Video Tutorial on REGEX / Regular Expressions in linux Commandline

A regular expression, regex or regexp is, in theoretical computer science and formal language theory, a sequence of characters that define a search pattern.

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