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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 |
20ae58f7 | 154 | (almost) seamlessly integrable without some gotchas. (There are a few |
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155 | exceptions. Firstly, some differences in L<quotemeta|perlfunc/quotemeta> |
156 | were fixed starting in Perl 5.16.0. Secondly, some differences in | |
157 | L<the range operator|perlop/Range Operators> were fixed starting in | |
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158 | Perl 5.26.0. Thirdly, some differences in L<split|perlfunc/split> were fixed |
159 | started in Perl 5.28.0.) | |
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160 | |
161 | To enable this | |
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162 | seamless support, you should C<use feature 'unicode_strings'> (which is |
163 | automatically selected if you C<use 5.012> or higher). See L<feature>. | |
164 | (5.14 also fixes a number of bugs and departures from the Unicode | |
165 | standard.) | |
166 | ||
c2fb32ed | 167 | Before Perl v5.8.0, the use of C<use utf8> was used to declare |
ba62762e | 168 | that operations in the current block or file would be Unicode-aware. |
376d9008 | 169 | This model was found to be wrong, or at least clumsy: the "Unicodeness" |
1bfb14c4 | 170 | is now carried with the data, instead of being attached to the |
c8695642 | 171 | operations. |
c2fb32ed | 172 | Starting with Perl v5.8.0, only one case remains where an explicit C<use |
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173 | utf8> is needed: if your Perl script itself is encoded in UTF-8, you can |
174 | use UTF-8 in your identifier names, and in string and regular expression | |
376d9008 | 175 | literals, by saying C<use utf8>. This is not the default because |
8f8cf39c | 176 | scripts with legacy 8-bit data in them would break. See L<utf8>. |
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177 | |
178 | =head2 Perl's Unicode Model | |
179 | ||
376d9008 | 180 | Perl supports both pre-5.6 strings of eight-bit native bytes, and |
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181 | strings of Unicode characters. The general principle is that Perl tries |
182 | to keep its data as eight-bit bytes for as long as possible, but as soon | |
183 | as Unicodeness cannot be avoided, the data is transparently upgraded | |
c2fb32ed | 184 | to Unicode. Prior to Perl v5.14.0, the upgrade was not completely |
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185 | transparent (see L<perlunicode/The "Unicode Bug">), and for backwards |
186 | compatibility, full transparency is not gained unless C<use feature | |
187 | 'unicode_strings'> (see L<feature>) or C<use 5.012> (or higher) is | |
188 | selected. | |
ba62762e | 189 | |
4192de81 | 190 | Internally, Perl currently uses either whatever the native eight-bit |
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191 | character set of the platform (for example Latin-1) is, defaulting to |
192 | UTF-8, to encode Unicode strings. Specifically, if all code points in | |
193 | the string are C<0xFF> or less, Perl uses the native eight-bit | |
194 | character set. Otherwise, it uses UTF-8. | |
4192de81 | 195 | |
7ca610e8 | 196 | A user of Perl does not normally need to know nor care how Perl |
20ba30f4 | 197 | happens to encode its internal strings, but it becomes relevant when |
ac036724 | 198 | outputting Unicode strings to a stream without a PerlIO layer (one with |
199 | the "default" encoding). In such a case, the raw bytes used internally | |
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200 | (the native character set or UTF-8, as appropriate for each string) |
201 | will be used, and a "Wide character" warning will be issued if those | |
202 | strings contain a character beyond 0x00FF. | |
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203 | |
204 | For example, | |
205 | ||
ae5648b3 | 206 | perl -e 'print "\x{DF}\n", "\x{0100}\x{DF}\n"' |
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207 | |
208 | produces a fairly useless mixture of native bytes and UTF-8, as well | |
1bfb14c4 | 209 | as a warning: |
4192de81 | 210 | |
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211 | Wide character in print at ... |
212 | ||
740d4bb2 | 213 | To output UTF-8, use the C<:encoding> or C<:utf8> output layer. Prepending |
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214 | |
215 | binmode(STDOUT, ":utf8"); | |
216 | ||
376d9008 | 217 | to this sample program ensures that the output is completely UTF-8, |
1bfb14c4 | 218 | and removes the program's warning. |
ba62762e | 219 | |
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220 | You can enable automatic UTF-8-ification of your standard file |
221 | handles, default C<open()> layer, and C<@ARGV> by using either | |
222 | the C<-C> command line switch or the C<PERL_UNICODE> environment | |
223 | variable, see L<perlrun> for the documentation of the C<-C> switch. | |
224 | ||
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225 | Note that this means that Perl expects other software to work the same |
226 | way: | |
8aa8f774 | 227 | if Perl has been led to believe that STDIN should be UTF-8, but then |
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228 | STDIN coming in from another command is not UTF-8, Perl will likely |
229 | complain about the malformed UTF-8. | |
