Character Escapes
Most of the important regular expression language operators are unescaped single characters. The escape character \ (a single backslash) signals to the regular expression parser that the character following the backslash is not an operator. For example, the parser treats an asterisk (*) as a repeating quantifier and a backslash followed by an asterisk (\*) as the Unicode character 002A.
The character escapes listed in this table are recognized both in regular expressions and in replacement patterns.
| Escaped character | Description |
|---|---|
| ordinary characters | Characters other than . $ ^ { [ ( | ) * + ? \ match themselves. |
| \a | Matches a bell (alarm) \u0007. |
| \b | Matches a backspace \u0008 if in a [] character class; otherwise, see the note following this table. |
| \t | Matches a tab \u0009. |
| \r | Matches a carriage return \u000D. |
| \v | Matches a vertical tab \u000B. |
| \f | Matches a form feed \u000C. |
| \n | Matches a new line \u000A. |
| \e | Matches an escape \u001B. |
| \040 | Matches an ASCII character as octal (up to three digits); numbers with no leading zero are backreferences if they have only one digit or if they correspond to a capturing group number. (For more information, see Backreferences.) For example, the character \040 represents a space. |
| \x20 | Matches an ASCII character using hexadecimal representation (exactly two digits). |
| \cC | Matches an ASCII control character; for example, \cC is control-C. |
| \u0020 | Matches a Unicode character using hexadecimal representation (exactly four digits). |
| \ | When followed by a character that is not recognized as an escaped character, matches that character. For example, \* is the same as \x2A. |
Note The escaped character \b is a special case. In a regular expression, \b denotes a word boundary (between \w and \W characters) except within a [] character class, where \b refers to the backspace character. In a replacement pattern, \b always denotes a backspace.