in double-quotish strings, but, for backward compatibility with | |
293 | older Perls, the same rules apply as with C<chr()> for code points less | |
294 | than 256. | |
ba62762e | 295 | |
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296 | C<utf8::unicode_to_native()> is used so that the Perl code is portable |
297 | to EBCDIC platforms. You can omit it if you're I<really> sure no one | |
298 | will ever want to use your code on a non-ASCII platform. Starting in | |
299 | Perl v5.22, calls to it on ASCII platforms are optimized out, so there's | |
300 | no performance penalty at all in adding it. Or you can simply use the | |
301 | other constructs that don't require it. | |
ba62762e | 302 | |
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303 | See L</"Further Resources"> for how to find all these names and numeric |
304 | codes. | |
ba62762e | 305 | |
0145df7d | 306 | =head3 Earlier releases caveats |
8a5e5dd5 | 307 | |
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308 | On EBCDIC platforms, prior to v5.22, using C<\N{U+...}> doesn't work |
309 | properly. | |
1eda90df | 310 | |
0145df7d KW |
311 | Prior to v5.16, using C<\N{...}> with a character name (as opposed to a |
312 | C<U+...> code point) required a S<C<use charnames :full>>. | |
771cd3b2 | 313 | |
0145df7d KW |
314 | Prior to v5.14, there were some bugs in C<\N{...}> with a character name |
315 | (as opposed to a C<U+...> code point). | |
316 | ||
317 | C<charnames::string_vianame()> was introduced in v5.14. Prior to that, | |
318 | C<charnames::vianame()> should work, but only if the argument is of the | |
319 | form C<"U+...">. Your best bet there for runtime Unicode by character | |
320 | name is probably: | |
321 | ||
322 | use charnames (); | |
323 | my $hebrew_alef_from_name | |
324 | = pack("U", charnames::vianame("HEBREW LETTER ALEF")); | |
1eda90df | 325 | |
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326 | =head2 Handling Unicode |
327 | ||
328 | Handling Unicode is for the most part transparent: just use the | |
329 | strings as usual. Functions like C<index()>, C<length()>, and | |
330 | C<substr()> will work on the Unicode characters; regular expressions | |
331 | will work on the Unicode characters (see L<perlunicode> and L<perlretut>). | |
332 | ||
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333 | Note that Perl considers grapheme clusters to be separate characters, so for |
334 | example | |
ba62762e | 335 | |
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336 | print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), |
337 | "\n"; | |
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338 | |
339 | will print 2, not 1. The only exception is that regular expressions | |
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340 | have C<\X> for matching an extended grapheme cluster. (Thus C<\X> in a |
341 | regular expression would match the entire sequence of both the example | |
342 | characters.) | |
ba62762e | 343 | |
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344 | Life is not quite so transparent, however, when working with legacy |
345 | encodings, I/O, and certain special cases: | |
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346 | |
347 | =head2 Legacy Encodings | |
348 | ||
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349 | When you combine legacy data and Unicode, the legacy data needs |
350 | to be upgraded to Unicode. Normally the legacy data is assumed to be | |
351 | ISO 8859-1 (or EBCDIC, if applicable). | |
ba62762e | 352 | |
376d9008 | 353 | The C<Encode> module knows about many encodings and has interfaces |
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354 | for doing conversions between those encodings: |
355 | ||
2c9359a2 RGS |
356 | use Encode 'decode'; |
357 | $data = decode("iso-8859-3", $data); # convert from legacy to utf-8 | |
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358 | |
359 | =head2 Unicode I/O | |
360 | ||
8baee566 | 361 | Normally, writing out Unicode data |
ba62762e | 362 | |
8baee566 | 363 | print FH $some_string_with_unicode, "\n"; |
ba62762e | 364 | |
8baee566 | 365 | produces raw bytes that Perl happens to use to internally encode the |