b310b053 | 230 | |
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231 | All features that combine Unicode and I/O also require using the new |
232 | PerlIO feature. Almost all Perl 5.8 platforms do use PerlIO, though: | |
233 | you can see whether yours is by running "perl -V" and looking for | |
234 | C<useperlio=define>. | |
235 | ||
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236 | =head2 Unicode and EBCDIC |
237 | ||
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238 | Perl 5.8.0 added support for Unicode on EBCDIC platforms. This support |
239 | was allowed to lapse in later releases, but was revived in 5.22. | |
240 | Unicode support is somewhat more complex to implement since additional | |
241 | conversions are needed. See L<perlebcdic> for more information. | |
64c66fb6 | 242 | |
64c66fb6 | 243 | On EBCDIC platforms, the internal Unicode encoding form is UTF-EBCDIC |
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244 | instead of UTF-8. The difference is that as UTF-8 is "ASCII-safe" in |
245 | that ASCII characters encode to UTF-8 as-is, while UTF-EBCDIC is | |
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246 | "EBCDIC-safe", in that all the basic characters (which includes all |
247 | those that have ASCII equivalents (like C<"A">, C<"0">, C<"%">, I<etc.>) | |
248 | are the same in both EBCDIC and UTF-EBCDIC. Often, documentation | |
249 | will use the term "UTF-8" to mean UTF-EBCDIC as well. This is the case | |
250 | in this document. | |
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251 | |
252 | =head2 Creating Unicode | |
253 | ||
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254 | This section applies fully to Perls starting with v5.22. Various |
255 | caveats for earlier releases are in the L</Earlier releases caveats> | |
256 | subsection below. | |
ba62762e | 257 | |
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258 | To create Unicode characters in literals, |
259 | use the C<\N{...}> notation in double-quoted strings: | |
ba62762e | 260 | |
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261 | my $smiley_from_name = "\N{WHITE SMILING FACE}"; |
262 | my $smiley_from_code_point = "\N{U+263a}"; | |
ba62762e | 263 | |
0145df7d | 264 | Similarly, they can be used in regular expression literals |
ba62762e | 265 | |
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266 | $smiley =~ /\N{WHITE SMILING FACE}/; |
267 | $smiley =~ /\N{U+263a}/; | |
ba62762e | 268 | |
0145df7d | 269 | At run-time you can use: |
ba62762e | 270 | |
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271 | use charnames (); |
272 | my $hebrew_alef_from_name | |
273 | = charnames::string_vianame("HEBREW LETTER ALEF"); | |
274 | my $hebrew_alef_from_code_point = charnames::string_vianame("U+05D0"); | |
ba62762e | 275 | |
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276 | Naturally, C<ord()> will do the reverse: it turns a character into |
277 | a code point. | |
ba62762e | 278 | |
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279 | There are other runtime options as well. You can use C<pack()>: |
280 | ||
281 | my $hebrew_alef_from_code_point = pack("U", 0x05d0); | |
282 | ||
283 | Or you can use C<chr()>, though it is less convenient in the general | |
284 | case: | |
285 | ||
286 | $hebrew_alef_from_code_point = chr(utf8::unicode_to_native(0x05d0)); | |
287 | utf8::upgrade($hebrew_alef_from_code_point); | |
288 | ||
289 | The C<utf8::unicode_to_native()> and C<utf8::upgrade()> aren't needed if | |
290 | the argument is above 0xFF, so the above could have been written as | |
291 | ||
292 | $hebrew_alef_from_code_point = chr(0x05d0); | |
ba62762e | 293 | |
0145df7d | 294 | since 0x5d0 is above 255. |
ba62762e | 295 | |
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296 | C<\x{}> and C<\o{}> can also be used to specify code points at compile |
297 | time in double-quotish strings, but, for backward compatibility with | |
298 | older Perls, the same rules apply as with C<chr()> for code points less | |
299 | than 256. | |
ba62762e | 300 | |
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301 | C<utf8::unicode_to_native()> is used so that the Perl code is portable |
302 | to EBCDIC platforms. You can omit it if you're I<really> sure no one | |
303 | will ever want to use your code on a non-ASCII platform. Starting in | |
304 | Perl v5.22, calls to it on ASCII platforms are optimized out, so there's | |
305 | no performance penalty at all in adding it. Or you can simply use the | |
306 | other constructs that don't require it. | |
ba62762e | 307 | |
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308 | See L</"Further Resources"> for how to find all these names and numeric |
309 | codes. | |
ba62762e | 310 | |
0145df7d | 311 | =head3 Earlier releases caveats |
8a5e5dd5 | 312 | |
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313 | On EBCDIC platforms, prior to v5.22, using C<\N{U+...}> doesn't work |
314 | properly. | |
1eda90df | 315 | |
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316 | Prior to v5.16, using C<\N{...}> with a character name (as opposed to a |
317 | C<U+...> code point) required a S<C<use charnames :full>>. | |
771cd3b2 | 318 | |
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319 | Prior to v5.14, there were some bugs in C<\N{...}> with a character name |
320 | (as opposed to a C<U+...> code point). | |
321 | ||
