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1 | =head1 NAME |
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2 | X<character class> |
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3 | |
4 | perlrecharclass - Perl Regular Expression Character Classes |
5 | |
6 | =head1 DESCRIPTION |
7 | |
8 | The top level documentation about Perl regular expressions |
9 | is found in L<perlre>. |
10 | |
11 | This manual page discusses the syntax and use of character |
12 | classes in Perl Regular Expressions. |
13 | |
14 | A character class is a way of denoting a set of characters, |
15 | in such a way that one character of the set is matched. |
16 | It's important to remember that matching a character class |
17 | consumes exactly one character in the source string. (The source |
18 | string is the string the regular expression is matched against.) |
19 | |
20 | There are three types of character classes in Perl regular |
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21 | expressions: the dot, backslashed sequences, and the form enclosed in square |
22 | brackets. Keep in mind, though, that often the term "character class" is used |
23 | to mean just the bracketed form. This is true in other Perl documentation. |
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24 | |
25 | =head2 The dot |
26 | |
27 | The dot (or period), C<.> is probably the most used, and certainly |
28 | the most well-known character class. By default, a dot matches any |
29 | character, except for the newline. The default can be changed to |
30 | add matching the newline with the I<single line> modifier: either |
31 | for the entire regular expression using the C</s> modifier, or |
32 | locally using C<(?s)>. |
33 | |
34 | Here are some examples: |
35 | |
36 | "a" =~ /./ # Match |
37 | "." =~ /./ # Match |
38 | "" =~ /./ # No match (dot has to match a character) |
39 | "\n" =~ /./ # No match (dot does not match a newline) |
40 | "\n" =~ /./s # Match (global 'single line' modifier) |
41 | "\n" =~ /(?s:.)/ # Match (local 'single line' modifier) |
42 | "ab" =~ /^.$/ # No match (dot matches one character) |
43 | |
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44 | =head2 Backslashed sequences |
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45 | X<\w> X<\W> X<\s> X<\S> X<\d> X<\D> X<\p> X<\P> |
46 | X<\N> X<\v> X<\V> X<\h> X<\H> |
47 | X<word> X<whitespace> |
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48 | |
49 | Perl regular expressions contain many backslashed sequences that |
50 | constitute a character class. That is, they will match a single |
51 | character, if that character belongs to a specific set of characters |
52 | (defined by the sequence). A backslashed sequence is a sequence of |
53 | characters starting with a backslash. Not all backslashed sequences |
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54 | are character classes; for a full list, see L<perlrebackslash>. |
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55 | |
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56 | Here's a list of the backslashed sequences that are character classes. They |
57 | are discussed in more detail below. |
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58 | |
59 | \d Match a digit character. |
60 | \D Match a non-digit character. |
61 | \w Match a "word" character. |
62 | \W Match a non-"word" character. |
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63 | \s Match a whitespace character. |
64 | \S Match a non-whitespace character. |
65 | \h Match a horizontal whitespace character. |
66 | \H Match a character that isn't horizontal whitespace. |
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67 | \N Match a character that isn't newline. Experimental. |
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68 | \v Match a vertical whitespace character. |
69 | \V Match a character that isn't vertical whitespace. |
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70 | \pP, \p{Prop} Match a character matching a Unicode property. |
71 | \PP, \P{Prop} Match a character that doesn't match a Unicode property. |
72 | |
73 | =head3 Digits |
74 | |
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75 | C<\d> matches a single character that is considered to be a I<digit>. What is |
76 | considered a digit depends on the internal encoding of the source string and |
77 | the locale that is in effect. If the source string is in UTF-8 format, C<\d> |
78 | not only matches the digits '0' - '9', but also Arabic, Devanagari and digits |
79 | from other languages. Otherwise, if there is a locale in effect, it will match |
80 | whatever characters the locale considers digits. Without a locale, C<\d> |
81 | matches the digits '0' to '9'. See L</Locale, EBCDIC, Unicode and UTF-8>. |
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82 | |
