Onigmo (Oniguruma-mod) Regular Expressions Version 6.1.0 2016/12/25 syntax: ONIG_SYNTAX_RUBY (default) 1. Syntax elements \ escape (enable or disable meta character) | alternation (...) group [...] character class 2. Characters \t horizontal tab (0x09) \v vertical tab (0x0B) \n newline (line feed) (0x0A) \r carriage return (0x0D) \b backspace (0x08) \f form feed (0x0C) \a bell (0x07) \e escape (0x1B) \nnn octal char (encoded byte value) \xHH hexadecimal char (encoded byte value) \x{7HHHHHHH} wide hexadecimal char (character code point value) \uHHHH wide hexadecimal char (character code point value) \cx control char (character code point value) \C-x control char (character code point value) \M-x meta (x|0x80) (character code point value) \M-\C-x meta control char (character code point value) (* \b as backspace is effective in character class only) * ONIG_SYNTAX_PERL: \o{nnn} (octal char) can be also used. 3. Character types . any character (except newline) \w word character Not Unicode: alphanumeric and "_". Unicode: General_Category -- (Letter|Mark|Number|Connector_Punctuation) It depends on ONIG_OPTION_ASCII_RANGE option that non-ASCII char includes or not. \W non-word char \s whitespace char Not Unicode: \t, \n, \v, \f, \r, \x20 Unicode: 0009, 000A, 000B, 000C, 000D, 0085(NEL), General_Category -- Line_Separator -- Paragraph_Separator -- Space_Separator It depends on ONIG_OPTION_ASCII_RANGE option that non-ASCII char includes or not. \S non-whitespace char \d decimal digit char Unicode: General_Category -- Decimal_Number It depends on ONIG_OPTION_ASCII_RANGE option that non-ASCII char includes or not. \D non-decimal-digit char \h hexadecimal-digit char [0-9a-fA-F] \H non-hexadecimal-digit char Character Property * \p{property-name} * \p{^property-name} (negative) * \P{property-name} (negative) property-name: + works on all encodings Alnum, Alpha, Blank, Cntrl, Digit, Graph, Lower, Print, Punct, Space, Upper, XDigit, Word, ASCII + works on EUC_JP, Shift_JIS, CP932 Hiragana, Katakana, Han, Latin, Greek, Cyrillic + works on UTF-8, UTF-16, UTF-32 see UnicodeProps.txt \p{Punct} works slightly different on Unicode encodings and the other encodings. It matches the nine characters "$+<=>^`|~" on non-Unicode encodings (which is the same as [[:punct:]]), but not on Unicode encodings. \p{XPosixPunct} matches the nine characters on Unicode encodings. \R Linebreak Unicode: (?>\x0D\x0A|[\x0A-\x0D\x{85}\x{2028}\x{2029}]) Not Unicode: (?>\x0D\x0A|[\x0A-\x0D]) \X Extended Grapheme cluster Unicode: See: Unicode Standard Annex #29 UNICODE TEXT SEGMENTATION http://unicode.org/reports/tr29/ Not Unicode: (?>\x0D\x0A|(?m:.)) 4. Quantifier greedy ? 1 or 0 times * 0 or more times + 1 or more times {n,m} at least n but no more than m times {n,} at least n times {,n} at least 0 but no more than n times ({0,n}) {n} n times reluctant ?? 1 or 0 times *? 0 or more times +? 1 or more times {n,m}? at least n but not more than m times {n,}? at least n times {,n}? at least 0 but not more than n times (== {0,n}?) possessive (greedy and does not backtrack once match) ?+ 1 or 0 times *+ 0 or more times ++ 1 or more times ({n,m}+, {n,}+, {n}+ are possessive op. in ONIG_SYNTAX_JAVA and ONIG_SYNTAX_PERL only) ex. /a*+/ === /(?>a*)/ 5. Anchors ^ beginning of the line $ end of the line \b word boundary \B non-word boundary \A beginning of string \Z end of string, or before newline at the end \z end of string \G where the current search attempt begins 6. Character class ^... negative class (lowest precedence) x-y range from x to y [...] set (character class in character class) ..&&.. intersection (low precedence, only higher than ^) ex. [a-w&&[^c-g]z] ==> ([a-w] AND ([^c-g] OR z)) ==> [abh-w] * If you want to use '[', '-', or ']' as a normal character in character class, you should escape them with '\'. POSIX bracket ([:xxxxx:], negate [:^xxxxx:]) Not Unicode Case: alnum alphabet or digit char alpha alphabet ascii code value: [0 - 127] blank \t, \x20 cntrl digit 0-9 graph \x21-\x7E and all of multibyte encoded characters lower print \x20-\x7E and all of multibyte encoded characters punct space \t, \n, \v, \f, \r, \x20 upper xdigit 0-9, a-f, A-F word alphanumeric, "_" and multibyte characters Unicode Case: alnum Letter | Mark | Decimal_Number alpha Letter | Mark ascii 0000 - 007F blank Space_Separator | 0009 cntrl