322 | C<charnames::string_vianame()> was introduced in v5.14. Prior to that, | |
323 | C<charnames::vianame()> should work, but only if the argument is of the | |
324 | form C<"U+...">. Your best bet there for runtime Unicode by character | |
325 | name is probably: | |
326 | ||
327 | use charnames (); | |
328 | my $hebrew_alef_from_name | |
329 | = pack("U", charnames::vianame("HEBREW LETTER ALEF")); | |
1eda90df | 330 | |
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331 | =head2 Handling Unicode |
332 | ||
333 | Handling Unicode is for the most part transparent: just use the | |
334 | strings as usual. Functions like C<index()>, C<length()>, and | |
335 | C<substr()> will work on the Unicode characters; regular expressions | |
336 | will work on the Unicode characters (see L<perlunicode> and L<perlretut>). | |
337 | ||
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338 | Note that Perl considers grapheme clusters to be separate characters, so for |
339 | example | |
ba62762e | 340 | |
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341 | print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), |
342 | "\n"; | |
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343 | |
344 | will print 2, not 1. The only exception is that regular expressions | |
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345 | have C<\X> for matching an extended grapheme cluster. (Thus C<\X> in a |
346 | regular expression would match the entire sequence of both the example | |
347 | characters.) | |
ba62762e | 348 | |
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349 | Life is not quite so transparent, however, when working with legacy |
350 | encodings, I/O, and certain special cases: | |
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351 | |
352 | =head2 Legacy Encodings | |
353 | ||
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354 | When you combine legacy data and Unicode, the legacy data needs |
355 | to be upgraded to Unicode. Normally the legacy data is assumed to be | |
356 | ISO 8859-1 (or EBCDIC, if applicable). | |
ba62762e | 357 | |
376d9008 | 358 | The C<Encode> module knows about many encodings and has interfaces |
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359 | for doing conversions between those encodings: |
360 | ||
2c9359a2 | 361 | use Encode 'decode'; |
2426b0d3 | 362 | $data = decode("iso-8859-3", $data); # convert from legacy |
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363 | |
364 | =head2 Unicode I/O | |
365 | ||
8baee566 | 366 | Normally, writing out Unicode data |
ba62762e | 367 | |
8baee566 | 368 | print FH $some_string_with_unicode, "\n"; |
ba62762e | 369 | |
8baee566 | 370 | produces raw bytes that Perl happens to use to internally encode the |
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371 | Unicode string. Perl's internal encoding depends on the system as |
372 | well as what characters happen to be in the string at the time. If | |
373 | any of the characters are at code points C<0x100> or above, you will get | |
374 | a warning. To ensure that the output is explicitly rendered in the | |
375 | encoding you desire--and to avoid the warning--open the stream with | |
376 | the desired encoding. Some examples: | |
ba62762e | 377 | |
ec90690f TS |
378 | open FH, ">:utf8", "file"; |
379 | ||
380 | open FH, ">:encoding(ucs2)", "file"; | |
381 | open FH, ">:encoding(UTF-8)", "file"; | |
382 | open FH, ">:encoding(shift_jis)", "file"; | |
1d7919c5 | 383 | |
376d9008 | 384 | and on already open streams, use C<binmode()>: |
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385 | |
386 | binmode(STDOUT, ":utf8"); | |
387 | ||
ec90690f TS |
388 | binmode(STDOUT, ":encoding(ucs2)"); |
389 | binmode(STDOUT, ":encoding(UTF-8)"); | |
390 | binmode(STDOUT, ":encoding(shift_jis)"); | |
391 | ||
b5d8778e | 392 | The matching of encoding names is loose: case does not matter, and |
fae2c0fb | 393 | many encodings have several aliases. Note that the C<:utf8> layer |
1bfb14c4 | 394 | must always be specified exactly like that; it is I<not> subject to |
c8695642 | 395 | the loose matching of encoding names. Also note that currently C<:utf8> is unsafe for |
740d4bb2 | 396 | input, because it accepts the data without validating that it is indeed valid |
f34228d6 | 397 | UTF-8; you should instead use C<:encoding(UTF-8)> (with or without a |
367b3305 | 398 | hyphen). |
b5d8778e | 399 | |
376d9008 JB |
400 | See L<PerlIO> for the C<:utf8> layer, L<PerlIO::encoding> and |
401 | L<Encode::PerlIO> for the C<:encoding()> layer, and | |
402 | L<Encode::Supported> for many encodings supported by the C<Encode> | |
403 | module. | |
ba62762e | 404 | |
a5f0baef | 405 | Reading in a file that you know happens to be encoded in one of the |
1bfb14c4 JH |
406 | Unicode or legacy encodings does not magically turn the data into |
407 | Unicode in Perl's eyes. To do that, specify the appropriate | |
fae2c0fb | 408 | layer when opening files |
ba62762e | 409 | |
6d8e7450 | 410 | open(my $fh,'<:encoding(UTF-8)', 'anything'); |
8baee566 JF |
411 | my $line_of_unicode = <$fh>; |
412 | ||
ec90690f | 413 | open(my $fh,'<:encoding(Big5)', 'anything'); |
8baee566 | 414 | my $line_of_unicode = <$fh>; |
ba62762e | 415 | |
fae2c0fb | 416 | The I/O layers can also be specified more flexibly with |
376d9008 | 417 | the C<open> pragma. See L<open>, or look at the following example. |
ba62762e | 418 | |