83 | Any character that isn't matched by C<\d> will be matched by C<\D>. |
84 | |
85 | =head3 Word characters |
86 | |
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87 | A C<\w> matches a single alphanumeric character (an alphabetic character, or a |
88 | decimal digit) or an underscore (C<_>), not a whole word. Use C<\w+> to match |
89 | a string of Perl-identifier characters (which isn't the same as matching an |
90 | English word). What is considered a word character depends on the internal |
91 | encoding of the string and the locale or EBCDIC code page that is in effect. If |
92 | it's in UTF-8 format, C<\w> matches those characters that are considered word |
93 | characters in the Unicode database. That is, it not only matches ASCII letters, |
94 | but also Thai letters, Greek letters, etc. If the source string isn't in UTF-8 |
95 | format, C<\w> matches those characters that are considered word characters by |
96 | the current locale or EBCDIC code page. Without a locale or EBCDIC code page, |
97 | C<\w> matches the ASCII letters, digits and the underscore. |
98 | See L</Locale, EBCDIC, Unicode and UTF-8>. |
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99 | |
100 | Any character that isn't matched by C<\w> will be matched by C<\W>. |
101 | |
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102 | =head3 Whitespace |
103 | |
104 | C<\s> matches any single character that is considered whitespace. In the ASCII |
105 | range, C<\s> matches the horizontal tab (C<\t>), the new line (C<\n>), the form |
106 | feed (C<\f>), the carriage return (C<\r>), and the space. (The vertical tab, |
107 | C<\cK> is not matched by C<\s>.) The exact set of characters matched by C<\s> |
108 | depends on whether the source string is in UTF-8 format and the locale or |
109 | EBCDIC code page that is in effect. If it's in UTF-8 format, C<\s> matches what |
110 | is considered whitespace in the Unicode database; the complete list is in the |
111 | table below. Otherwise, if there is a locale or EBCDIC code page in effect, |
112 | C<\s> matches whatever is considered whitespace by the current locale or EBCDIC |
113 | code page. Without a locale or EBCDIC code page, C<\s> matches the five |
114 | characters mentioned in the beginning of this paragraph. Perhaps the most |
115 | notable possible surprise is that C<\s> matches a non-breaking space only if |
116 | the non-breaking space is in a UTF-8 encoded string or the locale or EBCDIC |
117 | code page that is in effect has that character. |
118 | See L</Locale, EBCDIC, Unicode and UTF-8>. |
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119 | |
120 | Any character that isn't matched by C<\s> will be matched by C<\S>. |
121 | |
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122 | C<\h> will match any character that is considered horizontal whitespace; |
123 | this includes the space and the tab characters and 17 other characters that are |
124 | listed in the table below. C<\H> will match any character |
125 | that is not considered horizontal whitespace. |
126 | |
127 | C<\N> is new in 5.12, and is experimental. It, like the dot, will match any |
128 | character that is not a newline. The difference is that C<\N> will not be |
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129 | influenced by the single line C</s> regular expression modifier. Note that |
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130 | there is a second meaning of C<\N> when of the form C<\N{...}>. This form is |
131 | for named characters. See L<charnames> for those. If C<\N> is followed by an |
132 | opening brace and something that is not a quantifier, perl will assume that a |
133 | character name is coming, and not this meaning of C<\N>. For example, C<\N{3}> |
134 | means to match 3 non-newlines; C<\N{5,}> means to match 5 or more non-newlines, |
135 | but C<\N{4F}> and C<\N{F4}> are not legal quantifiers, and will cause perl to |
136 | look for characters named C<4F> or C<F4>, respectively (and won't find them, |
137 | thus raising an error, unless they have been defined using custom names). |
138 | |
139 | C<\v> will match any character that is considered vertical whitespace; |
140 | this includes the carriage return and line feed characters (newline) plus 5 |
141 | other characters listed in the table below. |
142 | C<\V> will match any character that is not considered vertical whitespace. |
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143 | |
144 | C<\R> matches anything that can be considered a newline under Unicode |
145 | rules. It's not a character class, as it can match a multi-character |
146 | sequence. Therefore, it cannot be used inside a bracketed character |
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147 | class; use C<\v> instead (vertical whitespace). |
