1. Syntax elements
- \ escape (enable or disable meta character meaning)
+ \ escape (enable or disable meta character)
| alternation
(...) group
[...] character class
2. Characters
- \t horizontal tab (0x09)
- \v vertical tab (0x0B)
- \n newline (0x0A)
- \r return (0x0D)
- \b back space (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)
- \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 is effective in character class [...] only)
+ \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)
+ \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)
3. Character types
Unicode:
General_Category -- (Letter|Mark|Number|Connector_Punctuation)
- \W non word char
+ \W non-word char
\s whitespace char
-- Paragraph_Separator
-- Space_Separator
- \S non whitespace char
+ \S non-whitespace char
\d decimal digit char
Unicode: General_Category -- Decimal_Number
- \D non decimal digit char
+ \D non-decimal-digit char
\h hexadecimal digit char [0-9a-fA-F]
- \H non hexadecimal digit char
+ \H non-hexdigit char
Character Property
? 1 or 0 times
* 0 or more times
+ 1 or more times
- {n,m} at least n but not more than m times
+ {n,m} at least n but no more than m times
{n,} at least n times
- {,n} at least 0 but not more than n times ({0,n})
+ {,n} at least 0 but no more than n times ({0,n})
{n} n times
reluctant
{n,}? at least n times
{,n}? at least 0 but not more than n times (== {0,n}?)
- possessive (greedy and does not backtrack after repeated)
+ possessive (greedy and does not backtrack once match)
?+ 1 or 0 times
*+ 0 or more times
^ beginning of the line
$ end of the line
\b word boundary
- \B not word boundary
+ \B non-word boundary
\A beginning of string
\Z end of string, or before newline at the end
\z end of string
6. Character class
- ^... negative class (lowest precedence operator)
+ ^... negative class (lowest precedence)
x-y range from x to y
[...] set (character class in character class)
- ..&&.. intersection (low precedence at the next of ^)
+ ..&&.. 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 '[', '-', ']' as a normal character
- in a character class, you should escape these characters by '\'.
+ * If you want to use '[', '-', or ']' as a normal character
+ in character class, you should escape them with '\'.
POSIX bracket ([:xxxxx:], negate [:^xxxxx:])
(?imx-imx) option on/off
i: ignore case
- m: multi-line (dot(.) match newline)
+ m: multi-line (dot (.) also matches newline)
x: extended form
(?imx-imx:subexp) option on/off for subexp
- (?:subexp) not captured group
- (subexp) captured group
+ (?:subexp) non-capturing group
+ (subexp) capturing group
(?=subexp) look-ahead
(?!subexp) negative look-ahead
(?<=subexp) look-behind
(?<!subexp) negative look-behind
- Subexp of look-behind must be fixed character length.
- But different character length is allowed in top level
- alternatives only.
+ Subexp of look-behind must be fixed-width.
+ But top-level alternatives can be of various lengths.
ex. (?<=a|bc) is OK. (?<=aaa(?:b|cd)) is not allowed.
- In negative-look-behind, captured group isn't allowed,
- but shy group(?:) is allowed.
+ In negative look-behind, capturing group isn't allowed,
+ but non-capturing group (?:) is allowed.
(?>subexp) atomic group
- don't backtrack in subexp.
+ no backtracks in subexp.
(?<name>subexp), (?'name'subexp)
define named group
- (All characters of the name must be a word character.)
+ (Each character of the name must be a word character.)
- Not only a name but a number is assigned like a captured
+ Not only a name but a number is assigned like a capturing
group.
- Assigning the same name as two or more subexps is allowed.
+ Assigning the same name to two or more subexps is allowed.
In this case, a subexp call can not be performed although
the back reference is possible.
10. Captured group
- Behavior of the no-named group (...) changes with the following conditions.
+ 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 captured group.
+ (...) is treated as a capturing group.
case 2. /.../g (named group is not used, 'g' option)
- (...) is treated as a no-captured group (?:...).
+ (...) is treated as a non-capturing group (?:...).
case 3. /..(?<name>..)../ (named group is used, no option)
- (...) is treated as a no-captured group (?:...).
+ (...) 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 captured group.
+ (...) is treated as a capturing group.
numbered-backref/call is allowed.
where
-----------------------------
-A-1. Syntax depend options
+A-1. Syntax-dependent options
+ ONIG_SYNTAX_RUBY
- (?m): dot(.) match newline
+ (?m): dot (.) also matches newline
+ ONIG_SYNTAX_PERL and ONIG_SYNTAX_JAVA
- (?s): dot(.) match newline
- (?m): ^ match after newline, $ match before newline
+ (?s): dot (.) also matches newline
+ (?m): ^ matches after newline, $ matches before newline
A-2. Original extensions
+ subexp call \g<name>, \g<group-num>
-A-3. Lacked features compare with perl 5.8.0
+A-3. Missing features compared with perl 5.8.0
+ \N{name}
+ \l,\u,\L,\U, \X, \C
+ add character property (\p{property}, \P{property})
+ add hexadecimal digit char type (\h, \H)
+ add look-behind
- (?<=fixed-char-length-pattern), (?<!fixed-char-length-pattern)
+ (?<=fixed-width-pattern), (?<!fixed-width-pattern)
+ add possessive quantifier. ?+, *+, ++
+ add operations in character class. [], &&
('[' must be escaped as an usual char in character class.)
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 incomplete left brace as an usual string.
+ + 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 numbered character.
+ + Ignore case option is effective to escape sequence.
ex. /\x61/i =~ "A"
- + In the range quantifier, the number of the minimum is omissible.
+ + In the range quantifier, the number of the minimum is optional.
/a{,n}/ == /a{0,n}/
- The simultaneous abbreviation of the number of times of the minimum
- and the maximum is not allowed. (/a{,}/)
- + /a{n}?/ is not a non-greedy operator.
+ 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 cause error.
+ + invalid back reference is checked and raises error.
/\1/, /(a)\2/
- + Zero-length match in infinite repeat stops the repeat,
+ + 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. Disabled functions by default syntax
+A-5. Features disabled in default syntax
+ capture history
projects / onig / commitdiff