6d8e7450 P |
419 | use open ':encoding(UTF-8)'; # input/output default encoding will be |
420 | # UTF-8 | |
1d7919c5 JH |
421 | open X, ">file"; |
422 | print X chr(0x100), "\n"; | |
ba62762e | 423 | close X; |
1d7919c5 | 424 | open Y, "<file"; |
ba62762e JH |
425 | printf "%#x\n", ord(<Y>); # this should print 0x100 |
426 | close Y; | |
427 | ||
fae2c0fb | 428 | With the C<open> pragma you can use the C<:locale> layer |
ba62762e | 429 | |
12f98225 | 430 | BEGIN { $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R' } |
9e5bbba0 KW |
431 | # the :locale will probe the locale environment variables like |
432 | # LC_ALL | |
ba62762e JH |
433 | use open OUT => ':locale'; # russki parusski |
434 | open(O, ">koi8"); | |
435 | print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1 | |
436 | close O; | |
437 | open(I, "<koi8"); | |
438 | printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1 | |
439 | close I; | |
440 | ||
8baee566 JF |
441 | These methods install a transparent filter on the I/O stream that |
442 | converts data from the specified encoding when it is read in from the | |
a5f0baef | 443 | stream. The result is always Unicode. |
ba62762e JH |
444 | |
445 | The L<open> pragma affects all the C<open()> calls after the pragma by | |
fae2c0fb RGS |
446 | setting default layers. If you want to affect only certain |
447 | streams, use explicit layers directly in the C<open()> call. | |
ba62762e JH |
448 | |
449 | You can switch encodings on an already opened stream by using | |
8baee566 | 450 | C<binmode()>; see L<perlfunc/binmode>. |
ba62762e | 451 | |
c2fb32ed | 452 | The C<:locale> does not currently work with |
1ecefa54 | 453 | C<open()> and C<binmode()>, only with the C<open> pragma. The |
8baee566 | 454 | C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>, |
1ecefa54 | 455 | C<binmode()>, and the C<open> pragma. |
ba62762e | 456 | |
fae2c0fb | 457 | Similarly, you may use these I/O layers on output streams to |
a5f0baef JH |
458 | automatically convert Unicode to the specified encoding when it is |
459 | written to the stream. For example, the following snippet copies the | |
460 | contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to | |
461 | the file "text.utf8", encoded as UTF-8: | |
ba62762e | 462 | |
c722ef0a JH |
463 | open(my $nihongo, '<:encoding(iso-2022-jp)', 'text.jis'); |
464 | open(my $unicode, '>:utf8', 'text.utf8'); | |
0cf8a8d9 | 465 | while (<$nihongo>) { print $unicode $_ } |
ba62762e JH |
466 | |
467 | The naming of encodings, both by the C<open()> and by the C<open> | |
2575c402 JW |
468 | pragma allows for flexible names: C<koi8-r> and C<KOI8R> will both be |
469 | understood. | |
ba62762e JH |
470 | |
471 | Common encodings recognized by ISO, MIME, IANA, and various other | |
8baee566 | 472 | standardisation organisations are recognised; for a more detailed |
1bfb14c4 | 473 | list see L<Encode::Supported>. |
ba62762e JH |
474 | |
475 | C<read()> reads characters and returns the number of characters. | |
ee329aef TC |
476 | C<seek()> and C<tell()> operate on byte counts, as does C<sysseek()>. |
477 | ||
478 | C<sysread()> and C<syswrite()> should not be used on file handles with | |
479 | character encoding layers, they behave badly, and that behaviour has | |
480 | been deprecated since perl 5.24. | |
ba62762e | 481 | |
8baee566 | 482 | Notice that because of the default behaviour of not doing any |
fae2c0fb | 483 | conversion upon input if there is no default layer, |
ba62762e | 484 | it is easy to mistakenly write code that keeps on expanding a file |
1bfb14c4 | 485 | by repeatedly encoding the data: |
ba62762e JH |
486 | |
487 | # BAD CODE WARNING | |
488 | open F, "file"; | |
8baee566 | 489 | local $/; ## read in the whole file of 8-bit characters |
ba62762e JH |
490 | $t = <F>; |
491 | close F; | |
6d8e7450 | 492 | open F, ">:encoding(UTF-8)", "file"; |
8baee566 | 493 | print F $t; ## convert to UTF-8 on output |
ba62762e JH |
494 | close F; |
495 | ||
496 | If you run this code twice, the contents of the F<file> will be twice | |
6d8e7450 | 497 | UTF-8 encoded. A C<use open ':encoding(UTF-8)'> would have avoided the |
740d4bb2 | 498 | bug, or explicitly opening also the F<file> for input as UTF-8. |
ba62762e | 499 | |
0c901d84 | 500 | B<NOTE>: the C<:utf8> and C<:encoding> features work only if your |
cdf6c183 TH |
501 | Perl has been built with L<PerlIO>, which is the default |
502 | on most systems. | |
0c901d84 | 503 | |
1ecefa54 JH |
504 | =head2 Displaying Unicode As Text |
505 | ||
506 | Sometimes you might want to display Perl scalars containing Unicode as | |
8baee566 | 507 | simple ASCII (or EBCDIC) text. The following subroutine converts |
1ecefa54 | 508 | its argument so that Unicode characters with code points greater than |
1bfb14c4 JH |
509 | 255 are displayed as C<\x{...}>, control characters (like C<\n>) are |
510 | displayed as C<\x..>, and the rest of the characters as themselves: | |
1ecefa54 | 511 | |
9e5bbba0 | 512 | sub nice_string { |
96cfa1df KW |
513 | join("", |
514 | map { $_ > 255 # if wide character... | |
515 | ? sprintf("\\x{%04X}", $_) # \x{...} | |
516 | : chr($_) =~ /[[:cntrl:]]/ # else if control character... | |
517 | ? sprintf("\\x%02X", $_) # \x.. | |
518 | : quotemeta(chr($_)) # else quoted or as themselves | |
519 | } unpack("W*", $_[0])); # unpack Unicode characters | |
58c274a1 JF |
520 | } |
521 | ||
522 | For example, | |
523 | ||
