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| Construct | Matches |
|---|---|
| Characters | |
| x | The character x |
| \\\\ | The backslash character |
| \\0n | The character with octal value 0n (0 <= n <= 7) |
| \\0nn | The character with octal value 0nn (0 <= n <= 7) |
| \\0mnn | The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7) |
| \\xhh | The character with hexadecimal value 0xhh |
| \uhhhh | The character with hexadecimal value 0xhhhh |
| \\t | The tab character ('\u0009') |
| \\n | The newline (line feed) character ('\u000A') |
| \\r | The carriage-return character ('\u000D') |
| \\f | The form-feed character ('\u000C') |
| \\a | The alert (bell) character ('\u0007') |
| \\e | The escape character ('\u001B') |
| \\cx | The control character corresponding to x |
| Character classes | |
| [abc] | a, b, or c (simple class) |
| [^abc] | Any character except a, b, or c (negation) |
| [a-zA-Z] | a through z or A through Z, inclusive (range) |
| [a-d[m-p]] | a through d, or m through p: [a-dm-p] (union) |
| [a-z&&[def]] | d, e, or f (intersection) |
| [a-z&&[^bc]] | a through z, except for b and c: [ad-z] (subtraction) |
| [a-z&&[^m-p]] | a through z, and not m through p: [a-lq-z](subtraction) |
| Predefined character classes | |
| . | Any character (may or may not match line terminators) |
| \\d | A digit: [0-9] |
| \\D | A non-digit: [^0-9] |
| \\s | A whitespace character: [ \\t\\n\\x0B\\f\\r] |
| \\S | A non-whitespace character: [^\\s] |
| \\w | A word character: [a-zA-Z_0-9] |
| \\W | A non-word character: [^\\w] |
| POSIX character classes (US-ASCII only) | |
| \\p{Lower} | A lower-case alphabetic character: [a-z] |
| \\p{Upper} | An upper-case alphabetic character:[A-Z] |
| \\p{ASCII} | All ASCII:[\\x00-\\x7F] |
| \\p{Alpha} | An alphabetic character:[\\p{Lower}\\p{Upper}] |
| \\p{Digit} | A decimal digit: [0-9] |
| \\p{Alnum} | An alphanumeric character:[\\p{Alpha}\\p{Digit}] |
| \\p{Punct} | Punctuation: One of !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ |
| \\p{Graph} | A visible character: [\\p{Alnum}\\p{Punct}] |
| \\p{Print} | A printable character: [\\p{Graph}] |
| \\p{Blank} | A space or a tab: [ \\t] |
| \\p{Cntrl} | A control character: [\\x00-\\x1F\\x7F] |
| \\p{XDigit} | A hexadecimal digit: [0-9a-fA-F] |
| \\p{Space} | A whitespace character: [ \\t\\n\\x0B\\f\\r] |
| Classes for Unicode blocks and categories | |
| \\p{InGreek} | A character in the Greek block (simple href="#ubc">blockblock) |
| \\p{Lu} | An uppercase letter (simple href="#ubc">categorycategory) |
| \\p{Sc} | A currency symbol |
| \\P{InGreek} | Any character except one in the Greek block (negation) |
| [\\p{L}&&[^\\p{Lu}]] | Any letter except an uppercase letter (subtraction) |
| Boundary matchers | |
| ^ | The beginning of a line |
| $ | The end of a line |
| \\b | A word boundary |
| \\B | A non-word boundary |
| \\A | The beginning of the input |
| \\G | The end of the previous match |
| \\Z | The end of the input but for the final href="#lt">terminator terminator, if any |
| \\z | The end of the input |
| Greedy quantifiers | |
| X? | X, once or not at all |
| X* | X, zero or more times |
| X+ | X, one or more times |
| X{n} | X, exactly n times |
| X{n,} | X, at least n times |
| X{n,m} | X, at least n but not more than m times |
| Reluctant quantifiers | |
| X?? | X, once or not at all |
| X*? | X, zero or more times |
| X+? | X, one or more times |
| X{n}? | X, exactly n times |
| X{n,}? | X, at least n times |
| X{n,m}? | X, at least n but not more than m times |
| Possessive quantifiers | |
| X?+ | X, once or not at all |
| X*+ | X, zero or more times |
| X++ | X, one or more times |
| X{n}+ | X, exactly n times |
| X{n,}+ | X, at least n times |
| X{n,m}+ | X, at least n but not more than m times |
| Logical operators | |
| XY | X followed by Y |
| X|Y | Either X or Y |
| (X) | X, as a href="#cg">capturing capturing group |
| Back references | |
| $n | Whatever the nth href="#cg">capturing capturing group matched |
| Quotation | |
| \\ | Nothing, but quotes the following character |
| \\Q | Nothing, but quotes all characters until \\E |
| \\E | Nothing, but ends quoting started by \\Q |
| Special constructs (non-capturing) | |
| (?:X) | X, as a non-capturing group |
| (?idmsux-idmsux) | Nothing, but turns match flags on - off |
| (?idmsux-idmsux:X) | X, as a href="#cg">nona non-capturing group with the given flags on - off |
| (?=X) | X, via zero-width positive lookahead |
| (?!X) | X, via zero-width negative lookahead |
| (?<=X) | X, via zero-width positive lookbehind |
| (?<!X) | X, via zero-width negative lookbehind |
| (?>X) | X, as an independent, non-capturing group |
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