| This page lists the regular expression syntax accepted by RE2. |
| It also lists syntax accepted by PCRE, PERL, and VIM. |
Grayed out expressions are not supported by RE2.
|
|
| Single characters: |
| . | any character, including newline (s=true) |
| [xyz] | character class |
| [^xyz] | negated character class |
| \d | Perl character class |
| \D | negated Perl character class |
| [:alpha:] | ASCII character class |
| [:^alpha:] | negated ASCII character class |
| \pN | Unicode character class (one-letter name) |
| \p{Greek} | Unicode character class |
| \PN | negated Unicode character class (one-letter name) |
| \P{Greek} | negated Unicode character class |
|
| Composites: |
| xy | x followed by y |
| x|y | x or y (prefer x) |
|
| Repetitions: |
| x* | zero or more x, prefer more |
| x+ | one or more x, prefer more |
| x? | zero or one x, prefer one |
| x{n,m} | n or n+1 or ... or m x, prefer more |
| x{n,} | n or more x, prefer more |
| x{n} | exactly n x |
| x*? | zero or more x, prefer fewer |
| x+? | one or more x, prefer fewer |
| x?? | zero or one x, prefer zero |
| x{n,m}? | n or n+1 or ... or m x, prefer fewer |
| x{n,}? | n or more x, prefer fewer |
| x{n}? | exactly n x |
| x{} | (≡ x*) (NOT SUPPORTED) VIM |
| x{-} | (≡ x*?) (NOT SUPPORTED) VIM |
| x{-n} | (≡ x{n}?) (NOT SUPPORTED) VIM |
| x= | (≡ x?) (NOT SUPPORTED) VIM
|
|
Possessive repetitions: |
| x*+ | zero or more x, possessive (NOT SUPPORTED) |
| x++ | one or more x, possessive (NOT SUPPORTED) |
| x?+ | zero or one x, possessive (NOT SUPPORTED) |
| x{n,m}+ | n or ... or m x, possessive (NOT SUPPORTED) |
| x{n,}+ | n or more x, possessive (NOT SUPPORTED) |
| x{n}+ | exactly n x, possessive (NOT SUPPORTED) |
|
| Grouping: |
| (re) | numbered capturing group |
| (?P<name>re) | named & numbered capturing group |
| (?<name>re) | named & numbered capturing group (NOT SUPPORTED) |
| (?'name're) | named & numbered capturing group (NOT SUPPORTED) |
| (?:re) | non-capturing group |
| (?flags) | set flags until outer paren closes; non-capturing |
| (?flags:re) | set flags during re; non-capturing |
| (?#text) | comment (NOT SUPPORTED) |
| (?|x|y|z) | branch numbering reset (NOT SUPPORTED) |
| (?>re) | possessive match of re (NOT SUPPORTED) |
| re@> | possessive match of re (NOT SUPPORTED) VIM |
| %(re) | non-capturing group (NOT SUPPORTED) VIM |
|
| Flags: |
| i | case-insensitive (default false) |
| m | multi-line mode (default false) |
| s | let . match \n (default false) |
| U | ungreedy: swap meaning of x* and x*?, x+ and x+?, etc (default false) |
| Flag syntax is xyz (set) or -xyz (clear) or xy-z (set xy, clear z). |
|
| Empty strings: |
| ^ | at beginning of text or line (m=true) |
| $ | at end of text (like \z not \Z) or line (m=true) |
| \A | at beginning of text |
| \b | at word boundary (\w on one side and \W, \A, or \z on the other) |
| \B | not a word boundary |
| \G | at beginning of subtext being searched (NOT SUPPORTED) PCRE |
| \G | at end of last match (NOT SUPPORTED) PERL |
| \Z | at end of text, or before newline at end of text (NOT SUPPORTED) |
| \z | at end of text |
| (?=re) | before text matching re (NOT SUPPORTED) |
| (?!re) | before text not matching re (NOT SUPPORTED) |
| (?<=re) | after text matching re (NOT SUPPORTED) |
| (?<!re) | after text not matching re (NOT SUPPORTED) |