524 | nice_string("foo\x{100}bar\n") | |
525 | ||
d0551e73 | 526 | returns the string |
58c274a1 | 527 | |
d0551e73 JH |
528 | 'foo\x{0100}bar\x0A' |
529 | ||
530 | which is ready to be printed. | |
1ecefa54 | 531 | |
0145df7d KW |
532 | (C<\\x{}> is used here instead of C<\\N{}>, since it's most likely that |
533 | you want to see what the native values are.) | |
534 | ||
ba62762e JH |
535 | =head2 Special Cases |
536 | ||
537 | =over 4 | |
538 | ||
539 | =item * | |
540 | ||
fac71630 KW |
541 | Starting in Perl 5.28, it is illegal for bit operators, like C<~>, to |
542 | operate on strings containing code points above 255. | |
ba62762e | 543 | |
fac71630 KW |
544 | =item * |
545 | ||
546 | The vec() function may produce surprising results if | |
1bfb14c4 JH |
547 | used on strings containing characters with ordinal values above |
548 | 255. In such a case, the results are consistent with the internal | |
549 | encoding of the characters, but not with much else. So don't do | |
fac71630 KW |
550 | that, and starting in Perl 5.28, a deprecation message is issued if you |
551 | do so, becoming illegal in Perl 5.32. | |
ba62762e JH |
552 | |
553 | =item * | |
554 | ||
8baee566 JF |
555 | Peeking At Perl's Internal Encoding |
556 | ||
557 | Normal users of Perl should never care how Perl encodes any particular | |
a5f0baef | 558 | Unicode string (because the normal ways to get at the contents of a |
376d9008 | 559 | string with Unicode--via input and output--should always be via |
fae2c0fb | 560 | explicitly-defined I/O layers). But if you must, there are two |
a5f0baef | 561 | ways of looking behind the scenes. |
ba62762e JH |
562 | |
563 | One way of peeking inside the internal encoding of Unicode characters | |
f337b084 TH |
564 | is to use C<unpack("C*", ...> to get the bytes of whatever the string |
565 | encoding happens to be, or C<unpack("U0..", ...)> to get the bytes of the | |
566 | UTF-8 encoding: | |
ba62762e | 567 | |
8baee566 | 568 | # this prints c4 80 for the UTF-8 bytes 0xc4 0x80 |
f337b084 | 569 | print join(" ", unpack("U0(H2)*", pack("U", 0x100))), "\n"; |
ba62762e JH |
570 | |
571 | Yet another way would be to use the Devel::Peek module: | |
572 | ||
573 | perl -MDevel::Peek -e 'Dump(chr(0x100))' | |
574 | ||
1e54db1a | 575 | That shows the C<UTF8> flag in FLAGS and both the UTF-8 bytes |
376d9008 | 576 | and Unicode characters in C<PV>. See also later in this document |
8800c35a | 577 | the discussion about the C<utf8::is_utf8()> function. |
ba62762e JH |
578 | |
579 | =back | |
580 | ||
581 | =head2 Advanced Topics | |
582 | ||
583 | =over 4 | |
584 | ||
585 | =item * | |
586 | ||
587 | String Equivalence | |
588 | ||
589 | The question of string equivalence turns somewhat complicated | |
376d9008 | 590 | in Unicode: what do you mean by "equal"? |
ba62762e | 591 | |
07698885 RGS |
592 | (Is C<LATIN CAPITAL LETTER A WITH ACUTE> equal to |
593 | C<LATIN CAPITAL LETTER A>?) | |
ba62762e | 594 | |
a5f0baef JH |
595 | The short answer is that by default Perl compares equivalence (C<eq>, |
596 | C<ne>) based only on code points of the characters. In the above | |
376d9008 | 597 | case, the answer is no (because 0x00C1 != 0x0041). But sometimes, any |
c8695642 | 598 | CAPITAL LETTER A's should be considered equal, or even A's of any case. |
ba62762e JH |
599 | |
600 | The long answer is that you need to consider character normalization | |
e1b711da KW |
601 | and casing issues: see L<Unicode::Normalize>, Unicode Technical Report #15, |
602 | L<Unicode Normalization Forms|http://www.unicode.org/unicode/reports/tr15> and | |
603 | sections on case mapping in the L<Unicode Standard|http://www.unicode.org>. | |
ba62762e | 604 | |
1bfb14c4 | 605 | As of Perl 5.8.0, the "Full" case-folding of I<Case |
afba1538 | 606 | Mappings/SpecialCasing> is implemented, but bugs remain in C<qr//i> with them, |
4d2d7a4c | 607 | mostly fixed by 5.14, and essentially entirely by 5.18. |
ba62762e JH |
608 | |
609 | =item * | |
610 | ||
611 | String Collation | |
612 | ||
376d9008 | 613 | People like to see their strings nicely sorted--or as Unicode |
ba62762e JH |
614 | parlance goes, collated. But again, what do you mean by collate? |
615 | ||
07698885 RGS |
616 | (Does C<LATIN CAPITAL LETTER A WITH ACUTE> come before or after |
617 | C<LATIN CAPITAL LETTER A WITH GRAVE>?) | |
ba62762e | 618 | |
58c274a1 | 619 | The short answer is that by default, Perl compares strings (C<lt>, |
ba62762e | 620 | C<le>, C<cmp>, C<ge>, C<gt>) based only on the code points of the |
1bfb14c4 | 621 | characters. In the above case, the answer is "after", since |
da76a1f4 | 622 | C<0x00C1> > C<0x00C0>. |
ba62762e JH |
623 | |
624 | The long answer is that "it depends", and a good answer cannot be | |
625 | given without knowing (at the very least) the language context. | |
626 | See L<Unicode::Collate>, and I<Unicode Collation Algorithm> | |
2bbc8d55 | 627 | L<http://www.unicode.org/unicode/reports/tr10/> |
ba62762e JH |
628 | |
629 | =back | |
630 | ||
631 | =head2 Miscellaneous | |
632 | ||
633 | =over 4 | |
634 | ||
635 | =item * | |
636 | ||
3ff56b75 | 637 | Character Ranges and Classes |
ba62762e | 638 | |
0eb9ada1 KW |
639 | Character ranges in regular expression bracketed character classes ( e.g., |
640 | C</[a-z]/>) and in the C<tr///> (also known as C<y///>) operator are not | |
641 | magically Unicode-aware. What this means is that C<[A-Za-z]> will not | |