148 | Details are discussed in L<perlrebackslash>. |
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149 | |
150 | Note that unlike C<\s>, C<\d> and C<\w>, C<\h> and C<\v> always match |
151 | the same characters, regardless whether the source string is in UTF-8 |
152 | format or not. The set of characters they match is also not influenced |
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153 | by locale nor EBCDIC code page. |
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154 | |
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155 | One might think that C<\s> is equivalent to C<[\h\v]>. This is not true. The |
156 | vertical tab (C<"\x0b">) is not matched by C<\s>, it is however considered |
157 | vertical whitespace. Furthermore, if the source string is not in UTF-8 format, |
158 | and any locale or EBCDIC code page that is in effect doesn't include them, the |
159 | next line (C<"\x85">) and the no-break space (C<"\xA0">) characters are not |
160 | matched by C<\s>, but are by C<\v> and C<\h> respectively. If the source |
161 | string is in UTF-8 format, both the next line and the no-break space are |
162 | matched by C<\s>. |
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163 | |
164 | The following table is a complete listing of characters matched by |
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165 | C<\s>, C<\h> and C<\v> as of Unicode 5.2. |
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166 | |
167 | The first column gives the code point of the character (in hex format), |
168 | the second column gives the (Unicode) name. The third column indicates |
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169 | by which class(es) the character is matched (assuming no locale or EBCDIC code |
170 | page is in effect that changes the C<\s> matching). |
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171 | |
172 | 0x00009 CHARACTER TABULATION h s |
173 | 0x0000a LINE FEED (LF) vs |
174 | 0x0000b LINE TABULATION v |
175 | 0x0000c FORM FEED (FF) vs |
176 | 0x0000d CARRIAGE RETURN (CR) vs |
177 | 0x00020 SPACE h s |
178 | 0x00085 NEXT LINE (NEL) vs [1] |
179 | 0x000a0 NO-BREAK SPACE h s [1] |
180 | 0x01680 OGHAM SPACE MARK h s |
181 | 0x0180e MONGOLIAN VOWEL SEPARATOR h s |
182 | 0x02000 EN QUAD h s |
183 | 0x02001 EM QUAD h s |
184 | 0x02002 EN SPACE h s |
185 | 0x02003 EM SPACE h s |
186 | 0x02004 THREE-PER-EM SPACE h s |
187 | 0x02005 FOUR-PER-EM SPACE h s |
188 | 0x02006 SIX-PER-EM SPACE h s |
189 | 0x02007 FIGURE SPACE h s |
190 | 0x02008 PUNCTUATION SPACE h s |
191 | 0x02009 THIN SPACE h s |
192 | 0x0200a HAIR SPACE h s |
193 | 0x02028 LINE SEPARATOR vs |
194 | 0x02029 PARAGRAPH SEPARATOR vs |
195 | 0x0202f NARROW NO-BREAK SPACE h s |
196 | 0x0205f MEDIUM MATHEMATICAL SPACE h s |
197 | 0x03000 IDEOGRAPHIC SPACE h s |
198 | |
199 | =over 4 |
200 | |
201 | =item [1] |
202 | |
203 | NEXT LINE and NO-BREAK SPACE only match C<\s> if the source string is in |
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204 | UTF-8 format, or the locale or EBCDIC code page that is in effect includes them. |
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205 | |
206 | =back |
207 | |
208 | It is worth noting that C<\d>, C<\w>, etc, match single characters, not |
209 | complete numbers or words. To match a number (that consists of integers), |
210 | use C<\d+>; to match a word, use C<\w+>. |
211 | |
212 | |
213 | =head3 Unicode Properties |
214 | |
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215 | C<\pP> and C<\p{Prop}> are character classes to match characters that fit given |
216 | Unicode properties. One letter property names can be used in the C<\pP> form, |
217 | with the property name following the C<\p>, otherwise, braces are required. |
218 | When using braces, there is a single form, which is just the property name |
219 | enclosed in the braces, and a compound form which looks like C<\p{name=value}>, |
220 | which means to match if the property "name" for the character has the particular |
221 | "value". |
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222 | For instance, a match for a number can be written as C</\pN/> or as |
223 | C</\p{Number}/>, or as C</\p{Number=True}/>. |
224 | Lowercase letters are matched by the property I<Lowercase_Letter> which |
225 | has as short form I<Ll>. They need the braces, so are written as C</\p{Ll}/> or |
226 | C</\p{Lowercase_Letter}/>, or C</\p{General_Category=Lowercase_Letter}/> |
227 | (the underscores are optional). |
228 | C</\pLl/> is valid, but means something different. |
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229 | It matches a two character string: a letter (Unicode property C<\pL>), |
230 | followed by a lowercase C<l>. |
231 | |
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232 | For more details, see L<perlunicode/Unicode Character Properties>; for a |
