regular expression

RegularExpression.md

Regular Expression

Used to match the string in a sequence of chars. Regular expression is case sensitive.

Searching for literal Chars

• this is the simplest of all searches. to search ABC just do ABC.

Searching for reserved chars

• there are some reserved keywords in Regular Expression which has special meaning. like . . so to search for a . we can not just write it like that. we need to escape it. like \. .
• other special chars in regular expression are - .[{()^$|?*+

Using complex patterns

Pattern	Description
.	Any Character Except New Line
\d	Digit (0-9)
\D	Not a Digit (0-9)
\w	Word Character (a-z, A-Z, 0-9, _)
\W	Not a Word Character
\s	Whitespace (space, tab, newline)
\S	Not Whitespace (space, tab, newline)
\b	Word Boundary
\B	Not a Word Boundary
^	Beginning of a String
$	End of a String
[]	Matches Characters in brackets
[^ ]	Matches Characters NOT in brackets
|	Either Or
( )	Group

Quantifiers:

Pattern	Description
*	0 or More
+	1 or More
?	0 or One
{3}	Exact Number
{3,4}	Range of Numbers (Minimum, Maximum)

Reference video