642 | magically start to mean "all alphabetic letters" (not that it does mean that | |
643 | even for 8-bit characters; for those, if you are using locales (L<perllocale>), | |
644 | use C</[[:alpha:]]/>; and if not, use the 8-bit-aware property C<\p{alpha}>). | |
645 | ||
646 | All the properties that begin with C<\p> (and its inverse C<\P>) are actually | |
647 | character classes that are Unicode-aware. There are dozens of them, see | |
648 | L<perluniprops>. | |
649 | ||
0145df7d | 650 | Starting in v5.22, you can use Unicode code points as the end points of |
74fe8880 KW |
651 | regular expression pattern character ranges, and the range will include |
652 | all Unicode code points that lie between those end points, inclusive. | |
0145df7d | 653 | |
77c8f263 | 654 | qr/ [ \N{U+03} - \N{U+20} ] /xx |
0145df7d KW |
655 | |
656 | includes the code points | |
657 | C<\N{U+03}>, C<\N{U+04}>, ..., C<\N{U+20}>. | |
ba62762e | 658 | |
f3f4813b | 659 | This also works for ranges in C<tr///> starting in Perl v5.24. |
74fe8880 | 660 | |
ba62762e JH |
661 | =item * |
662 | ||
663 | String-To-Number Conversions | |
664 | ||
376d9008 JB |
665 | Unicode does define several other decimal--and numeric--characters |
666 | besides the familiar 0 to 9, such as the Arabic and Indic digits. | |
ba62762e | 667 | Perl does not support string-to-number conversion for digits other |
4d2d7a4c | 668 | than ASCII C<0> to C<9> (and ASCII C<a> to C<f> for hexadecimal). |
c8695642 | 669 | To get safe conversions from any Unicode string, use |
67592e11 | 670 | L<Unicode::UCD/num()>. |
ba62762e JH |
671 | |
672 | =back | |
673 | ||
674 | =head2 Questions With Answers | |
675 | ||
676 | =over 4 | |
677 | ||
818c4caa | 678 | =item * |
5cb3728c RB |
679 | |
680 | Will My Old Scripts Break? | |
ba62762e JH |
681 | |
682 | Very probably not. Unless you are generating Unicode characters | |
1bfb14c4 JH |
683 | somehow, old behaviour should be preserved. About the only behaviour |
684 | that has changed and which could start generating Unicode is the old | |
685 | behaviour of C<chr()> where supplying an argument more than 255 | |
686 | produced a character modulo 255. C<chr(300)>, for example, was equal | |
687 | to C<chr(45)> or "-" (in ASCII), now it is LATIN CAPITAL LETTER I WITH | |
688 | BREVE. | |
ba62762e | 689 | |
818c4caa | 690 | =item * |
5cb3728c RB |
691 | |
692 | How Do I Make My Scripts Work With Unicode? | |
ba62762e JH |
693 | |
694 | Very little work should be needed since nothing changes until you | |
1bfb14c4 JH |
695 | generate Unicode data. The most important thing is getting input as |
696 | Unicode; for that, see the earlier I/O discussion. | |
c8695642 KW |
697 | To get full seamless Unicode support, add |
698 | C<use feature 'unicode_strings'> (or C<use 5.012> or higher) to your | |
699 | script. | |
ba62762e | 700 | |
818c4caa | 701 | =item * |
5cb3728c RB |
702 | |
703 | How Do I Know Whether My String Is In Unicode? | |
ba62762e | 704 | |
c8695642 KW |
705 | You shouldn't have to care. But you may if your Perl is before 5.14.0 |
706 | or you haven't specified C<use feature 'unicode_strings'> or C<use | |
52d1f2c9 | 707 | 5.012> (or higher) because otherwise the rules for the code points |
c8695642 | 708 | in the range 128 to 255 are different depending on |
2bbc8d55 | 709 | whether the string they are contained within is in Unicode or not. |
e1b711da | 710 | (See L<perlunicode/When Unicode Does Not Happen>.) |
ba62762e | 711 | |
2bbc8d55 | 712 | To determine if a string is in Unicode, use: |
ba62762e | 713 | |
8800c35a | 714 | print utf8::is_utf8($string) ? 1 : 0, "\n"; |
ba62762e JH |
715 | |
716 | But note that this doesn't mean that any of the characters in the | |
717 | string are necessary UTF-8 encoded, or that any of the characters have | |
718 | code points greater than 0xFF (255) or even 0x80 (128), or that the | |
719 | string has any characters at all. All the C<is_utf8()> does is to | |
720 | return the value of the internal "utf8ness" flag attached to the | |
376d9008 | 721 | C<$string>. If the flag is off, the bytes in the scalar are interpreted |
3c1c8017 | 722 | as a single byte encoding. If the flag is on, the bytes in the scalar |
0eb9ada1 KW |
723 | are interpreted as the (variable-length, potentially multi-byte) UTF-8 encoded |
724 | code points of the characters. Bytes added to a UTF-8 encoded string are | |
1e54db1a | 725 | automatically upgraded to UTF-8. If mixed non-UTF-8 and UTF-8 scalars |
c8695642 | 726 | are merged (double-quoted interpolation, explicit concatenation, or |
3c1c8017 AT |
727 | printf/sprintf parameter substitution), the result will be UTF-8 encoded |
728 | as if copies of the byte strings were upgraded to UTF-8: for example, | |
729 | ||
730 | $a = "ab\x80c"; | |
731 | $b = "\x{100}"; | |
732 | print "$a = $b\n"; | |
733 | ||
a02b5feb JH |
734 | the output string will be UTF-8-encoded C<ab\x80c = \x{100}\n>, but |
735 | C<$a> will stay byte-encoded. | |
ba62762e JH |
736 | |
737 | Sometimes you might really need to know the byte length of a string | |
96b10823 | 738 | instead of the character length. For that use the C<bytes> pragma |
c8695642 | 739 | and the C<length()> function: |
ba62762e JH |
740 | |
741 | my $unicode = chr(0x100); | |
742 | print length($unicode), "\n"; # will print 1 | |
00d823b9 | 743 | use bytes; |
96b10823 | 744 | print length($unicode), "\n"; # will print 2 |