233 | complete list of possible properties, see |
234 | L<perluniprops/Properties accessible through \p{} and \P{}>. |
235 | It is also possible to define your own properties. This is discussed in |
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236 | L<perlunicode/User-Defined Character Properties>. |
237 | |
238 | |
239 | =head4 Examples |
240 | |
241 | "a" =~ /\w/ # Match, "a" is a 'word' character. |
242 | "7" =~ /\w/ # Match, "7" is a 'word' character as well. |
243 | "a" =~ /\d/ # No match, "a" isn't a digit. |
244 | "7" =~ /\d/ # Match, "7" is a digit. |
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245 | " " =~ /\s/ # Match, a space is whitespace. |
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246 | "a" =~ /\D/ # Match, "a" is a non-digit. |
247 | "7" =~ /\D/ # No match, "7" is not a non-digit. |
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248 | " " =~ /\S/ # No match, a space is not non-whitespace. |
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249 | |
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250 | " " =~ /\h/ # Match, space is horizontal whitespace. |
251 | " " =~ /\v/ # No match, space is not vertical whitespace. |
252 | "\r" =~ /\v/ # Match, a return is vertical whitespace. |
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253 | |
254 | "a" =~ /\pL/ # Match, "a" is a letter. |
255 | "a" =~ /\p{Lu}/ # No match, /\p{Lu}/ matches upper case letters. |
256 | |
257 | "\x{0e0b}" =~ /\p{Thai}/ # Match, \x{0e0b} is the character |
258 | # 'THAI CHARACTER SO SO', and that's in |
259 | # Thai Unicode class. |
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260 | "a" =~ /\P{Lao}/ # Match, as "a" is not a Laotian character. |
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261 | |
262 | |
263 | =head2 Bracketed Character Classes |
264 | |
265 | The third form of character class you can use in Perl regular expressions |
266 | is the bracketed form. In its simplest form, it lists the characters |
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267 | that may be matched, surrounded by square brackets, like this: C<[aeiou]>. |
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268 | This matches one of C<a>, C<e>, C<i>, C<o> or C<u>. Like the other |
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269 | character classes, exactly one character will be matched. To match |
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270 | a longer string consisting of characters mentioned in the character |
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271 | class, follow the character class with a quantifier. For instance, |
272 | C<[aeiou]+> matches a string of one or more lowercase ASCII vowels. |
273 | |
274 | Repeating a character in a character class has no |
275 | effect; it's considered to be in the set only once. |
276 | |
277 | Examples: |
278 | |
279 | "e" =~ /[aeiou]/ # Match, as "e" is listed in the class. |
280 | "p" =~ /[aeiou]/ # No match, "p" is not listed in the class. |
281 | "ae" =~ /^[aeiou]$/ # No match, a character class only matches |
282 | # a single character. |
283 | "ae" =~ /^[aeiou]+$/ # Match, due to the quantifier. |
284 | |
285 | =head3 Special Characters Inside a Bracketed Character Class |
286 | |
287 | Most characters that are meta characters in regular expressions (that |
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288 | is, characters that carry a special meaning like C<.>, C<*>, or C<(>) lose |
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289 | their special meaning and can be used inside a character class without |
290 | the need to escape them. For instance, C<[()]> matches either an opening |
291 | parenthesis, or a closing parenthesis, and the parens inside the character |
292 | class don't group or capture. |
293 | |
294 | Characters that may carry a special meaning inside a character class are: |
295 | C<\>, C<^>, C<->, C<[> and C<]>, and are discussed below. They can be |
296 | escaped with a backslash, although this is sometimes not needed, in which |
297 | case the backslash may be omitted. |
298 | |
299 | The sequence C<\b> is special inside a bracketed character class. While |
300 | outside the character class C<\b> is an assertion indicating a point |
301 | that does not have either two word characters or two non-word characters |
302 | on either side, inside a bracketed character class, C<\b> matches a |
303 | backspace character. |
304 | |
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305 | The sequences |
306 | C<\a>, |
307 | C<\c>, |
308 | C<\e>, |
309 | C<\f>, |
310 | C<\n>, |
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311 | C<\N{I<NAME>}>, |
312 | C<\N{U+I<wide hex char>}>, |
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313 | C<\r>, |
314 | C<\t>, |
315 | and |
316 | C<\x> |