| re& | before text matching re (NOT SUPPORTED) VIM |
| re@= | before text matching re (NOT SUPPORTED) VIM |
| re@! | before text not matching re (NOT SUPPORTED) VIM |
| re@<= | after text matching re (NOT SUPPORTED) VIM |
| re@<! | after text not matching re (NOT SUPPORTED) VIM |
| \zs | sets start of match (= \K) (NOT SUPPORTED) VIM |
| \ze | sets end of match (NOT SUPPORTED) VIM |
| \%^ | beginning of file (NOT SUPPORTED) VIM |
| \%$ | end of file (NOT SUPPORTED) VIM |
| \%V | on screen (NOT SUPPORTED) VIM |
| \%# | cursor position (NOT SUPPORTED) VIM |
| \%'m | mark m position (NOT SUPPORTED) VIM |
| \%23l | in line 23 (NOT SUPPORTED) VIM |
| \%23c | in column 23 (NOT SUPPORTED) VIM |
| \%23v | in virtual column 23 (NOT SUPPORTED) VIM |
|
| Escape sequences: |
| \a | bell (≡ \007) |
| \f | form feed (≡ \014) |
| \t | horizontal tab (≡ \011) |
| \n | newline (≡ \012) |
| \r | carriage return (≡ \015) |
| \v | vertical tab character (≡ \013) |
| \* | literal *, for any punctuation character * |
| \123 | octal character code (up to three digits) |
| \x7F | hex character code (exactly two digits) |
| \x{10FFFF} | hex character code |
| \C | match a single byte even in UTF-8 mode |
| \Q...\E | literal text ... even if ... has punctuation |
|
| \1 | backreference (NOT SUPPORTED) |
| \b | backspace (NOT SUPPORTED) (use \010) |
| \cK | control char ^K (NOT SUPPORTED) (use \001 etc) |
| \e | escape (NOT SUPPORTED) (use \033) |
| \g1 | backreference (NOT SUPPORTED) |
| \g{1} | backreference (NOT SUPPORTED) |
| \g{+1} | backreference (NOT SUPPORTED) |
| \g{-1} | backreference (NOT SUPPORTED) |
| \g{name} | named backreference (NOT SUPPORTED) |
| \g<name> | subroutine call (NOT SUPPORTED) |
| \g'name' | subroutine call (NOT SUPPORTED) |
| \k<name> | named backreference (NOT SUPPORTED) |
| \k'name' | named backreference (NOT SUPPORTED) |
| \lX | lowercase X (NOT SUPPORTED) |
| \ux | uppercase x (NOT SUPPORTED) |
| \L...\E | lowercase text ... (NOT SUPPORTED) |
| \K | reset beginning of $0 (NOT SUPPORTED) |
| \N{name} | named Unicode character (NOT SUPPORTED) |
| \R | line break (NOT SUPPORTED) |
| \U...\E | upper case text ... (NOT SUPPORTED) |
| \X | extended Unicode sequence (NOT SUPPORTED) |
|
| \%d123 | decimal character 123 (NOT SUPPORTED) VIM |
| \%xFF | hex character FF (NOT SUPPORTED) VIM |
| \%o123 | octal character 123 (NOT SUPPORTED) VIM |
| \%u1234 | Unicode character 0x1234 (NOT SUPPORTED) VIM |
| \%U12345678 | Unicode character 0x12345678 (NOT SUPPORTED) VIM |
|
| Character class elements: |
| x | single character |
| A-Z | character range (inclusive) |
| \d | Perl character class |
| [:foo:] | ASCII character class foo |
| \p{Foo} | Unicode character class Foo |
| \pF | Unicode character class F (one-letter name) |
|
| Named character classes as character class elements: |
| [\d] | digits (≡ \d) |
| [^\d] | not digits (≡ \D) |
| [\D] | not digits (≡ \D) |
| [^\D] | not not digits (≡ \d) |
| [[:name:]] | named ASCII class inside character class (≡ [:name:]) |
| [^[:name:]] | named ASCII class inside negated character class (≡ [:^name:]) |
| [\p{Name}] | named Unicode property inside character class (≡ \p{Name}) |
| [^\p{Name}] | named Unicode property inside negated character class (≡ \P{Name}) |
|
| Perl character classes: |
| \d | digits (≡ [0-9]) |
| \D | not digits (≡ [^0-9]) |
| \s | whitespace (≡ [\t\n\f\r ]) |
