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. |
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\a |
Matches a bell (alarm) \u0007. |
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\b |
Matches a backspace \u0008 if in a [] character class; otherwise, see the note following this table. |
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\t |
Matches a tab \u0009. |
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\r |
Matches a carriage return \u000D. |
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\v |
Matches a vertical tab \u000B. |
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\f |
Matches a form feed \u000C. |
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\n |
Matches a new line \u000A. |
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\e |
Matches an escape \u001B. |
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\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 |
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\x20 |
Matches an ASCII character using hexadecimal representation (exactly two digits). |
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\cC |
Matches an ASCII control character; for example, |
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\u0020 |
Matches a Unicode character using hexadecimal representation (exactly four digits).
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\ |
When followed by a character that is not recognized as an escaped character, matches that character. For example, \* is the same as \x2A. |
.gif) Note |
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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. |