1bfb14c4 | 745 | # (the 0xC4 0x80 of the UTF-8) |
0eb9ada1 | 746 | no bytes; |
ba62762e | 747 | |
818c4caa | 748 | =item * |
5cb3728c | 749 | |
c8695642 KW |
750 | How Do I Find Out What Encoding a File Has? |
751 | ||
968ee499 | 752 | You might try L<Encode::Guess>, but it has a number of limitations. |
c8695642 KW |
753 | |
754 | =item * | |
755 | ||
5cb3728c | 756 | How Do I Detect Data That's Not Valid In a Particular Encoding? |
ba62762e | 757 | |
8baee566 JF |
758 | Use the C<Encode> package to try converting it. |
759 | For example, | |
ba62762e | 760 | |
8e179dd8 | 761 | use Encode 'decode'; |
2bbc8d55 | 762 | |
8e179dd8 P |
763 | if (eval { decode('UTF-8', $string, Encode::FB_CROAK); 1 }) { |
764 | # $string is valid UTF-8 | |
ba62762e | 765 | } else { |
8e179dd8 | 766 | # $string is not valid UTF-8 |
ba62762e JH |
767 | } |
768 | ||
f337b084 | 769 | Or use C<unpack> to try decoding it: |
ba62762e JH |
770 | |
771 | use warnings; | |
f337b084 | 772 | @chars = unpack("C0U*", $string_of_bytes_that_I_think_is_utf8); |
ba62762e | 773 | |
ae5648b3 RGS |
774 | If invalid, a C<Malformed UTF-8 character> warning is produced. The "C0" means |
775 | "process the string character per character". Without that, the | |
776 | C<unpack("U*", ...)> would work in C<U0> mode (the default if the format | |
777 | string starts with C<U>) and it would return the bytes making up the UTF-8 | |
f337b084 | 778 | encoding of the target string, something that will always work. |
ba62762e | 779 | |
818c4caa | 780 | =item * |
5cb3728c RB |
781 | |
782 | How Do I Convert Binary Data Into a Particular Encoding, Or Vice Versa? | |
ba62762e | 783 | |
8baee566 JF |
784 | This probably isn't as useful as you might think. |
785 | Normally, you shouldn't need to. | |
ba62762e | 786 | |
1bfb14c4 | 787 | In one sense, what you are asking doesn't make much sense: encodings |
376d9008 | 788 | are for characters, and binary data are not "characters", so converting |
a5f0baef JH |
789 | "data" into some encoding isn't meaningful unless you know in what |
790 | character set and encoding the binary data is in, in which case it's | |
376d9008 | 791 | not just binary data, now is it? |
8baee566 | 792 | |
1bfb14c4 JH |
793 | If you have a raw sequence of bytes that you know should be |
794 | interpreted via a particular encoding, you can use C<Encode>: | |
ba62762e JH |
795 | |
796 | use Encode 'from_to'; | |
f34228d6 | 797 | from_to($data, "iso-8859-1", "UTF-8"); # from latin-1 to UTF-8 |
ba62762e | 798 | |
1bfb14c4 JH |
799 | The call to C<from_to()> changes the bytes in C<$data>, but nothing |
800 | material about the nature of the string has changed as far as Perl is | |
801 | concerned. Both before and after the call, the string C<$data> | |
802 | contains just a bunch of 8-bit bytes. As far as Perl is concerned, | |
803 | the encoding of the string remains as "system-native 8-bit bytes". | |
8baee566 JF |
804 | |
805 | You might relate this to a fictional 'Translate' module: | |
806 | ||
807 | use Translate; | |
808 | my $phrase = "Yes"; | |
809 | Translate::from_to($phrase, 'english', 'deutsch'); | |
810 | ## phrase now contains "Ja" | |
ba62762e | 811 | |
8baee566 | 812 | The contents of the string changes, but not the nature of the string. |
1bfb14c4 JH |
813 | Perl doesn't know any more after the call than before that the |
814 | contents of the string indicates the affirmative. | |
ba62762e | 815 | |
376d9008 | 816 | Back to converting data. If you have (or want) data in your system's |
a5f0baef JH |
817 | native 8-bit encoding (e.g. Latin-1, EBCDIC, etc.), you can use |
818 | pack/unpack to convert to/from Unicode. | |
ba62762e | 819 | |
f337b084 TH |
820 | $native_string = pack("W*", unpack("U*", $Unicode_string)); |
821 | $Unicode_string = pack("U*", unpack("W*", $native_string)); | |
ba62762e JH |
822 | |
823 | If you have a sequence of bytes you B<know> is valid UTF-8, | |
824 | but Perl doesn't know it yet, you can make Perl a believer, too: | |
825 | ||
016b3422 P |
826 | $Unicode = $bytes; |
827 | utf8::decode($Unicode); | |
ba62762e | 828 | |
f337b084 TH |
829 | or: |
830 | ||
831 | $Unicode = pack("U0a*", $bytes); | |
ae5648b3 | 832 | |
2bbc8d55 SP |
833 | You can find the bytes that make up a UTF-8 sequence with |
834 | ||
9e5bbba0 | 835 | @bytes = unpack("C*", $Unicode_string) |
2bbc8d55 SP |
836 | |
837 | and you can create well-formed Unicode with | |
838 | ||
9e5bbba0 | 839 | $Unicode_string = pack("U*", 0xff, ...) |
ba62762e | 840 | |
818c4caa | 841 | =item * |
5cb3728c RB |
842 | |
843 | How Do I Display Unicode? How Do I Input Unicode? | |
ba62762e | 844 | |
2bbc8d55 SP |
845 | See L<http://www.alanwood.net/unicode/> and |
846 | L<http://www.cl.cam.ac.uk/~mgk25/unicode.html> | |
ba62762e | 847 | |
818c4caa | 848 | =item * |
5cb3728c RB |
849 | |
850 | How Does Unicode Work With Traditional Locales? | |
ba62762e | 851 | |
725a67e5 KW |
852 | If your locale is a UTF-8 locale, starting in Perl v5.26, Perl works |
853 | well for all categories; before this, starting with Perl v5.20, it works | |
854 | for all categories but C<LC_COLLATE>, which deals with | |
855 | sorting and the C<cmp> operator. But note that the standard | |
856 | C<L<Unicode::Collate>> and C<L<Unicode::Collate::Locale>> modules offer | |
857 | much more powerful solutions to collation issues, and work on earlier | |
858 | releases. | |
31f05a37 KW |
859 | |
860 | For other locales, starting in Perl 5.16, you can specify | |
