I want to create a regular expression for DNS. My requirement is that the valid DNS should be: www.x.y www.t.x.y www.s.t.x.y Only 4 dots( . ) are allowed. I have tried this regular expression but its not working. Please suggest. ^[a-zA-Z0-9]+.[a-zA-Z0-9]+.[a-zA-z0-9]+.[a-zA-z0-9]$

A very simple regex could be something along ^www\.[a-zA-Z0-9]+\.[a-zA-Z0-9]+(\.[a-zA-Z0-9]+(\.[a-zA-Z0-9]+)?)?$ Three points: the point ( . ) is a special character and must be escaped ( \. ) we need optional clauses for the last two sections. your examples start with www , so you need to include this in order to use the start mark ( ^ )

javaregex

anonymous

Reputation: 244

regular expression for the address of domain name server

I want to create a regular expression for DNS.

My requirement is that the valid DNS should be:

www.x.y
www.t.x.y
www.s.t.x.y

Only 4 dots(.) are allowed. I have tried this regular expression but its not working. Please suggest.

^[a-zA-Z0-9]+.[a-zA-Z0-9]+.[a-zA-z0-9]+.[a-zA-z0-9]$

Upvotes: 1

Answers (4)

Ran Adler

Reputation: 3711

try this link

Regular expression to match DNS hostname or IP Address?

Regular Expression Test Page

http://www.regexplanet.com/advanced/java/index.html

Upvotes: 1

Matten

Reputation: 17621

A very simple regex could be something along

^www\.[a-zA-Z0-9]+\.[a-zA-Z0-9]+(\.[a-zA-Z0-9]+(\.[a-zA-Z0-9]+)?)?$

Three points:

the point (.) is a special character and must be escaped (\.)
we need optional clauses for the last two sections.
your examples start with www, so you need to include this in order to use the start mark (^)

Upvotes: 1