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366 | Unicode string. Perl's internal encoding depends on the system as |
367 | well as what characters happen to be in the string at the time. If | |
368 | any of the characters are at code points C<0x100> or above, you will get | |
369 | a warning. To ensure that the output is explicitly rendered in the | |
370 | encoding you desire--and to avoid the warning--open the stream with | |
371 | the desired encoding. Some examples: | |
ba62762e | 372 | |
ec90690f TS |
373 | open FH, ">:utf8", "file"; |
374 | ||
375 | open FH, ">:encoding(ucs2)", "file"; | |
376 | open FH, ">:encoding(UTF-8)", "file"; | |
377 | open FH, ">:encoding(shift_jis)", "file"; | |
1d7919c5 | 378 | |
376d9008 | 379 | and on already open streams, use C<binmode()>: |
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380 | |
381 | binmode(STDOUT, ":utf8"); | |
382 | ||
ec90690f TS |
383 | binmode(STDOUT, ":encoding(ucs2)"); |
384 | binmode(STDOUT, ":encoding(UTF-8)"); | |
385 | binmode(STDOUT, ":encoding(shift_jis)"); | |
386 | ||
b5d8778e | 387 | The matching of encoding names is loose: case does not matter, and |
fae2c0fb | 388 | many encodings have several aliases. Note that the C<:utf8> layer |
1bfb14c4 | 389 | must always be specified exactly like that; it is I<not> subject to |
c8695642 | 390 | the loose matching of encoding names. Also note that currently C<:utf8> is unsafe for |
740d4bb2 | 391 | input, because it accepts the data without validating that it is indeed valid |
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392 | UTF-8; you should instead use C<:encoding(utf-8)> (with or without a |
393 | hyphen). | |
b5d8778e | 394 | |
376d9008 JB |
395 | See L<PerlIO> for the C<:utf8> layer, L<PerlIO::encoding> and |
396 | L<Encode::PerlIO> for the C<:encoding()> layer, and | |
397 | L<Encode::Supported> for many encodings supported by the C<Encode> | |
398 | module. | |
ba62762e | 399 | |
a5f0baef | 400 | Reading in a file that you know happens to be encoded in one of the |
1bfb14c4 JH |
401 | Unicode or legacy encodings does not magically turn the data into |
402 | Unicode in Perl's eyes. To do that, specify the appropriate | |
fae2c0fb | 403 | layer when opening files |
ba62762e | 404 | |
740d4bb2 | 405 | open(my $fh,'<:encoding(utf8)', 'anything'); |
8baee566 JF |
406 | my $line_of_unicode = <$fh>; |
407 | ||
ec90690f | 408 | open(my $fh,'<:encoding(Big5)', 'anything'); |
8baee566 | 409 | my $line_of_unicode = <$fh>; |
ba62762e | 410 | |
fae2c0fb | 411 | The I/O layers can also be specified more flexibly with |
376d9008 | 412 | the C<open> pragma. See L<open>, or look at the following example. |
ba62762e | 413 | |
9e5bbba0 KW |
414 | use open ':encoding(utf8)'; # input/output default encoding will be |
415 | # UTF-8 | |
1d7919c5 JH |
416 | open X, ">file"; |
417 | print X chr(0x100), "\n"; | |
ba62762e | 418 | close X; |
1d7919c5 | 419 | open Y, "<file"; |
ba62762e JH |
420 | printf "%#x\n", ord(<Y>); # this should print 0x100 |
421 | close Y; | |
422 | ||
fae2c0fb | 423 | With the C<open> pragma you can use the C<:locale> layer |
ba62762e | 424 | |
12f98225 | 425 | BEGIN { $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R' } |
9e5bbba0 KW |
426 | # the :locale will probe the locale environment variables like |
427 | # LC_ALL | |
ba62762e JH |
428 | use open OUT => ':locale'; # russki parusski |
429 | open(O, ">koi8"); | |
430 | print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1 | |
431 | close O; | |
432 | open(I, "<koi8"); | |
433 | printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1 | |
434 | close I; | |
435 | ||
8baee566 JF |
436 | These methods install a transparent filter on the I/O stream that |
437 | converts data from the specified encoding when it is read in from the | |
a5f0baef | 438 | stream. The result is always Unicode. |
ba62762e JH |
439 | |
440 | The L<open> pragma affects all the C<open()> calls after the pragma by | |
fae2c0fb RGS |
441 | setting default layers. If you want to affect only certain |
442 | streams, use explicit layers directly in the C<open()> call. | |
ba62762e JH |
443 | |
444 | You can switch encodings on an already opened stream by using | |
