Regular Expressions 101

Explanation

Pro

^start of line

Group 1([[:alpha:]]+)

Character Class[[:alpha:]]+

+matches at least one character from the set below:

[:alpha:]an alphabetic character [a-zA-Z]

Group 2(.?)

.?optionally matches any character (except for line terminators)

Group 3([[:alpha:]]*)

Character Class[[:alpha:]]*

*matches any number of characters from the set below:

[:alpha:]an alphabetic character [a-zA-Z]

Group 4(\.([[:alpha:][:digit:]]*))?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 5([[:alpha:][:digit:]]*)

Character Class[[:alpha:][:digit:]]*

*matches any number of characters from the set below:

[:alpha:]an alphabetic character [a-zA-Z]

[:digit:]a digit [0-9]

@the literal @ (64₁₀ / 100₈ / 40₁₆)

Character Class[[:alpha:]]*

*matches any number of characters from the set below:

[:alpha:]an alphabetic character [a-zA-Z]

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[[:alpha:]]{3,7}

{3,7}matches between 3 and 7 characters from the set below:

[:alpha:]an alphabetic character [a-zA-Z]

\ban ASCII word boundary

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

^([[:alpha:]]+)(.?)([[:alpha:]]*)(\.([[:alpha:][:digit:]]*))?@[[:alpha:]]*\.[[:alpha:]]{3,7}\b

New

//Valid
customer@yahoo.com 
customer.name@yahoo.com 
customer_name@yahoo.com 
customer.name.name2@yahoo.com 

//Invalid
customer@yahoo..com
#customer@yahoo.com 
cu$$tomer@yahoo.com 
customer@yahoo.c 
customer@yahoo.commmmmmm 
customer.name.#name2@yahoo.com

Extraction

//Valid
customer@yahoo.com 
customer.name@yahoo.com 
customer_name@yahoo.com 
customer.name.name2@yahoo.com 

//Invalid
customer@yahoo..com
#customer@yahoo.com 
cu$$tomer@yahoo.com 
customer@yahoo.c 
customer@yahoo.commmmmmm 
customer.name.#name2@yahoo.com