| \S | not whitespace (≡ [^\t\n\f\r ]) |
| \w | word characters (≡ [0-9A-Za-z_]) |
| \W | not word characters (≡ [^0-9A-Za-z_]) |
|
| \h | horizontal space (NOT SUPPORTED) |
| \H | not horizontal space (NOT SUPPORTED) |
| \v | vertical space (NOT SUPPORTED) |
| \V | not vertical space (NOT SUPPORTED) |
|
| ASCII character classes: |
| [:alnum:] | alphanumeric (≡ [0-9A-Za-z]) |
| [:alpha:] | alphabetic (≡ [A-Za-z]) |
| [:ascii:] | ASCII (≡ [\x00-\x7F]) |
| [:blank:] | blank (≡ [\t ]) |
| [:cntrl:] | control (≡ [\x00-\x1F\x7F]) |
| [:digit:] | digits (≡ [0-9]) |
| [:graph:] | graphical (≡ [!-~] == [A-Za-z0-9!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~]) |
| [:lower:] | lower case (≡ [a-z]) |
| [:print:] | printable (≡ [ -~] == [ [:graph:]]) |
| [:punct:] | punctuation (≡ [!-/:-@[-`{-~]) |
| [:space:] | whitespace (≡ [\t\n\v\f\r ]) |
| [:upper:] | upper case (≡ [A-Z]) |
| [:word:] | word characters (≡ [0-9A-Za-z_]) |
| [:xdigit:] | hex digit (≡ [0-9A-Fa-f]) |
|
| Unicode character class names--general category: |
| C | other |
| Cc | control |
| Cf | format |
| Cn | unassigned code points (NOT SUPPORTED) |
| Co | private use |
| Cs | surrogate |
| L | letter |
| LC | cased letter (NOT SUPPORTED) |
| L& | cased letter (NOT SUPPORTED) |
| Ll | lowercase letter |
| Lm | modifier letter |
| Lo | other letter |
| Lt | titlecase letter |
| Lu | uppercase letter |
| M | mark |
| Mc | spacing mark |
| Me | enclosing mark |
| Mn | non-spacing mark |
| N | number |
| Nd | decimal number |
| Nl | letter number |
| No | other number |
| P | punctuation |
| Pc | connector punctuation |
| Pd | dash punctuation |
| Pe | close punctuation |
| Pf | final punctuation |
| Pi | initial punctuation |
| Po | other punctuation |
| Ps | open punctuation |
| S | symbol |
| Sc | currency symbol |
| Sk | modifier symbol |
| Sm | math symbol |
| So | other symbol |
| Z | separator |
| Zl | line separator |
| Zp | paragraph separator |
| Zs | space separator |
|
| Unicode character class names--scripts: |
| Arabic | Arabic |
| Armenian | Armenian |
| Balinese | Balinese |
| Bengali | Bengali |
| Bopomofo | Bopomofo |
| Braille | Braille |
| Buginese | Buginese |
| Buhid | Buhid |
| Canadian_Aboriginal | Canadian Aboriginal |
| Carian | Carian |
| Cham | Cham |
| Cherokee | Cherokee |
| Common | characters not specific to one script |
| Coptic | Coptic |
| Cuneiform | Cuneiform |
| Cypriot | Cypriot |
| Cyrillic | Cyrillic |
| Deseret | Deseret |
| Devanagari | Devanagari |
| Ethiopic | Ethiopic |
| Georgian | Georgian |
| Glagolitic | Glagolitic |
| Gothic | Gothic |
| Greek | Greek |
| Gujarati | Gujarati |
| Gurmukhi | Gurmukhi |
| Han | Han |
| Hangul | Hangul |
| Hanunoo | Hanunoo |
| Hebrew | Hebrew |
| Hiragana | Hiragana |
| Inherited | inherit script from previous character |
| Kannada | Kannada |
| Katakana | Katakana |
| Kayah_Li | Kayah Li |
| Kharoshthi | Kharoshthi |
| Khmer | Khmer |
| Lao | Lao |
| Latin | Latin |
| Lepcha | Lepcha |
| Limbu | Limbu |
| Linear_B | Linear B |
| Lycian | Lycian |
| Lydian | Lydian |
| Malayalam | Malayalam |
| Mongolian | Mongolian |
| Myanmar | Myanmar |
| New_Tai_Lue | New Tai Lue (aka Simplified Tai Lue) |
| Nko | Nko |
| Ogham | Ogham |
| Ol_Chiki | Ol Chiki |
| Old_Italic | Old Italic |
| Old_Persian | Old Persian |
| Oriya | Oriya |
| Osmanya | Osmanya |