8baee566 | 445 | C<binmode()>; see L<perlfunc/binmode>. |
ba62762e | 446 | |
c2fb32ed | 447 | The C<:locale> does not currently work with |
1ecefa54 | 448 | C<open()> and C<binmode()>, only with the C<open> pragma. The |
8baee566 | 449 | C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>, |
1ecefa54 | 450 | C<binmode()>, and the C<open> pragma. |
ba62762e | 451 | |
fae2c0fb | 452 | Similarly, you may use these I/O layers on output streams to |
a5f0baef JH |
453 | automatically convert Unicode to the specified encoding when it is |
454 | written to the stream. For example, the following snippet copies the | |
455 | contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to | |
456 | the file "text.utf8", encoded as UTF-8: | |
ba62762e | 457 | |
c722ef0a JH |
458 | open(my $nihongo, '<:encoding(iso-2022-jp)', 'text.jis'); |
459 | open(my $unicode, '>:utf8', 'text.utf8'); | |
0cf8a8d9 | 460 | while (<$nihongo>) { print $unicode $_ } |
ba62762e JH |
461 | |
462 | The naming of encodings, both by the C<open()> and by the C<open> | |
2575c402 JW |
463 | pragma allows for flexible names: C<koi8-r> and C<KOI8R> will both be |
464 | understood. | |
ba62762e JH |
465 | |
466 | Common encodings recognized by ISO, MIME, IANA, and various other | |
8baee566 | 467 | standardisation organisations are recognised; for a more detailed |
1bfb14c4 | 468 | list see L<Encode::Supported>. |
ba62762e JH |
469 | |
470 | C<read()> reads characters and returns the number of characters. | |
471 | C<seek()> and C<tell()> operate on byte counts, as do C<sysread()> | |
472 | and C<sysseek()>. | |
473 | ||
8baee566 | 474 | Notice that because of the default behaviour of not doing any |
fae2c0fb | 475 | conversion upon input if there is no default layer, |
ba62762e | 476 | it is easy to mistakenly write code that keeps on expanding a file |
1bfb14c4 | 477 | by repeatedly encoding the data: |
ba62762e JH |
478 | |
479 | # BAD CODE WARNING | |
480 | open F, "file"; | |
8baee566 | 481 | local $/; ## read in the whole file of 8-bit characters |
ba62762e JH |
482 | $t = <F>; |
483 | close F; | |
740d4bb2 | 484 | open F, ">:encoding(utf8)", "file"; |
8baee566 | 485 | print F $t; ## convert to UTF-8 on output |
ba62762e JH |
486 | close F; |
487 | ||
488 | If you run this code twice, the contents of the F<file> will be twice | |
740d4bb2 JW |
489 | UTF-8 encoded. A C<use open ':encoding(utf8)'> would have avoided the |
490 | bug, or explicitly opening also the F<file> for input as UTF-8. | |
ba62762e | 491 | |
0c901d84 | 492 | B<NOTE>: the C<:utf8> and C<:encoding> features work only if your |
cdf6c183 TH |
493 | Perl has been built with L<PerlIO>, which is the default |
494 | on most systems. | |
0c901d84 | 495 | |
1ecefa54 JH |
496 | =head2 Displaying Unicode As Text |
497 | ||
498 | Sometimes you might want to display Perl scalars containing Unicode as | |
8baee566 | 499 | simple ASCII (or EBCDIC) text. The following subroutine converts |
1ecefa54 | 500 | its argument so that Unicode characters with code points greater than |
1bfb14c4 JH |
501 | 255 are displayed as C<\x{...}>, control characters (like C<\n>) are |
502 | displayed as C<\x..>, and the rest of the characters as themselves: | |
1ecefa54 | 503 | |
9e5bbba0 | 504 | sub nice_string { |
96cfa1df KW |
505 | join("", |
506 | map { $_ > 255 # if wide character... | |
507 | ? sprintf("\\x{%04X}", $_) # \x{...} | |
508 | : chr($_) =~ /[[:cntrl:]]/ # else if control character... | |
509 | ? sprintf("\\x%02X", $_) # \x.. | |
510 | : quotemeta(chr($_)) # else quoted or as themselves | |
511 | } unpack("W*", $_[0])); # unpack Unicode characters | |
58c274a1 JF |
512 | } |
513 | ||
514 | For example, | |
515 | ||
516 | nice_string("foo\x{100}bar\n") | |
517 | ||
d0551e73 | 518 | returns the string |
58c274a1 | 519 | |
d0551e73 JH |
520 | 'foo\x{0100}bar\x0A' |
521 | ||
522 | which is ready to be printed. | |
1ecefa54 | 523 | |
0145df7d KW |
524 | (C<\\x{}> is used here instead of C<\\N{}>, since it's most likely that |
525 | you want to see what the native values are.) | |
526 | ||
ba62762e JH |
527 | =head2 Special Cases |
528 | ||
529 | =over 4 | |
530 | ||
531 | =item * | |
532 | ||