66cbab2c KW |
861 | |
862 | use locale ':not_characters'; | |
863 | ||
31f05a37 | 864 | to get Perl to work well with them. The catch is that you |
66cbab2c KW |
865 | have to translate from the locale character set to/from Unicode |
866 | yourself. See L</Unicode IE<sol>O> above for how to | |
867 | ||
868 | use open ':locale'; | |
869 | ||
870 | to accomplish this, but full details are in L<perllocale/Unicode and | |
30189633 | 871 | UTF-8>, including gotchas that happen if you don't specify |
66cbab2c | 872 | C<:not_characters>. |
ba62762e JH |
873 | |
874 | =back | |
875 | ||
876 | =head2 Hexadecimal Notation | |
877 | ||
376d9008 JB |
878 | The Unicode standard prefers using hexadecimal notation because |
879 | that more clearly shows the division of Unicode into blocks of 256 characters. | |
ba62762e JH |
880 | Hexadecimal is also simply shorter than decimal. You can use decimal |
881 | notation, too, but learning to use hexadecimal just makes life easier | |
1bfb14c4 | 882 | with the Unicode standard. The C<U+HHHH> notation uses hexadecimal, |
076d825e | 883 | for example. |
ba62762e JH |
884 | |
885 | The C<0x> prefix means a hexadecimal number, the digits are 0-9 I<and> | |
886 | a-f (or A-F, case doesn't matter). Each hexadecimal digit represents | |
887 | four bits, or half a byte. C<print 0x..., "\n"> will show a | |
888 | hexadecimal number in decimal, and C<printf "%x\n", $decimal> will | |
889 | show a decimal number in hexadecimal. If you have just the | |
376d9008 | 890 | "hex digits" of a hexadecimal number, you can use the C<hex()> function. |
ba62762e JH |
891 | |
892 | print 0x0009, "\n"; # 9 | |
893 | print 0x000a, "\n"; # 10 | |
894 | print 0x000f, "\n"; # 15 | |
895 | print 0x0010, "\n"; # 16 | |
896 | print 0x0011, "\n"; # 17 | |
897 | print 0x0100, "\n"; # 256 | |
898 | ||
899 | print 0x0041, "\n"; # 65 | |
900 | ||
901 | printf "%x\n", 65; # 41 | |
902 | printf "%#x\n", 65; # 0x41 | |
903 | ||
904 | print hex("41"), "\n"; # 65 | |
905 | ||
906 | =head2 Further Resources | |
907 | ||
908 | =over 4 | |
909 | ||
910 | =item * | |
911 | ||
912 | Unicode Consortium | |
913 | ||
2bbc8d55 | 914 | L<http://www.unicode.org/> |
ba62762e JH |
915 | |
916 | =item * | |
917 | ||
918 | Unicode FAQ | |
919 | ||
2bbc8d55 | 920 | L<http://www.unicode.org/unicode/faq/> |
ba62762e JH |
921 | |
922 | =item * | |
923 | ||
924 | Unicode Glossary | |
925 | ||
2bbc8d55 | 926 | L<http://www.unicode.org/glossary/> |
ba62762e JH |
927 | |
928 | =item * | |
929 | ||
c8695642 KW |
930 | Unicode Recommended Reading List |
931 | ||
932 | The Unicode Consortium has a list of articles and books, some of which | |
933 | give a much more in depth treatment of Unicode: | |
934 | L<http://unicode.org/resources/readinglist.html> | |
935 | ||
936 | =item * | |
937 | ||
ba62762e JH |
938 | Unicode Useful Resources |
939 | ||
2bbc8d55 | 940 | L<http://www.unicode.org/unicode/onlinedat/resources.html> |
ba62762e JH |
941 | |
942 | =item * | |
943 | ||
944 | Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications | |
945 | ||
2bbc8d55 | 946 | L<http://www.alanwood.net/unicode/> |
ba62762e JH |
947 | |
948 | =item * | |
949 | ||
950 | UTF-8 and Unicode FAQ for Unix/Linux | |
951 | ||
2bbc8d55 | 952 | L<http://www.cl.cam.ac.uk/~mgk25/unicode.html> |
ba62762e JH |
953 | |
954 | =item * | |
955 | ||
956 | Legacy Character Sets | |
957 | ||
2bbc8d55 SP |
958 | L<http://www.czyborra.com/> |
959 | L<http://www.eki.ee/letter/> | |
ba62762e JH |
960 | |
961 | =item * | |
962 | ||
ba62762e JH |
963 | You can explore various information from the Unicode data files using |
964 | the C<Unicode::UCD> module. | |
965 | ||
966 | =back | |
967 | ||
f6edf83b JH |
968 | =head1 UNICODE IN OLDER PERLS |
969 | ||
970 | If you cannot upgrade your Perl to 5.8.0 or later, you can still | |
971 | do some Unicode processing by using the modules C<Unicode::String>, | |
972 | C<Unicode::Map8>, and C<Unicode::Map>, available from CPAN. | |
973 | If you have the GNU recode installed, you can also use the | |
376d9008 | 974 | Perl front-end C<Convert::Recode> for character conversions. |
f6edf83b | 975 | |
aaef10c5 | 976 | The following are fast conversions from ISO 8859-1 (Latin-1) bytes |
63de3cb2 | 977 | to UTF-8 bytes and back, the code works even with older Perl 5 versions. |
aaef10c5 JH |
978 | |
979 | # ISO 8859-1 to UTF-8 | |
980 | s/([\x80-\xFF])/chr(0xC0|ord($1)>>6).chr(0x80|ord($1)&0x3F)/eg; | |
981 | ||
982 | # UTF-8 to ISO 8859-1 | |
983 | s/([\xC2\xC3])([\x80-\xBF])/chr(ord($1)<<6&0xC0|ord($2)&0x3F)/eg; | |
984 | ||
ba62762e JH |
985 | =head1 SEE ALSO |
986 | ||
2575c402 | 987 | L<perlunitut>, L<perlunicode>, L<Encode>, L<open>, L<utf8>, L<bytes>, |
4c496f0c JH |
988 | L<perlretut>, L<perlrun>, L<Unicode::Collate>, L<Unicode::Normalize>, |
989 | L<Unicode::UCD> | |
ba62762e | 990 | |
376d9008 | 991 | =head1 ACKNOWLEDGMENTS |
ba62762e JH |
992 | |
993 | Thanks to the kind readers of the perl5-porters@perl.org, | |
994 | perl-unicode@perl.org, linux-utf8@nl.linux.org, and unicore@unicode.org | |
995 | mailing lists for their valuable feedback. | |
996 | ||
997 | =head1 AUTHOR, COPYRIGHT, AND LICENSE | |
998 | ||
91a927c1 KW |
999 | Copyright 2001-2011 Jarkko Hietaniemi E<lt>jhi@iki.fiE<gt>. |
1000 | Now maintained by Perl 5 Porters. | |
ba62762e JH |
1001 | |
1002 | This document may be distributed under the same terms as Perl itself. |