RegExp Metacharacters.

RegexpMeta

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|  Metacharacter  |                                           Description                                                    |
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|        \        | Specifies the next character as either a special character, literal, back reference, or an octal escape. |
|        ^        |    Matches the position at the beginning of the input string.                                            |
|        $        |    Matches the position at the end of the input string.                                                  |
|        *        |    Matches the preceding subexpression zero or more times.                                               |
|        +        |    Matches the preceding subexpression one or more times.                                                |
|        ?        |    Matches the preceding subexpression zero or one time.                                                 |
|       {n}       |    Matches exactly n times, where n is a non-negative integer.                                           |
|       {n,}      |    Matches at least n times, n is a non-negative integer.                                                |
|      {n,m}      |    Matches at least n and at most m times, where m and n are non-negative integers and n <= m.           |
|        .        |    Matches any single character except "\n".                                                             |
|      [xyz]      |    A character set. Matches any one of the enclosed characters.                                          |
|       x|y       |    Matches either x or y.                                                                                |
|      [^xyz]     |    A negative character set. Matches any character not enclosed.                                         |
|      [a-z]      |    A range of characters. Matches any character in the specified range.                                  |
|      [^a-z]     |    A negative range characters. Matches any character not in the specified range.                        |
|        \b       |    Matches a word boundary, that is, the position between a word and a space.                            |
|        \B       |    Matches a nonword boundary. 'er\B' matches the 'er' in "verb" but not the 'er' in "never".            |
|        \d       |    Matches a digit character.                                                                            |
|        \D       |    Matches a non-digit character.                                                                        |
|        \f       |    Matches a form-feed character.                                                                        |
|        \n       |    Matches a newline character.                                                                          |
|        \r       |    Matches a carriage return character.                                                                  |
|        \s       |    Matches any whitespace character including space, tab, form-feed, etc.                                |
|        \S       |    Matches any non-whitespace character.                                                                 |
|        \t       |    Matches a tab character.                                                                              |
|        \v       |    Matches a vertical tab character.                                                                     |
|        \w       |    Matches any word character including underscore.                                                      |
|        \W       |    Matches any non-word character.                                                                       |
|       \un       |    Matches n, where n is a Unicode character expressed as four hexadecimal digits.                       |
|                 |    For example, \u00A9 matches the copyright symbol                                                      |
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