533 | Bit Complement Operator ~ And vec() | |
534 | ||
1bfb14c4 JH |
535 | The bit complement operator C<~> may produce surprising results if |
536 | used on strings containing characters with ordinal values above | |
537 | 255. In such a case, the results are consistent with the internal | |
538 | encoding of the characters, but not with much else. So don't do | |
539 | that. Similarly for C<vec()>: you will be operating on the | |
540 | internally-encoded bit patterns of the Unicode characters, not on | |
541 | the code point values, which is very probably not what you want. | |
ba62762e JH |
542 | |
543 | =item * | |
544 | ||
8baee566 JF |
545 | Peeking At Perl's Internal Encoding |
546 | ||
547 | Normal users of Perl should never care how Perl encodes any particular | |
a5f0baef | 548 | Unicode string (because the normal ways to get at the contents of a |
376d9008 | 549 | string with Unicode--via input and output--should always be via |
fae2c0fb | 550 | explicitly-defined I/O layers). But if you must, there are two |
a5f0baef | 551 | ways of looking behind the scenes. |
ba62762e JH |
552 | |
553 | One way of peeking inside the internal encoding of Unicode characters | |
f337b084 TH |
554 | is to use C<unpack("C*", ...> to get the bytes of whatever the string |
555 | encoding happens to be, or C<unpack("U0..", ...)> to get the bytes of the | |
556 | UTF-8 encoding: | |
ba62762e | 557 | |
8baee566 | 558 | # this prints c4 80 for the UTF-8 bytes 0xc4 0x80 |
f337b084 | 559 | print join(" ", unpack("U0(H2)*", pack("U", 0x100))), "\n"; |
ba62762e JH |
560 | |
561 | Yet another way would be to use the Devel::Peek module: | |
562 | ||
563 | perl -MDevel::Peek -e 'Dump(chr(0x100))' | |
564 | ||
1e54db1a | 565 | That shows the C<UTF8> flag in FLAGS and both the UTF-8 bytes |
376d9008 | 566 | and Unicode characters in C<PV>. See also later in this document |
8800c35a | 567 | the discussion about the C<utf8::is_utf8()> function. |
ba62762e JH |
568 | |
569 | =back | |
570 | ||
571 | =head2 Advanced Topics | |
572 | ||
573 | =over 4 | |
574 | ||
575 | =item * | |
576 | ||
577 | String Equivalence | |
578 | ||
579 | The question of string equivalence turns somewhat complicated | |
376d9008 | 580 | in Unicode: what do you mean by "equal"? |
ba62762e | 581 | |
07698885 RGS |
582 | (Is C<LATIN CAPITAL LETTER A WITH ACUTE> equal to |
583 | C<LATIN CAPITAL LETTER A>?) | |
ba62762e | 584 | |
a5f0baef JH |
585 | The short answer is that by default Perl compares equivalence (C<eq>, |
586 | C<ne>) based only on code points of the characters. In the above | |
376d9008 | 587 | case, the answer is no (because 0x00C1 != 0x0041). But sometimes, any |
c8695642 | 588 | CAPITAL LETTER A's should be considered equal, or even A's of any case. |
ba62762e JH |
589 | |
590 | The long answer is that you need to consider character normalization | |
e1b711da KW |
591 | and casing issues: see L<Unicode::Normalize>, Unicode Technical Report #15, |
592 | L<Unicode Normalization Forms|http://www.unicode.org/unicode/reports/tr15> and | |
593 | sections on case mapping in the L<Unicode Standard|http://www.unicode.org>. | |
ba62762e | 594 | |
1bfb14c4 | 595 | As of Perl 5.8.0, the "Full" case-folding of I<Case |
afba1538 | 596 | Mappings/SpecialCasing> is implemented, but bugs remain in C<qr//i> with them, |
4d2d7a4c | 597 | mostly fixed by 5.14, and essentially entirely by 5.18. |
ba62762e JH |
598 | |
599 | =item * | |
600 | ||
601 | String Collation | |
602 | ||
376d9008 | 603 | People like to see their strings nicely sorted--or as Unicode |
ba62762e JH |
604 | parlance goes, collated. But again, what do you mean by collate? |
605 | ||
07698885 RGS |
606 | (Does C<LATIN CAPITAL LETTER A WITH ACUTE> come before or after |
607 | C<LATIN CAPITAL LETTER A WITH GRAVE>?) | |
ba62762e | 608 | |
58c274a1 | 609 | The short answer is that by default, Perl compares strings (C<lt>, |
ba62762e | 610 | C<le>, C<cmp>, C<ge>, C<gt>) based only on the code points of the |
1bfb14c4 | 611 | characters. In the above case, the answer is "after", since |
da76a1f4 | 612 | C<0x00C1> > C<0x00C0>. |
ba62762e JH |
613 | |
614 | The long answer is that "it depends", and a good answer cannot be | |