317 | are also special and have the same meanings as they do outside a bracketed character |
318 | class. |
319 | |
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320 | Also, a backslash followed by two or three octal digits is considered an octal |
321 | number. |
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322 | |
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323 | A C<[> is not special inside a character class, unless it's the start |
324 | of a POSIX character class (see below). It normally does not need escaping. |
325 | |
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326 | A C<]> is normally either the end of a POSIX character class (see below), or it |
327 | signals the end of the bracketed character class. If you want to include a |
328 | C<]> in the set of characters, you must generally escape it. |
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329 | However, if the C<]> is the I<first> (or the second if the first |
330 | character is a caret) character of a bracketed character class, it |
331 | does not denote the end of the class (as you cannot have an empty class) |
332 | and is considered part of the set of characters that can be matched without |
333 | escaping. |
334 | |
335 | Examples: |
336 | |
337 | "+" =~ /[+?*]/ # Match, "+" in a character class is not special. |
338 | "\cH" =~ /[\b]/ # Match, \b inside in a character class |
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339 | # is equivalent to a backspace. |
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340 | "]" =~ /[][]/ # Match, as the character class contains. |
341 | # both [ and ]. |
342 | "[]" =~ /[[]]/ # Match, the pattern contains a character class |
343 | # containing just ], and the character class is |
344 | # followed by a ]. |
345 | |
346 | =head3 Character Ranges |
347 | |
348 | It is not uncommon to want to match a range of characters. Luckily, instead |
349 | of listing all the characters in the range, one may use the hyphen (C<->). |
350 | If inside a bracketed character class you have two characters separated |
351 | by a hyphen, it's treated as if all the characters between the two are in |
352 | the class. For instance, C<[0-9]> matches any ASCII digit, and C<[a-m]> |
353 | matches any lowercase letter from the first half of the ASCII alphabet. |
354 | |
355 | Note that the two characters on either side of the hyphen are not |
356 | necessary both letters or both digits. Any character is possible, |
357 | although not advisable. C<['-?]> contains a range of characters, but |
358 | most people will not know which characters that will be. Furthermore, |
359 | such ranges may lead to portability problems if the code has to run on |
360 | a platform that uses a different character set, such as EBCDIC. |
361 | |
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362 | If a hyphen in a character class cannot syntactically be part of a range, for |
363 | instance because it is the first or the last character of the character class, |
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364 | or if it immediately follows a range, the hyphen isn't special, and will be |
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365 | considered a character that may be matched literally. You have to escape the |
366 | hyphen with a backslash if you want to have a hyphen in your set of characters |
367 | to be matched, and its position in the class is such that it could be |
368 | considered part of a range. |
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369 | |
370 | Examples: |
371 | |
372 | [a-z] # Matches a character that is a lower case ASCII letter. |
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373 | [a-fz] # Matches any letter between 'a' and 'f' (inclusive) or |
374 | # the letter 'z'. |
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375 | [-z] # Matches either a hyphen ('-') or the letter 'z'. |
376 | [a-f-m] # Matches any letter between 'a' and 'f' (inclusive), the |
377 | # hyphen ('-'), or the letter 'm'. |
378 | ['-?] # Matches any of the characters '()*+,-./0123456789:;<=>? |
379 | # (But not on an EBCDIC platform). |
380 | |
381 | |
382 | =head3 Negation |
383 | |
384 | It is also possible to instead list the characters you do not want to |
385 | match. You can do so by using a caret (C<^>) as the first character in the |
386 | character class. For instance, C<[^a-z]> matches a character that is not a |
387 | lowercase ASCII letter. |
388 | |
389 | This syntax make the caret a special character inside a bracketed character |
390 | class, but only if it is the first character of the class. So if you want |
391 | to have the caret as one of the characters you want to match, you either |
392 | have to escape the caret, or not list it first. |
393 | |
394 | Examples: |
395 | |