Control | Format | Unassigned | Private_Use | Surrogate digit Decimal_Number graph [[:^space:]] && ^Control && ^Unassigned && ^Surrogate lower Lowercase_Letter print [[:graph:]] | Space_Separator punct Connector_Punctuation | Dash_Punctuation | Close_Punctuation | Final_Punctuation | Initial_Punctuation | Other_Punctuation | Open_Punctuation | 0024 | 002B | 003C | 003D | 003E | 005E | 0060 | 007C | 007E space Space_Separator | Line_Separator | Paragraph_Separator | 0009 | 000A | 000B | 000C | 000D | 0085 upper Uppercase_Letter xdigit 0030 - 0039 | 0041 - 0046 | 0061 - 0066 (0-9, a-f, A-F) word Letter | Mark | Decimal_Number | Connector_Punctuation It depends on ONIG_OPTION_ASCII_RANGE option and ONIG_OPTION_POSIX_BRACKET_ALL_RANGE option that POSIX brackets match non-ASCII char or not. 7. Extended groups (?#...) comment (?imxdau-imx) option on/off i: ignore case m: multi-line (dot (.) also matches newline) x: extended form character set option (character range option) d: Default (compatible with Ruby 1.9.3) \w, \d and \s doesn't match non-ASCII characters. \b, \B and POSIX brackets use the each encoding's rules. a: ASCII ONIG_OPTION_ASCII_RANGE option is turned on. \w, \d, \s and POSIX brackets doesn't match non-ASCII characters. \b and \B use the ASCII rules. u: Unicode ONIG_OPTION_ASCII_RANGE option is turned off. \w (\W), \d (\D), \s (\S), \b (\B) and POSIX brackets use the each encoding's rules. (?imxdau-imx:subexp) option on/off for subexp (?:subexp) non-capturing group (subexp) capturing group (?=subexp) look-ahead (?!subexp) negative look-ahead (?<=subexp) look-behind (?subexp) atomic group no backtracks in subexp. (?subexp), (?'name'subexp) define named group (Each character of the name must be a word character.) Not only a name but a number is assigned like a capturing group. Assigning the same name to two or more subexps is allowed. (?(cond)yes-subexp), (?(cond)yes-subexp|no-subexp) conditional expression Matches yes-subexp if (cond) yields a true value, matches no-subexp otherwise. Following (cond) can be used: (n) (n >= 1) Checks if the numbered capturing group has matched something. (), ('name') Checks if a group with the given name has matched something. BUG: If the name is defined more than once, the left-most group is checked, but it should be the same as \k. (?~subexp) absence operator (experimental) Matches any string which doesn't contain any string which matches subexp. More precisely, (?~subexp) matches the complement set of a set which .*subexp.* matches. This is regular in the meaning of formal language theory. Similar to (?:(?!subexp).)*, but easy to write. E.g.: (?~abc) matches: "", "ab", "aab", "ccdd", etc. It doesn't match: "abc", "aabc", "ccabcdd", etc. \/\*(?~\*\/)\*\/ matches C style comments: "/**/", "/* foobar */", etc. \A\/\*(?~\*\/)\*\/\z doesn't match "/**/ */". This is different from \A\/\*.*?\*\/\z which uses a reluctant quantifier (.*?). Unlike (?:(?!abc).)*c, (?~abc)c matches "abc", because (?~abc) matches "ab". (?~) never matches. Theoretical backgrounds are discussed in Tanaka Akira's paper and slide (both Japanese): * Absent Operator for Regular Expression https://staff.aist.go.jp/tanaka-akira/pub/prosym49-akr-paper.pdf * 正規表現における非包含オペレータの提案 https://staff.aist.go.jp/tanaka-akira/pub/prosym49-akr-presen.pdf 8. Backreferences When we say "backreference a group," it actually means, "re-match the same text matched by the subexp in that group." \n \k \k'n' (n >= 1) backreference the nth group in the regexp \k<-n> \k'-n' (n >= 1) backreference the nth group counting backwards from the referring position \k \k'name' backreference a group with the specified name When backreferencing with a name that is assigned to more than one groups, the last group with the name is checked first, if not matched then the previous one with the name, and so on, until there is a match. * Backreference by number is forbidden if any named group is defined and ONIG_OPTION_CAPTURE_GROUP is not set. * ONIG_SYNTAX_PERL: \g{n}, \g{-n} and \g{name} can also be used. If a name is defined more than once in Perl syntax, only the left-most group is checked. backreference with recursion level (n >= 1, level >= 0) \k \k'n+level' \k \k'n-level' \k<-n+level> \k'-n+level' \k<-n-level> \k'-n-level' \k \k'name+level' \k \k'name-level' Destine a group on the recursion level relative to the referring position. ex 1. /\A(?