615 | given without knowing (at the very least) the language context. | |
616 | See L<Unicode::Collate>, and I<Unicode Collation Algorithm> | |
2bbc8d55 | 617 | L<http://www.unicode.org/unicode/reports/tr10/> |
ba62762e JH |
618 | |
619 | =back | |
620 | ||
621 | =head2 Miscellaneous | |
622 | ||
623 | =over 4 | |
624 | ||
625 | =item * | |
626 | ||
3ff56b75 | 627 | Character Ranges and Classes |
ba62762e | 628 | |
0eb9ada1 KW |
629 | Character ranges in regular expression bracketed character classes ( e.g., |
630 | C</[a-z]/>) and in the C<tr///> (also known as C<y///>) operator are not | |
631 | magically Unicode-aware. What this means is that C<[A-Za-z]> will not | |
632 | magically start to mean "all alphabetic letters" (not that it does mean that | |
633 | even for 8-bit characters; for those, if you are using locales (L<perllocale>), | |
634 | use C</[[:alpha:]]/>; and if not, use the 8-bit-aware property C<\p{alpha}>). | |
635 | ||
636 | All the properties that begin with C<\p> (and its inverse C<\P>) are actually | |
637 | character classes that are Unicode-aware. There are dozens of them, see | |
638 | L<perluniprops>. | |
639 | ||
0145df7d | 640 | Starting in v5.22, you can use Unicode code points as the end points of |
74fe8880 KW |
641 | regular expression pattern character ranges, and the range will include |
642 | all Unicode code points that lie between those end points, inclusive. | |
0145df7d KW |
643 | |
644 | qr/ [\N{U+03]-\N{U+20}] /x | |
645 | ||
646 | includes the code points | |
647 | C<\N{U+03}>, C<\N{U+04}>, ..., C<\N{U+20}>. | |
ba62762e | 648 | |
74fe8880 KW |
649 | (It is planned to extend this behavior to ranges in C<tr///> in Perl |
650 | v5.24.) | |
651 | ||
ba62762e JH |
652 | =item * |
653 | ||
654 | String-To-Number Conversions | |
655 | ||
376d9008 JB |
656 | Unicode does define several other decimal--and numeric--characters |
657 | besides the familiar 0 to 9, such as the Arabic and Indic digits. | |
ba62762e | 658 | Perl does not support string-to-number conversion for digits other |
4d2d7a4c | 659 | than ASCII C<0> to C<9> (and ASCII C<a> to C<f> for hexadecimal). |
c8695642 | 660 | To get safe conversions from any Unicode string, use |
67592e11 | 661 | L<Unicode::UCD/num()>. |
ba62762e JH |
662 | |
663 | =back | |
664 | ||
665 | =head2 Questions With Answers | |
666 | ||
667 | =over 4 | |
668 | ||
818c4caa | 669 | =item * |
5cb3728c RB |
670 | |
671 | Will My Old Scripts Break? | |
ba62762e JH |
672 | |
673 | Very probably not. Unless you are generating Unicode characters | |
1bfb14c4 JH |
674 | somehow, old behaviour should be preserved. About the only behaviour |
675 | that has changed and which could start generating Unicode is the old | |
676 | behaviour of C<chr()> where supplying an argument more than 255 | |
677 | produced a character modulo 255. C<chr(300)>, for example, was equal | |
678 | to C<chr(45)> or "-" (in ASCII), now it is LATIN CAPITAL LETTER I WITH | |
679 | BREVE. | |
ba62762e | 680 | |
818c4caa | 681 | =item * |
5cb3728c RB |
682 | |
683 | How Do I Make My Scripts Work With Unicode? | |
ba62762e JH |
684 | |
685 | Very little work should be needed since nothing changes until you | |
1bfb14c4 JH |
686 | generate Unicode data. The most important thing is getting input as |
687 | Unicode; for that, see the earlier I/O discussion. | |
c8695642 KW |
688 | To get full seamless Unicode support, add |
689 | C<use feature 'unicode_strings'> (or C<use 5.012> or higher) to your | |
690 | script. | |
ba62762e | 691 | |
818c4caa | 692 | =item * |
5cb3728c RB |
693 | |
694 | How Do I Know Whether My String Is In Unicode? | |
ba62762e | 695 | |
c8695642 KW |
696 | You shouldn't have to care. But you may if your Perl is before 5.14.0 |
697 | or you haven't specified C<use feature 'unicode_strings'> or C<use | |
52d1f2c9 | 698 | 5.012> (or higher) because otherwise the rules for the code points |
c8695642 | 699 | in the range 128 to 255 are different depending on |
2bbc8d55 | 700 | whether the string they are contained within is in Unicode or not. |
e1b711da | 701 | (See L<perlunicode/When Unicode Does Not Happen>.) |
ba62762e | 702 | |
2bbc8d55 | 703 | To determine if a string is in Unicode, use: |
ba62762e | 704 | |