| Phags_Pa | 'Phags Pa |
| Phoenician | Phoenician |
| Rejang | Rejang |
| Runic | Runic |
| Saurashtra | Saurashtra |
| Shavian | Shavian |
| Sinhala | Sinhala |
| Sundanese | Sundanese |
| Syloti_Nagri | Syloti Nagri |
| Syriac | Syriac |
| Tagalog | Tagalog |
| Tagbanwa | Tagbanwa |
| Tai_Le | Tai Le |
| Tamil | Tamil |
| Telugu | Telugu |
| Thaana | Thaana |
| Thai | Thai |
| Tibetan | Tibetan |
| Tifinagh | Tifinagh |
| Ugaritic | Ugaritic |
| Vai | Vai |
| Yi | Yi |
|
| Vim character classes: |
| \i | identifier character (NOT SUPPORTED) VIM |
| \I | \i except digits (NOT SUPPORTED) VIM |
| \k | keyword character (NOT SUPPORTED) VIM |
| \K | \k except digits (NOT SUPPORTED) VIM |
| \f | file name character (NOT SUPPORTED) VIM |
| \F | \f except digits (NOT SUPPORTED) VIM |
| \p | printable character (NOT SUPPORTED) VIM |
| \P | \p except digits (NOT SUPPORTED) VIM |
| \s | whitespace character (≡ [ \t]) (NOT SUPPORTED) VIM |
| \S | non-white space character (≡ [^ \t]) (NOT SUPPORTED) VIM |
| \d | digits (≡ [0-9]) VIM |
| \D | not \d VIM |
| \x | hex digits (≡ [0-9A-Fa-f]) (NOT SUPPORTED) VIM |
| \X | not \x (NOT SUPPORTED) VIM |
| \o | octal digits (≡ [0-7]) (NOT SUPPORTED) VIM |
| \O | not \o (NOT SUPPORTED) VIM |
| \w | word character VIM |
| \W | not \w VIM |
| \h | head of word character (NOT SUPPORTED) VIM |
| \H | not \h (NOT SUPPORTED) VIM |
| \a | alphabetic (NOT SUPPORTED) VIM |
| \A | not \a (NOT SUPPORTED) VIM |
| \l | lowercase (NOT SUPPORTED) VIM |
| \L | not lowercase (NOT SUPPORTED) VIM |
| \u | uppercase (NOT SUPPORTED) VIM |
| \U | not uppercase (NOT SUPPORTED) VIM |
| \_x | \x plus newline, for any x (NOT SUPPORTED) VIM |
|
| Vim flags: |
| \c | ignore case (NOT SUPPORTED) VIM |
| \C | match case (NOT SUPPORTED) VIM |
| \m | magic (NOT SUPPORTED) VIM |
| \M | nomagic (NOT SUPPORTED) VIM |
| \v | verymagic (NOT SUPPORTED) VIM |
| \V | verynomagic (NOT SUPPORTED) VIM |
| \Z | ignore differences in Unicode combining characters (NOT SUPPORTED) VIM |
|
| Magic: |
| (?{code}) | arbitrary Perl code (NOT SUPPORTED) PERL |
| (??{code}) | postponed arbitrary Perl code (NOT SUPPORTED) PERL |
| (?n) | recursive call to regexp capturing group n (NOT SUPPORTED) |
| (?+n) | recursive call to relative group +n (NOT SUPPORTED) |
| (?-n) | recursive call to relative group -n (NOT SUPPORTED) |
| (?C) | PCRE callout (NOT SUPPORTED) PCRE |
| (?R) | recursive call to entire regexp (≡ (?0)) (NOT SUPPORTED) |
| (?&name) | recursive call to named group (NOT SUPPORTED) |
| (?P=name) | named backreference (NOT SUPPORTED) |
| (?P>name) | recursive call to named group (NOT SUPPORTED) |
| (?(cond)true|false) | conditional branch (NOT SUPPORTED) |
| (?(cond)true) | conditional branch (NOT SUPPORTED) |
| (*ACCEPT) | make regexps more like Prolog (NOT SUPPORTED) |
| (*COMMIT) | (NOT SUPPORTED) |
| (*F) | (NOT SUPPORTED) |
| (*FAIL) | (NOT SUPPORTED) |
| (*MARK) | (NOT SUPPORTED) |
| (*PRUNE) | (NOT SUPPORTED) |
| (*SKIP) | (NOT SUPPORTED) |
| (*THEN) | (NOT SUPPORTED) |
| (*ANY) | set newline convention (NOT SUPPORTED) |
| (*ANYCRLF) | (NOT SUPPORTED) |
| (*CR) | (NOT SUPPORTED) |
| (*CRLF) | (NOT SUPPORTED) |
| (*LF) | (NOT SUPPORTED) |
| (*BSR_ANYCRLF) | set \R convention (NOT SUPPORTED) PCRE |
| (*BSR_UNICODE) | (NOT SUPPORTED) PCRE |
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