Regular Expressions

gistfile1.txt

# Regular Expressions 

.       - 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)


------------------------------------E X A M P L E S --------------------------------------

regex = [A-Za-z0-9\.+_-~-]+@[A-Za-z.]+\.[A-Za-z]{2,3}

read it as: check for 1 or more of  [A-Za-z0-9\.+_-~-] followed by an @ and then following by 1 or more of [A-Za-z.] following by a dot and then 2 or 3 characters of [A-Za-z]

Internet email addresses must include only RFC-compliant characters, which include:
Numbers 0-9.
Uppercase letters A-Z.
Lowercase letters a-z.
Plus sign +
Hyphen -
Underscore _
Tilde ~


Valid Emails

william@test.com
william.pourmajidi@gmail.com
william+pourmajidi@gmail.com
william-pourmajidi@gmail.com
william_pourmajidi@gmail.com
william~pourmajidi@gmail.com
william@gmail.com 
william@gmail.ai
william.1982@gmail.com
1982.william@gmail.com
william.pourmajidi@subdomain.gmail.com 


Invalid Emails

william.pourmajidi.gmail.com
william@gmail
william@gmail.c