8800c35a | 705 | print utf8::is_utf8($string) ? 1 : 0, "\n"; |
ba62762e JH |
706 | |
707 | But note that this doesn't mean that any of the characters in the | |
708 | string are necessary UTF-8 encoded, or that any of the characters have | |
709 | code points greater than 0xFF (255) or even 0x80 (128), or that the | |
710 | string has any characters at all. All the C<is_utf8()> does is to | |
711 | return the value of the internal "utf8ness" flag attached to the | |
376d9008 | 712 | C<$string>. If the flag is off, the bytes in the scalar are interpreted |
3c1c8017 | 713 | as a single byte encoding. If the flag is on, the bytes in the scalar |
0eb9ada1 KW |
714 | are interpreted as the (variable-length, potentially multi-byte) UTF-8 encoded |
715 | code points of the characters. Bytes added to a UTF-8 encoded string are | |
1e54db1a | 716 | automatically upgraded to UTF-8. If mixed non-UTF-8 and UTF-8 scalars |
c8695642 | 717 | are merged (double-quoted interpolation, explicit concatenation, or |
3c1c8017 AT |
718 | printf/sprintf parameter substitution), the result will be UTF-8 encoded |
719 | as if copies of the byte strings were upgraded to UTF-8: for example, | |
720 | ||
721 | $a = "ab\x80c"; | |
722 | $b = "\x{100}"; | |
723 | print "$a = $b\n"; | |
724 | ||
a02b5feb JH |
725 | the output string will be UTF-8-encoded C<ab\x80c = \x{100}\n>, but |
726 | C<$a> will stay byte-encoded. | |
ba62762e JH |
727 | |
728 | Sometimes you might really need to know the byte length of a string | |
ce7675db | 729 | instead of the character length. For that use either the |
00d823b9 | 730 | C<Encode::encode_utf8()> function or the C<bytes> pragma |
c8695642 | 731 | and the C<length()> function: |
ba62762e JH |
732 | |
733 | my $unicode = chr(0x100); | |
734 | print length($unicode), "\n"; # will print 1 | |
ce7675db | 735 | require Encode; |
9ba22424 | 736 | print length(Encode::encode_utf8($unicode)),"\n"; # will print 2 |
00d823b9 | 737 | use bytes; |
1bfb14c4 JH |
738 | print length($unicode), "\n"; # will also print 2 |
739 | # (the 0xC4 0x80 of the UTF-8) | |
0eb9ada1 | 740 | no bytes; |
ba62762e | 741 | |
818c4caa | 742 | =item * |
5cb3728c | 743 | |
c8695642 KW |
744 | How Do I Find Out What Encoding a File Has? |
745 | ||
968ee499 | 746 | You might try L<Encode::Guess>, but it has a number of limitations. |
c8695642 KW |
747 | |
748 | =item * | |
749 | ||
5cb3728c | 750 | How Do I Detect Data That's Not Valid In a Particular Encoding? |
ba62762e | 751 | |
8baee566 JF |
752 | Use the C<Encode> package to try converting it. |
753 | For example, | |
ba62762e | 754 | |
bb2f379c | 755 | use Encode 'decode_utf8'; |
2bbc8d55 | 756 | |
228ee848 | 757 | if (eval { decode_utf8($string, Encode::FB_CROAK); 1 }) { |
a365f2ce | 758 | # $string is valid utf8 |
ba62762e | 759 | } else { |
a365f2ce | 760 | # $string is not valid utf8 |
ba62762e JH |
761 | } |
762 | ||
f337b084 | 763 | Or use C<unpack> to try decoding it: |
ba62762e JH |
764 | |
765 | use warnings; | |
f337b084 | 766 | @chars = unpack("C0U*", $string_of_bytes_that_I_think_is_utf8); |
ba62762e | 767 | |
ae5648b3 RGS |
768 | If invalid, a C<Malformed UTF-8 character> warning is produced. The "C0" means |
769 | "process the string character per character". Without that, the | |
770 | C<unpack("U*", ...)> would work in C<U0> mode (the default if the format | |
771 | string starts with C<U>) and it would return the bytes making up the UTF-8 | |
f337b084 | 772 | encoding of the target string, something that will always work. |
ba62762e | 773 | |
818c4caa | 774 | =item * |
5cb3728c RB |
775 | |
776 | How Do I Convert Binary Data Into a Particular Encoding, Or Vice Versa? | |
ba62762e | 777 | |
8baee566 JF |
778 | This probably isn't as useful as you might think. |
779 | Normally, you shouldn't need to. | |
ba62762e | 780 | |
1bfb14c4 | 781 | In one sense, what you are asking doesn't make much sense: encodings |
376d9008 | 782 | are for characters, and binary data are not "characters", so converting |
a5f0baef JH |
783 | "data" into some encoding isn't meaningful unless you know in what |
784 | character set and encoding the binary data is in, in which case it's | |