396 | "e" =~ /[^aeiou]/ # No match, the 'e' is listed. |
397 | "x" =~ /[^aeiou]/ # Match, as 'x' isn't a lowercase vowel. |
398 | "^" =~ /[^^]/ # No match, matches anything that isn't a caret. |
399 | "^" =~ /[x^]/ # Match, caret is not special here. |
400 | |
401 | =head3 Backslash Sequences |
402 | |
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403 | You can put any backslash sequence character class (with the exception of |
404 | C<\N>) inside a bracketed character class, and it will act just |
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405 | as if you put all the characters matched by the backslash sequence inside the |
406 | character class. For instance, C<[a-f\d]> will match any digit, or any of the |
407 | lowercase letters between 'a' and 'f' inclusive. |
408 | |
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409 | C<\N> within a bracketed character class must be of the forms C<\N{I<name>}> or |
410 | C<\N{U+I<wide hex char>}> for the same reason that a dot C<.> inside a |
411 | bracketed character class loses its special meaning: it matches nearly |
412 | anything, which generally isn't what you want to happen. |
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413 | |
414 | Examples: |
415 | |
416 | /[\p{Thai}\d]/ # Matches a character that is either a Thai |
417 | # character, or a digit. |
418 | /[^\p{Arabic}()]/ # Matches a character that is neither an Arabic |
419 | # character, nor a parenthesis. |
420 | |
421 | Backslash sequence character classes cannot form one of the endpoints |
422 | of a range. |
423 | |
424 | =head3 Posix Character Classes |
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425 | X<character class> X<\p> X<\p{}> |
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426 | X<alpha> X<alnum> X<ascii> X<blank> X<cntrl> X<digit> X<graph> |
427 | X<lower> X<print> X<punct> X<space> X<upper> X<word> X<xdigit> |
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428 | |
429 | Posix character classes have the form C<[:class:]>, where I<class> is |
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430 | name, and the C<[:> and C<:]> delimiters. Posix character classes only appear |
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431 | I<inside> bracketed character classes, and are a convenient and descriptive |
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432 | way of listing a group of characters, though they currently suffer from |
433 | portability issues (see below and L<Locale, EBCDIC, Unicode and UTF-8>). Be |
434 | careful about the syntax, |
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435 | |
436 | # Correct: |
437 | $string =~ /[[:alpha:]]/ |
438 | |
439 | # Incorrect (will warn): |
440 | $string =~ /[:alpha:]/ |
441 | |
442 | The latter pattern would be a character class consisting of a colon, |
443 | and the letters C<a>, C<l>, C<p> and C<h>. |
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444 | These character classes can be part of a larger bracketed character class. For |
445 | example, |
446 | |
447 | [01[:alpha:]%] |
448 | |
449 | is valid and matches '0', '1', any alphabetic character, and the percent sign. |
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450 | |
451 | Perl recognizes the following POSIX character classes: |
452 | |
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453 | alpha Any alphabetical character ("[A-Za-z]"). |
454 | alnum Any alphanumerical character. ("[A-Za-z0-9]") |
455 | ascii Any character in the ASCII character set. |
ea8b8ad2 |
456 | blank A GNU extension, equal to a space or a horizontal tab ("\t"). |
ea449505 |
457 | cntrl Any control character. See Note [2] below. |
458 | digit Any decimal digit ("[0-9]"), equivalent to "\d". |
459 | graph Any printable character, excluding a space. See Note [3] below. |
460 | lower Any lowercase character ("[a-z]"). |
461 | print Any printable character, including a space. See Note [4] below. |
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462 | punct Any graphical character excluding "word" characters. Note [5]. |
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463 | space Any whitespace character. "\s" plus the vertical tab ("\cK"). |
464 | upper Any uppercase character ("[A-Z]"). |
465 | word A Perl extension ("[A-Za-z0-9_]"), equivalent to "\w". |
466 | xdigit Any hexadecimal digit ("[0-9a-fA-F]"). |
467 | |
468 | Most POSIX character classes have two Unicode-style C<\p> property |
469 | counterparts. (They are not official Unicode properties, but Perl extensions |
470 | derived from official Unicode properties.) The table below shows the relation |
471 | between POSIX character classes and these counterparts. |
472 | |
473 | One counterpart, in the column labelled "ASCII-range Unicode" in |
474 | the table will only match characters in the ASCII range. (On EBCDIC platforms, |