|.|(?:(?.)\g\k))\z/.match("reee") /\A(?|.|(?:(?.)\g\k))\z/.match("reer") \k refers to the (?.) on the same recursion level with it. ex 2. r = Regexp.compile(<<'__REGEXP__'.strip, Regexp::EXTENDED) (? \g \g* \g ){0} (? < \g \s* > ){0} (? [a-zA-Z_:]+ ){0} (? [^<&]+ (\g | [^<&]+)* ){0} (? >){0} \g __REGEXP__ p r.match("fbbbf").captures 9. Subexp calls ("Tanaka Akira special") When we say "call a group," it actually means, "re-execute the subexp in that group." \g<0> \g'0' call the whole pattern recursively \g \g'n' (n >= 1) call the nth group \g<-n> \g'-n' (n >= 1) call the nth group counting backwards from the calling position \g<+n> \g'+n' (n >= 1) call the nth group counting forwards from the calling position \g \g'name' call the group with the specified name * Left-most recursive calls are not allowed. ex. (?a|\gb) => error (?a|b\gc) => OK * Calls with a name that is assigned to more than one groups are not allowed in ONIG_SYNTAX_RUBY. * Call by number is forbidden if any named group is defined and ONIG_OPTION_CAPTURE_GROUP is not set. * The option status of the called group is always effective. ex. /(?-i:\g)(?i:(?a)){0}/.match("A") * ONIG_SYNTAX_PERL: Use (?&name), (?n), (?-n), (?+n), (?R) or (?0) instead of \g<>. Calls with a name that is assigned to more than one groups are allowed, and the left-most subexp is used. 10. Captured group Behavior of an unnamed group (...) changes with the following conditions. (But named group is not changed.) case 1. /.../ (named group is not used, no option) (...) is treated as a capturing group. case 2. /.../g (named group is not used, 'g' option) (...) is treated as a non-capturing group (?:...). case 3. /..(?..)../ (named group is used, no option) (...) is treated as a non-capturing group. numbered-backref/call is not allowed. case 4. /..(?..)../G (named group is used, 'G' option) (...) is treated as a capturing group. numbered-backref/call is allowed. where g: ONIG_OPTION_DONT_CAPTURE_GROUP G: ONIG_OPTION_CAPTURE_GROUP ('g' and 'G' options are argued in ruby-dev ML) ----------------------------- A-1. Syntax-dependent options + ONIG_SYNTAX_RUBY (?m): dot (.) also matches newline + ONIG_SYNTAX_PERL, ONIG_SYNTAX_JAVA and ONIG_SYNTAX_PYTHON (?s): dot (.) also matches newline (?m): ^ matches after newline, $ matches before newline + ONIG_SYNTAX_PERL (?d), (?l): same as (?u) A-2. Original extensions + hexadecimal digit char type \h, \H + named group (?...), (?'name'...) + named backref \k + subexp call \g, \g A-3. Missing features compared with perl 5.18.0 + \N{name}, \N{U+xxxx}, \N + \l,\u,\L,\U, \C + \v, \V, \h, \H + (?{code}) + (??{code}) + (?|...) + (?[]) + (*VERB:ARG) * \Q...\E This is effective on ONIG_SYNTAX_PERL and ONIG_SYNTAX_JAVA. A-4. Differences with Japanized GNU regex(version 0.12) of Ruby 1.8 + add character property (\p{property}, \P{property}) + add hexadecimal digit char type (\h, \H) + add look-behind (?<=fixed-width-pattern), (?>]/ in EUC-JP encoding. + effect range of isolated option is to next ')'. ex. (?:(?i)a|b) is interpreted as (?:(?i:a|b)), not (?:(?i:a)|b). + isolated option is not transparent to previous pattern. ex. a(?i)* is a syntax error pattern. + allowed unpaired left brace as a normal character. ex. /{/, /({)/, /a{2,3/ etc... + negative POSIX bracket [:^xxxx:] is supported. + POSIX bracket [:ascii:] is added. + repeat of look-ahead is not allowed. ex. /(?=a)*/, /(?!b){5}/ + Ignore case option is effective to escape sequence. ex. /\x61/i =~ "A" + In the range quantifier, the number of the minimum is optional. /a{,n}/ == /a{0,n}/ The omission of both minimum and maximum values is not allowed. /a{,}/ + /{n}?/ is not a reluctant quantifier. /a{n}?/ == /(?:a{n})?/ + invalid back reference is checked and raises error. /\1/, /(a)\2/ + Zero-width match in an infinite loop stops the repeat, then changes of the capture group status are checked as stop condition. /(?:()|())*\1\2/ =~ "" /(?:\1a|())*/ =~ "a" A-5. Features disabled in default syntax + capture history (?@...) and (?@...) ex. /(?@a)*/.match("aaa") ==> [<0-1>, <1-2>, <2-3>] see sample/listcap.c file. A-6. Problems + Invalid encoding byte sequence is not checked. ex. UTF-8 * Invalid first byte is treated as a character. /./u =~ "\xa3" * Incomplete byte sequence is not checked. /\w+/ =~ "a\xf3\x8ec" // END