376d9008 | 785 | not just binary data, now is it? |
8baee566 | 786 | |
1bfb14c4 JH |
787 | If you have a raw sequence of bytes that you know should be |
788 | interpreted via a particular encoding, you can use C<Encode>: | |
ba62762e JH |
789 | |
790 | use Encode 'from_to'; | |
791 | from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8 | |
792 | ||
1bfb14c4 JH |
793 | The call to C<from_to()> changes the bytes in C<$data>, but nothing |
794 | material about the nature of the string has changed as far as Perl is | |
795 | concerned. Both before and after the call, the string C<$data> | |
796 | contains just a bunch of 8-bit bytes. As far as Perl is concerned, | |
797 | the encoding of the string remains as "system-native 8-bit bytes". | |
8baee566 JF |
798 | |
799 | You might relate this to a fictional 'Translate' module: | |
800 | ||
801 | use Translate; | |
802 | my $phrase = "Yes"; | |
803 | Translate::from_to($phrase, 'english', 'deutsch'); | |
804 | ## phrase now contains "Ja" | |
ba62762e | 805 | |
8baee566 | 806 | The contents of the string changes, but not the nature of the string. |
1bfb14c4 JH |
807 | Perl doesn't know any more after the call than before that the |
808 | contents of the string indicates the affirmative. | |
ba62762e | 809 | |
376d9008 | 810 | Back to converting data. If you have (or want) data in your system's |
a5f0baef JH |
811 | native 8-bit encoding (e.g. Latin-1, EBCDIC, etc.), you can use |
812 | pack/unpack to convert to/from Unicode. | |
ba62762e | 813 | |
f337b084 TH |
814 | $native_string = pack("W*", unpack("U*", $Unicode_string)); |
815 | $Unicode_string = pack("U*", unpack("W*", $native_string)); | |
ba62762e JH |
816 | |
817 | If you have a sequence of bytes you B<know> is valid UTF-8, | |
818 | but Perl doesn't know it yet, you can make Perl a believer, too: | |
819 | ||
820 | use Encode 'decode_utf8'; | |
8baee566 | 821 | $Unicode = decode_utf8($bytes); |
ba62762e | 822 | |
f337b084 TH |
823 | or: |
824 | ||
825 | $Unicode = pack("U0a*", $bytes); | |
ae5648b3 | 826 | |
2bbc8d55 SP |
827 | You can find the bytes that make up a UTF-8 sequence with |
828 | ||
9e5bbba0 | 829 | @bytes = unpack("C*", $Unicode_string) |
2bbc8d55 SP |
830 | |
831 | and you can create well-formed Unicode with | |
832 | ||
9e5bbba0 | 833 | $Unicode_string = pack("U*", 0xff, ...) |
ba62762e | 834 | |
818c4caa | 835 | =item * |
5cb3728c RB |
836 | |
837 | How Do I Display Unicode? How Do I Input Unicode? | |
ba62762e | 838 | |
2bbc8d55 SP |
839 | See L<http://www.alanwood.net/unicode/> and |
840 | L<http://www.cl.cam.ac.uk/~mgk25/unicode.html> | |
ba62762e | 841 | |
818c4caa | 842 | =item * |
5cb3728c RB |
843 | |
844 | How Does Unicode Work With Traditional Locales? | |
ba62762e | 845 | |
31f05a37 KW |
846 | If your locale is a UTF-8 locale, starting in Perl v5.20, Perl works |
847 | well for all categories except C<LC_COLLATE> dealing with sorting and | |
848 | the C<cmp> operator. | |
849 | ||
850 | For other locales, starting in Perl 5.16, you can specify | |
66cbab2c KW |
851 | |
852 | use locale ':not_characters'; | |
853 | ||
31f05a37 | 854 | to get Perl to work well with them. The catch is that you |
66cbab2c KW |
855 | have to translate from the locale character set to/from Unicode |
856 | yourself. See L</Unicode IE<sol>O> above for how to | |
857 | ||
858 | use open ':locale'; | |
859 | ||
860 | to accomplish this, but full details are in L<perllocale/Unicode and | |
30189633 | 861 | UTF-8>, including gotchas that happen if you don't specify |
66cbab2c | 862 | C<:not_characters>. |
ba62762e JH |
863 | |
864 | =back | |
865 | ||
866 | =head2 Hexadecimal Notation | |
867 | ||
376d9008 JB |
868 | The Unicode standard prefers using hexadecimal notation because |
869 | that more clearly shows the division of Unicode into blocks of 256 characters. | |
ba62762e JH |
870 | Hexadecimal is also simply shorter than decimal. You can use decimal |
871 | notation, too, but learning to use hexadecimal just makes life easier | |
1bfb14c4 | 872 | with the Unicode standard. The C<U+HHHH> notation uses hexadecimal, |
076d825e | 873 | for example. |
ba62762e JH |
874 | |
875 | The C<0x> prefix means a hexadecimal number, the digits are 0-9 I<and> | |
