Oniguruma Regular Expressions Version 6.8.0 2018/04/13
syntax: ONIG_SYNTAX_ONIGURUMA (default)
1. Syntax elements(语法元素)
\ 转译
| 或
(...) 分组
[...] character class
2. Characters(字符)
\t horizontal tab(制表符) (0x09)
\v vertical tab(垂直制表符) (0x0B)
\n newline (换行) (0x0A)
\r carriage return(回车) (0x0D)
\b backspace(匹配任何空白符，等价于[\f\n\r\t\v]) (0x08)
(* \b as backspace is effective in character class only)
\f form feed(换页) (0x0C)
\a bell (0x07)
\e escape (0x1B)
\nnn octal char (encoded byte value)
\o{17777777777} wide octal char (character code point value)
\uHHHH wide hexadecimal char (character code point value)
\xHH hexadecimal char (encoded byte value)
\x{7HHHHHHH} 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)
3. Character types(字符类型)
. any character (except newline)（除换行符之外的任何单字符）
\w word character（单词，等价于[A-Za-z0-9_]）
\W non-word char（等价于[^A-Za-z0-9_]）
\s whitespace char(匹配任何白字符。等价于[^\f\n\r\t\v])
\S 匹配非空白字符
\d 匹配数字字符
\D 匹配非数字字符
\h 匹配十六进制字符 [0-9a-fA-F]
\H 匹配非十六进制字符
\R 通用换行符 (* 不能用于字符类)
"\r\n" or \n,\v,\f,\r (* but doesn't backtrack from \r\n to \r)
\N negative newline (?-m:.)
\O true anychar (?m:.) (* original function)
\X Extended Grapheme Cluster (?>\O(?:\Y\O)*)
Character Property(字符属性)
* \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
Hiragana, Katakana
+ works on UTF8, UTF16, UTF32
See doc/UNICODE_PROPERTIES.
4. Quantifier(量词)
greedy(贪婪的)
? 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(不情愿的，勉强的)
?? 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(占有的) (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 only)
ex. /a*+/ === /(?>a*)/
5. Anchors(锚,固定)
^ beginning of the line
$ end of the line
\b word boundary
\B non-word boundary
\y Extended Grapheme Cluster boundary
\Y Extended Grapheme Cluster non-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
\K keep (keep start position of the result string)
6. Character class（字符类）
^... 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 include all of multibyte encoded characters
lower
print include 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:]]
punct Connector_Punctuation | Dash_Punctuation | Close_Punctuation |
Final_Punctuation | Initial_Punctuation | Other_Punctuation |
Open_Punctuation
space Space_Separator | Line_Separator | Paragraph_Separator |
U+0009 | U+000A | U+000B | U+000C | U+000D | U+0085
upper Uppercase_Letter
xdigit U+0030 - U+0039 | U+0041 - U+0046 | U+0061 - U+0066
(0-9, a-f, A-F)
word Letter | Mark | Decimal_Number | Connector_Punctuation
7. Extended groups
(?#...) comment
(?imxWDSP-imxWDSP) option on/off
i: ignore case
m: multi-line (dot (.) also matches newline)
x: extended form
W: ASCII only word (\w, \p{Word}, [[:word:]])
ASCII only word bound (\b)
D: ASCII only digit (\d, \p{Digit}, [[:digit:]])
S: ASCII only space (\s, \p{Space}, [[:space:]])
P: ASCII only POSIX properties (includes W,D,S)
(alnum, alpha, blank, cntrl, digit, graph,
lower, print, punct, space, upper, xdigit, word)
(?imxWDSP-imxWDSP:subexp) option on/off for subexp
(?:subexp) non-capturing group(非俘获组)
(subexp) capturing group(俘获组)
(?=subexp) look-ahead(前缀符合表达式subexp的集合中查找字符串，即在任何匹配字符串subexp的字符串开始处匹配查找字符串)
(?!subexp) negative look-ahead(在任何不匹配subexp的字符串开始处匹配查找字符串)
(?<=subexp) look-behind
(?<!subexp) negative look-behind
(?>subexp) atomic group
no backtracks in subexp.(子表达式中子没有回溯)
(?<name>subexp), (?'name'subexp)
define named group
定义命名组
(Each character of the name must be a word character.)
名称的每个字符必须是一个单词字符
Not only a name but a number is assigned like a capturing
group.
Assigning the same name to two or more subexps is allowed.
允许将相同的名称分配给两个或多个子表达式
<Callouts>
* Callouts of contents
(?{...contents...}) callout in progress
(?{...contents...}D) D is a direction flag char
D = 'X': in progress and retraction
'<': in retraction only
'>': in progress only
(?{...contents...}[tag]) tag assigned
(?{...contents...}[tag]D)
* Escape characters have no effects in contents.
* contents is not allowed to start with '{'.
(?{{{...contents...}}}) n times continuations '}' in contents is allowed in
(n+1) times continuations {{{...}}}.