475 | they match those characters which have ASCII equivalents.) |
476 | |
477 | The other counterpart, in the column labelled "Full-range Unicode", matches any |
478 | appropriate characters in the full Unicode character set. For example, |
479 | C<\p{Alpha}> will match not just the ASCII alphabetic characters, but any |
480 | character in the entire Unicode character set that is considered to be |
481 | alphabetic. |
482 | |
483 | (Each of the counterparts has various synonyms as well. |
484 | L<perluniprops/Properties accessible through \p{} and \P{}> lists all the |
485 | synonyms, plus all the characters matched by each of the ASCII-range |
486 | properties. For example C<\p{AHex}> is a synonym for C<\p{ASCII_Hex_Digit}>, |
487 | and any C<\p> property name can be prefixed with "Is" such as C<\p{IsAlpha}>.) |
488 | |
489 | Both the C<\p> forms are unaffected by any locale that is in effect, or whether |
490 | the string is in UTF-8 format or not, or whether the platform is EBCDIC or not. |
491 | In contrast, the POSIX character classes are affected. If the source string is |
492 | in UTF-8 format, the POSIX classes (with the exception of C<[[:punct:]]>, see |
493 | Note [5]) behave like their "Full-range" Unicode counterparts. If the source |
494 | string is not in UTF-8 format, and no locale is in effect, and the platform is |
495 | not EBCDIC, all the POSIX classes behave like their ASCII-range counterparts. |
496 | Otherwise, they behave based on the rules of the locale or EBCDIC code page. |
497 | It is proposed to change this behavior in a future release of Perl so that the |
498 | the UTF8ness of the source string will be irrelevant to the behavior of the |
499 | POSIX character classes. This means they will always behave in strict |
500 | accordance with the official POSIX standard. That is, if either locale or |
501 | EBCDIC code page is present, they will behave in accordance with those; if |
502 | absent, the classes will match only their ASCII-range counterparts. If you |
503 | disagree with this proposal, send email to C<perl5-porters@perl.org>. |
504 | |
505 | [[:...:]] ASCII-range Full-range backslash Note |
506 | Unicode Unicode sequence |
507 | ----------------------------------------------------- |
508 | alpha \p{PosixAlpha} \p{Alpha} |
509 | alnum \p{PosixAlnum} \p{Alnum} |
510 | ascii \p{ASCII} |
c1c4ae3a |
511 | blank \p{PosixBlank} \p{Blank} = [1] |
ea449505 |
512 | \p{HorizSpace} \h [1] |
513 | cntrl \p{PosixCntrl} \p{Cntrl} [2] |
514 | digit \p{PosixDigit} \p{Digit} \d |
515 | graph \p{PosixGraph} \p{Graph} [3] |
516 | lower \p{PosixLower} \p{Lower} |
517 | print \p{PosixPrint} \p{Print} [4] |
518 | punct \p{PosixPunct} \p{Punct} [5] |
519 | \p{PerlSpace} \p{SpacePerl} \s [6] |
520 | space \p{PosixSpace} \p{Space} [6] |
521 | upper \p{PosixUpper} \p{Upper} |
522 | word \p{PerlWord} \p{Word} \w |
523 | xdigit \p{ASCII_Hex_Digit} \p{XDigit} |
8a118206 |
524 | |
525 | =over 4 |
526 | |
ea449505 |
527 | =item [1] |
528 | |
529 | C<\p{Blank}> and C<\p{HorizSpace}> are synonyms. |
530 | |
531 | =item [2] |
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532 | |
ea449505 |
533 | Control characters don't produce output as such, but instead usually control |
534 | the terminal somehow: for example newline and backspace are control characters. |
535 | In the ASCII range, characters whose ordinals are between 0 and 31 inclusive, |
536 | plus 127 (C<DEL>) are control characters. |
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537 | |
c1c4ae3a |
538 | On EBCDIC platforms, it is likely that the code page will define C<[[:cntrl:]]> |
539 | to be the EBCDIC equivalents of the ASCII controls, plus the controls |
540 | that in Unicode have ordinals from 128 through 139. |
ea449505 |
541 | |
542 | =item [3] |
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543 | |
544 | Any character that is I<graphical>, that is, visible. This class consists |
545 | of all the alphanumerical characters and all punctuation characters. |
546 | |
ea449505 |
547 | =item [4] |
8a118206 |
548 | |
549 | All printable characters, which is the set of all the graphical characters |
ea449505 |
550 | plus whitespace characters that are not also controls. |
551 | |
552 | =item [5] |
553 | |
554 | C<\p{PosixPunct}> and C<[[:punct:]]> in the ASCII range match all the |
555 | non-controls, non-alphanumeric, non-space characters: |
556 | C<[-!"#$%&'()*+,./:;<=E<gt>?@[\\\]^_`{|}~]> (although if a locale is in effect, |
557 | it could alter the behavior of C<[[:punct:]]>). |
558 | |
559 | When the matching string is in UTF-8 format, C<[[:punct:]]> matches the above |
c1c4ae3a |
560 | set, plus what C<\p{Punct}> matches. This is different than strictly matching |
561 | according to C<\p{Punct}>, because the above set includes characters that aren't |