876 | a-f (or A-F, case doesn't matter). Each hexadecimal digit represents | |
877 | four bits, or half a byte. C<print 0x..., "\n"> will show a | |
878 | hexadecimal number in decimal, and C<printf "%x\n", $decimal> will | |
879 | show a decimal number in hexadecimal. If you have just the | |
376d9008 | 880 | "hex digits" of a hexadecimal number, you can use the C<hex()> function. |
ba62762e JH |
881 | |
882 | print 0x0009, "\n"; # 9 | |
883 | print 0x000a, "\n"; # 10 | |
884 | print 0x000f, "\n"; # 15 | |
885 | print 0x0010, "\n"; # 16 | |
886 | print 0x0011, "\n"; # 17 | |
887 | print 0x0100, "\n"; # 256 | |
888 | ||
889 | print 0x0041, "\n"; # 65 | |
890 | ||
891 | printf "%x\n", 65; # 41 | |
892 | printf "%#x\n", 65; # 0x41 | |
893 | ||
894 | print hex("41"), "\n"; # 65 | |
895 | ||
896 | =head2 Further Resources | |
897 | ||
898 | =over 4 | |
899 | ||
900 | =item * | |
901 | ||
902 | Unicode Consortium | |
903 | ||
2bbc8d55 | 904 | L<http://www.unicode.org/> |
ba62762e JH |
905 | |
906 | =item * | |
907 | ||
908 | Unicode FAQ | |
909 | ||
2bbc8d55 | 910 | L<http://www.unicode.org/unicode/faq/> |
ba62762e JH |
911 | |
912 | =item * | |
913 | ||
914 | Unicode Glossary | |
915 | ||
2bbc8d55 | 916 | L<http://www.unicode.org/glossary/> |
ba62762e JH |
917 | |
918 | =item * | |
919 | ||
c8695642 KW |
920 | Unicode Recommended Reading List |
921 | ||
922 | The Unicode Consortium has a list of articles and books, some of which | |
923 | give a much more in depth treatment of Unicode: | |
924 | L<http://unicode.org/resources/readinglist.html> | |
925 | ||
926 | =item * | |
927 | ||
ba62762e JH |
928 | Unicode Useful Resources |
929 | ||
2bbc8d55 | 930 | L<http://www.unicode.org/unicode/onlinedat/resources.html> |
ba62762e JH |
931 | |
932 | =item * | |
933 | ||
934 | Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications | |
935 | ||
2bbc8d55 | 936 | L<http://www.alanwood.net/unicode/> |
ba62762e JH |
937 | |
938 | =item * | |
939 | ||
940 | UTF-8 and Unicode FAQ for Unix/Linux | |
941 | ||
2bbc8d55 | 942 | L<http://www.cl.cam.ac.uk/~mgk25/unicode.html> |
ba62762e JH |
943 | |
944 | =item * | |
945 | ||
946 | Legacy Character Sets | |
947 | ||
2bbc8d55 SP |
948 | L<http://www.czyborra.com/> |
949 | L<http://www.eki.ee/letter/> | |
ba62762e JH |
950 | |
951 | =item * | |
952 | ||
ba62762e JH |
953 | You can explore various information from the Unicode data files using |
954 | the C<Unicode::UCD> module. | |
955 | ||
956 | =back | |
957 | ||
f6edf83b JH |
958 | =head1 UNICODE IN OLDER PERLS |
959 | ||
960 | If you cannot upgrade your Perl to 5.8.0 or later, you can still | |
961 | do some Unicode processing by using the modules C<Unicode::String>, | |
962 | C<Unicode::Map8>, and C<Unicode::Map>, available from CPAN. | |
963 | If you have the GNU recode installed, you can also use the | |
376d9008 | 964 | Perl front-end C<Convert::Recode> for character conversions. |
f6edf83b | 965 | |
aaef10c5 | 966 | The following are fast conversions from ISO 8859-1 (Latin-1) bytes |
63de3cb2 | 967 | to UTF-8 bytes and back, the code works even with older Perl 5 versions. |
aaef10c5 JH |
968 | |
969 | # ISO 8859-1 to UTF-8 | |
970 | s/([\x80-\xFF])/chr(0xC0|ord($1)>>6).chr(0x80|ord($1)&0x3F)/eg; | |
971 | ||
972 | # UTF-8 to ISO 8859-1 | |
973 | s/([\xC2\xC3])([\x80-\xBF])/chr(ord($1)<<6&0xC0|ord($2)&0x3F)/eg; | |
974 | ||
ba62762e JH |
975 | =head1 SEE ALSO |
976 | ||
2575c402 | 977 | L<perlunitut>, L<perlunicode>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
4c496f0c JH |
978 | L<perlretut>, L<perlrun>, L<Unicode::Collate>, L<Unicode::Normalize>, |
979 | L<Unicode::UCD> | |
ba62762e | 980 | |
376d9008 | 981 | =head1 ACKNOWLEDGMENTS |
ba62762e JH |
982 | |
983 | Thanks to the kind readers of the perl5-porters@perl.org, | |
984 | perl-unicode@perl.org, linux-utf8@nl.linux.org, and unicore@unicode.org | |
985 | mailing lists for their valuable feedback. | |
986 | ||
987 | =head1 AUTHOR, COPYRIGHT, AND LICENSE | |
988 | ||
91a927c1 KW |
989 | Copyright 2001-2011 Jarkko Hietaniemi E<lt>jhi@iki.fiE<gt>. |
990 | Now maintained by Perl 5 Porters. | |
ba62762e JH |
991 | |
992 | This document may be distributed under the same terms as Perl itself. |