| ( ) |
Define Capturing Groups
Allows a group of characters to be treated as a single unit
Capturing Groups are numbered according to the number of opening
parentheses left to right.
|
| [ ] |
Defines character class |
| \n |
Back reference captured group n
Escape Character when used by itself \
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| | |
OR |
| && |
Intersection Operator |
| . |
Any single character
May or may not match line terminators |
| , |
Bound number of matches |
| Quantifiers |
| ? |
Match once or not at all
Also append to quantifier to create Reluctant Quantifier
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| * |
Match zero or more times |
| + |
Match one or more times
Also append to quantifier to create Possessive Quantifier
|
| {n} |
Match pattern n times |
| Boundary Matchers |
| ^ |
Match beginning of a line
Negation when used in character class
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| $ |
Match end of a line |
| \b |
Word boundary |
| \B |
Non-word boundary |
| \A |
Beginning of input |
| \G |
End of previous match |
| \Z |
End of input but before final terminator, if any |
| \z |
End of input |
| Predefined Character Ranges |
| \d |
A single digit [0-9] |
| \D |
A single non-digit [^0-9] |
| \s |
A single whitespace character [ \t\n\x0B\f\r] |
| \S |
A single non-whitespace character [^\s] |
| \w |
A single word character [a-zA-Z_0-9] |
| \W |
A single non-word character [^\w] |
| Embedded Flag Expressions |
| (?i) |
Case Insensitive |
| (?x) |
Comments - whitespace and # until end of line ignored |
| (?m) |
Multi line |
| (?s) |
Dot "." matches line terminators too |
| (?u) |
Unicode |
| (?d) |
Unix lines |
Precede meta character with backslash to have it be treated like
an ordinary character
Or enclose it within \Q and \E (start quote, end quote)
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