Regular Expressions use a backslash (\) to signify the following character has been escaped - something which is done for multiple purposes. Previously we saw how \s could be used to specify white-space, similarly other characters can be used to specify other characters.
- \s
- Whitespace (such as the character produced by pressing the spacebar)
- \S
- Non-whitespace
- \d
- Matches a digit (0-9)
- \D
- Matches anything that isn't a digit
- \x
- Matches a hexadecimal number
- \O
- Matches an octal digit
- \w
- Matches a word character (any alphanumeric character or an underscore)
- \W
- Matches any non-word character
- \c
- Matches a control character
Similar to the above escaped characters that are used for ranges of characters (of a type), there are other special characters that are used to symbolise other things such as a newline.
- \n
- Matches a new line
- \t
- Matches a tabstop
- \r
- Matches a carriage return
- \v
- Matches a vertical tab character
- \xxx
- Matches the octal digit xxx
- \xhh
- Matches the hexadecimal digit hh
- \f
- Matches a form feed
The following characters must be escaped when used: ^, (, ), , ., *, [, ], {, }, \, |, $, ?, +
