Regular expression metacharacters

Operator	Effect
.	Matches any single character.
?	The preceding item is optional and will be matched, at most, once.
*	The preceding item will be matched zero or more times.
+	The preceding item will be matched one or more times.
{N}	The preceding item is matched exactly N times.
{N,}	The preceding item is matched N or more times.
{N,M}	The preceding item is matched at least N times, but not more than M times.
-	represents the range if it's not first or last in a list or the ending point of a range in a list.
^	Matches the empty string at the beginning of a line; also represents the characters not in the range of a list.
$	Matches the empty string at the end of a line.
\b	Matches the empty string at the edge of a word.
\B	Matches the empty string provided it's not at the edge of a word.
\<	Match the empty string at the beginning of word.
>	Match the empty string at the end of word.
?(list)	Matches zero or one occurrence of the given patterns.
*(list)	Matches zero or more occurrences of the given patterns.
+(list)	Matches one or more occurrences of the given patterns.
@(list)	Matches one of the given patterns.
!(list)	Matches anything except one of the given patterns.

^ – Match only if the Following is at the Beginning of the Line
$ – Match only if the Previous is at the End of the Line
? – Match the Previous 0 or 1 times (makes it optional)
. – Match any Single Character
- – Match the Previous 0 or More Times
- – Match the Previous 1 or More Times
(x) – Matches x and Remembers the match to be called using $1
(?:x) – Matches x but does Not remember the match
x(?=y) – Matches x Only if it is followed by y
x(?!y) – Matches x only if it is NOT followed by y
x|y – Matches x or y
[xyz] – Matches any character enclosed in the Brackets. Note: This matches X, or Y, or Z; it doesn’t match the string “xyz”.
^xyz – Matches any character Except for those listed in the Brackets.
\ – “Escape” special characters. Thus \? literally matches ? not the Syntax Rule of “previous is option”.
\d \w \s – Matches and Digit (number), Alphabetic Character (letter) or White Space (space bar) respectively.
\D \W \S – Matches everything But a Digit, Character, or White Space respectively.

results matching ""