562 | considered punctuation by Unicode, but rather "symbols". Another way to say it |
563 | is that for a UTF-8 string, C<[[:punct:]]> matches all the characters that |
564 | Unicode considers to be punctuation, plus all the ASCII-range characters that |
565 | Unicode considers to be symbols. |
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566 | |
ea449505 |
567 | =item [6] |
8a118206 |
568 | |
ea449505 |
569 | C<\p{SpacePerl}> and C<\p{Space}> differ only in that C<\p{Space}> additionally |
570 | matches the vertical tab, C<\cK>. Same for the two ASCII-only range forms. |
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571 | |
572 | =back |
573 | |
574 | =head4 Negation |
ea449505 |
575 | X<character class, negation> |
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576 | |
577 | A Perl extension to the POSIX character class is the ability to |
578 | negate it. This is done by prefixing the class name with a caret (C<^>). |
579 | Some examples: |
580 | |
ea449505 |
581 | POSIX ASCII-range Full-range backslash |
582 | Unicode Unicode sequence |
583 | ----------------------------------------------------- |
c1c4ae3a |
584 | [[:^digit:]] \P{PosixDigit} \P{Digit} \D |
ea449505 |
585 | [[:^space:]] \P{PosixSpace} \P{Space} |
c1c4ae3a |
586 | \P{PerlSpace} \P{SpacePerl} \S |
587 | [[:^word:]] \P{PerlWord} \P{Word} \W |
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588 | |
589 | =head4 [= =] and [. .] |
590 | |
591 | Perl will recognize the POSIX character classes C<[=class=]>, and |
ea449505 |
592 | C<[.class.]>, but does not (yet?) support them. Use of |
740bae87 |
593 | such a construct will lead to an error. |
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594 | |
595 | |
596 | =head4 Examples |
597 | |
598 | /[[:digit:]]/ # Matches a character that is a digit. |
599 | /[01[:lower:]]/ # Matches a character that is either a |
600 | # lowercase letter, or '0' or '1'. |
c1c4ae3a |
601 | /[[:digit:][:^xdigit:]]/ # Matches a character that can be anything |
602 | # except the letters 'a' to 'f'. This is |
603 | # because the main character class is composed |
604 | # of two POSIX character classes that are ORed |
605 | # together, one that matches any digit, and |
606 | # the other that matches anything that isn't a |
607 | # hex digit. The result matches all |
608 | # characters except the letters 'a' to 'f' and |
609 | # 'A' to 'F'. |
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610 | |
611 | |
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612 | =head2 Locale, EBCDIC, Unicode and UTF-8 |
8a118206 |
613 | |
614 | Some of the character classes have a somewhat different behaviour depending |
615 | on the internal encoding of the source string, and the locale that is |
ea449505 |
616 | in effect, and if the program is running on an EBCDIC platform. |
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617 | |
618 | C<\w>, C<\d>, C<\s> and the POSIX character classes (and their negations, |
c1c4ae3a |
619 | including C<\W>, C<\D>, C<\S>) suffer from this behaviour. (Since the backslash |
620 | sequences C<\b> and C<\B> are defined in terms of C<\w> and C<\W>, they also are |
621 | affected.) |
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622 | |
623 | The rule is that if the source string is in UTF-8 format, the character |
624 | classes match according to the Unicode properties. If the source string |
ea449505 |
625 | isn't, then the character classes match according to whatever locale or EBCDIC |
626 | code page is in effect. If there is no locale nor EBCDIC, they match the ASCII |
627 | defaults (52 letters, 10 digits and underscore for C<\w>; 0 to 9 for C<\d>; |
c1c4ae3a |
628 | etc.). |
8a118206 |
629 | |
630 | This usually means that if you are matching against characters whose C<ord()> |
631 | values are between 128 and 255 inclusive, your character class may match |
ea449505 |
632 | or not depending on the current locale or EBCDIC code page, and whether the |
633 | source string is in UTF-8 format. The string will be in UTF-8 format if it |
634 | contains characters whose C<ord()> value exceeds 255. But a string may be in |
635 | UTF-8 format without it having such characters. See L<perluniprops/The |
636 | "Unicode Bug">. |
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637 | |
638 | For portability reasons, it may be better to not use C<\w>, C<\d>, C<\s> |
639 | or the POSIX character classes, and use the Unicode properties instead. |
640 | |
641 | =head4 Examples |
642 | |
643 | $str = "\xDF"; # $str is not in UTF-8 format. |
644 | $str =~ /^\w/; # No match, as $str isn't in UTF-8 format. |
645 | $str .= "\x{0e0b}"; # Now $str is in UTF-8 format. |
646 | $str =~ /^\w/; # Match! $str is now in UTF-8 format. |
647 | chop $str; |
648 | $str =~ /^\w/; # Still a match! $str remains in UTF-8 format. |
649 | |
650 | =cut |