Regex Literal and Special Characters

This section describes the regular expression syntax for referring to literal characters, special characters, nonprintable characters (such as a tab or a newline), and special character escaping.

Literal Characters

The most basic form of pattern matching is the match of literal characters. If the regular expression is

foo

and the input string is

foo

, the match will succeed because the strings are identical.

Special Characters

Certain characters are reserved for special use in regular expressions. These special characters are called metacharacters. If you want to use special characters as literal characters, you must escape them.

Character Name	Character	Reserved For
opening bracket	[	Start of a character class
closing bracket	]	End of a character class
hyphen	-	Character ranges within a character class
backslash	\	General escape character
caret	^	Beginning of string, negating of a character class
dollar sign	$	End of string
period	.	Matching any single character
pipe	\|	Alternation (OR) operator
question mark	?	Optional quantifier, quantifier minimizer
asterisk	*	Zero or more quantifier
plus sign	+	Once or more quantifier
opening parenthesis	(	Start of a subexpression group
closing parenthesis	)	End of a subexpression group
opening brace	{	Start of min/max quantifier
closing brace	}	End of min/max quantifier

Escaping Special Characters

You can use these methods to treat a special character as a literal (ordinary) character:

Precede the special character with a

\

(backslash character). Example: to specify an asterisk as a literal character instead of a quantifier, use

\*

.

Enclose the special characters within

\Q

(starting quote) and

\E

(ending quote). Everything between

\Q

and

\E

is then treated as literal characters.

To escape literal double-quotes in a

REGEX()

expression, double the double-quotes (

""

). Example: to extract the inches portion from a

height

field where example values are

6'2"

,

5'11"

:

REGEX([height], "\'(\d)+""$")

NonPrinting Characters

You can use special character sequence constructs to specify nonprintable characters in a regular expression. Some of the most commonly used constructs are:

Construct	Matches
\n	newline character
\r	carriage return character
\t	tab character
\f	form feed character