| Metacharacter | Description |
| ^ | Matches the beginning of a line |
| $ | Matches the end of the line |
| . | Matches any character |
| \s | Matches whitespace |
| \S | Matches any non-whitespace character |
| * | Repeats a character zero or more times |
| *? | Repeats a character zero or more times(non-greedy) |
| + | Repeats a character one or more times |
| +? | Repeats a character one or more times(non-greedy) |
| [aeiou] | Matches a single character in the listed set |
| [^XYZ] | Matches a single character not in the listed set |
| [a-z0-9] | The set of characters can include a range |
| (pattern) | Defines a marked subexpression to extract |
| (?:pattern) | Defines a marked subexpression not to extract |
| x|y | Matches any one of several subexpressions |
| ? | Matches the preceding subexpression zero or one time |
| {n} | Matches the preceding subexpression n times |
| {n,} | Matches the preceding subexpression at least n times |
| {n,m} | Matches the preceding subexpression at least n and not more than m times |
| Assertion | Lookbehind | Lookahead |
|---|---|---|
| Positive | (?<=pattern) | (?=pattern) |
| Negative | (?<!pattern) | (?!pattern) |
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