Allowed tag string characters: _ A-Z a-z 0-9 (* first character: _ A-Z a-z)
* Callouts of name
(*name)
(*name{args...}) with args
(*name[tag]) tag assigned
(*name[tag]{args...})
Allowed name string characters: _ A-Z a-z 0-9 (* first character: _ A-Z a-z)
Allowed tag string characters: _ A-Z a-z 0-9 (* first character: _ A-Z a-z)
<Absent functions>
(?~absent) Absent repeater (* proposed by Tanaka Akira)
This works like .* (more precisely \O*), but it is
limited by the range that does not include the string
match with <absent>.
This is a written abbreviation of (?~|absent|\O*).
\O* is used as a repeater.
(?~|absent|exp) Absent expression (* original)
This works like "exp", but it is limited by the range
that does not include the string match with <absent>.
ex. (?~|345|\d*) "12345678" ==> "12", "1", ""
(?~|absent) Absent stopper (* original)
After passed this operator, string right range is limited
at the point that does not include the string match whth
<absent>.
(?~|) Range clear
Clear the effects caused by Absent stoppers.
* Nested Absent functions are not supported and the behavior
is undefined.
<if-then-else>
(?(condition_exp)then_exp|else_exp) if-then-else
(?(condition_exp)then_exp) if-then
condition_exp can be a backreference number/name or a normal
regular expression.
When condition_exp is a backreference number/name, both then_exp and
else_exp can be omitted.
Then it works as a backreference validity checker.
[ backreference validity checker ] (* original)
(?(n)), (?(-n)), (?(+n)), (?(n+level)) ...
(?(<n>)), (?('-n')), (?(<+n>)) ...
(?(<name>)), (?('name')), (?(<name+level>)) ...
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<n> \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<+n> \k'+n' (n >= 1) backreference the nth group counting
forwards from the referring position
\k<name> \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.
backreference with recursion level
(n >= 1, level >= 0)
\k<n+level> \k'n+level'
\k<n-level> \k'n-level'
\k<name+level> \k'name+level'
\k<name-level> \k'name-level'
Destine a group on the recursion level relative to the referring position.
ex 1.
/\A(?<a>|.|(?:(?<b>.)\g<a>\k<b>))\z/.match("reee")
/\A(?<a>|.|(?:(?<b>.)\g<a>\k<b+0>))\z/.match("reer")
\k<b+0> refers to the (?<b>.) on the same recursion level with it.
ex 2.
r = Regexp.compile(<<'__REGEXP__'.strip, Regexp::EXTENDED)
(?<element> \g<stag> \g<content>* \g<etag> ){0}
(?<stag> < \g<name> \s* > ){0}
(?<name> [a-zA-Z_:]+ ){0}
(?<content> [^<&]+ (\g<element> | [^<&]+)* ){0}
(?<etag> </ \k<name+1> >){0}
\g<element>
__REGEXP__
p r.match("<foo>f<bar>bbb</bar>f</foo>").captures
9. Subexp calls ("Tanaka Akira special") (* original function)
When we say "call a group," it actually means, "re-execute the subexp in
that group."
\g<n> \g'n' (n >= 1) call the nth group
\g<0> \g'0' call zero (call the total regexp)
\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<name> \g'name' call the group with the specified name
* Left-most recursive calls are not allowed.
ex. (?<name>a|\g<name>b) => error
(?<name>a|b\g<name>c) => OK
* Calls with a name that is assigned to more than one groups are not
allowed.
* 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<name>)(?i:(?<name>a)){0}/.match("A")
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. /..(?<name>..)../ (named group is used, no option)
(...) is treated as a non-capturing group.
numbered-backref/call is not allowed.
case 4. /..(?<name>..)../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_ONIGURUMA
(?m): dot (.) also matches newline
+ ONIG_SYNTAX_PERL and ONIG_SYNTAX_JAVA
(?s): dot (.) also matches newline
(?m): ^ matches after newline, $ matches before newline
A-2. Original extensions
+ hexadecimal digit char type \h, \H
+ named group (?<name>...), (?'name'...)
+ named backref \k<name>
+ subexp call \g<name>, \g<group-num>
A-3. Missing features compared with perl 5.8.0
+ \N{name}
+ \l,\u,\L,\U,\C
+ (?{code})
+ (??{code})
* \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), (?<!fixed-width-pattern)
+ add possessive quantifier. ?+, *+, ++
+ add operations in character class. [], &&
('[' must be escaped as an usual char in character class.)
+ add named group and subexp call.
+ octal or hexadecimal number sequence can be treated as
a multibyte code char in character class if multibyte encoding
is specified.
(ex. [\xa1\xa2], [\xa1\xa7-\xa4\xa1])
+ allow the range of single byte char and multibyte char in character
class.
ex. /[a-<<any EUC-JP character>>]/ 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 (?@<name>...)
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
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