Regex matching first part of domain name

Question

I am trying to match regex for the Fully Qualified Domain Name (fqdn) like this:

1.test02a-d.test.example.net
2.test02b-d.test.example.net
3.test03a.test.example.net
4.test03b.test.example.net
5.test04-d.test.example.net
6.test05.test.example.net

I tried this regex to get the first part of the fqdn:

[^.]+

Criteria: Here I need to get the list of fqdn that has alphabets 'a' or 'b' immediately after number in first part. As shown in the above example 1,2,3,4 matches this condition. i.e., test02a, test02a-d, test 02b and test02b-d

Fqdn 5 and 6 should be ignored as per the above criteria.

How to modify regex for matching this criteria?

Note: This should be used as REGEXP in Mysql and hence some direct javascript regexes didn't work. The solution should be applicable for both javascript and mysql.

@TomDoodler It matches whole first part of the string. I need to filter out the fqdn as per the criteria. Only 1,2,3,4 should get matched. — Ganesh Babu
– Ganesh Babu, Commented Aug 24, 2016 at 8:20

ltux · Accepted Answer · 2016-08-24 10:01:09Z

1

MySQL version:

^[^.]+[0-9]+[ab](-[^.]+)?[[:>:]]

JavaScript version:

^[^.]+[0-9]+[ab](-[^.]+)?\b

regex101.com doesn't support MySQL flavor regexp, so I only give the JavaScript version. test1bw.test.example.net is added as a test string.

[[:>]] is specific to MySQL. For JavaScript, \b should be used instead of [[:>]]. [[:>]] is a Zero-Length Assertion matching at the end of a word (position preceded by but not followed by an ASCII letter, digit, or underscore). \b matches at a position that is the start or end of a word.

MySQL doesn't support any shorthand character classes, so [[:digit:]] or [0-9] should be used instead of \d

edited Aug 24, 2016 at 10:01

answered Aug 24, 2016 at 8:33

ltux

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2 Comments

Ganesh Babu Over a year ago

Thanks. Your solution matches fqdn like this "test1bw.test.example.net". After number there should be only one alphabet. There can be hyphen after that alphabet. This should not be matched

ltux Over a year ago

@GaneshBabu Fixed. I suggest you add "test1bw.test.example.net" or some other test strings to your question to make your criteria clearer.

andii1997 · Accepted Answer · 2016-08-24 08:24:40Z

1

[a-z]+[0-9]+[ab](-d){0,1}(.test.example.net)

This Regex matches your first four domain names. The "[a-z]+" could also be specified with "(test)" You can test it on this site: http://regexr.com/

answered Aug 24, 2016 at 8:24

andii1997

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7 Comments

Ganesh Babu Over a year ago

Thanks.. It works now. How to ignore rest of the domain part. ie., instead of test.example.net, there may be any names

andii1997 Over a year ago

You can replace the ".test.example.net" in the regex with your domain, or otherwise you can just use [a-z]+[0-9]+[ab](-d){0,1}(.)+

Ganesh Babu Over a year ago

Thanks.. It works fine. But I am getting matched for examples of this form "test01.test90a-d.example.net". As per my case, I should match only first part of the domain name

andii1997 Over a year ago

[a-z]+[0-9]+[ab](-d){0,1}[.][^.]+[.][^.]+[.][^.]{2,4} would work, but is not a beautiful answer. Update: [a-z]+[0-9]+[ab](-d){0,1}[.][^.]+(.example.net) this would also work and i think it's better, but i'm not an expert.

Ganesh Babu Over a year ago

Thanks again.. But still your new solution didn't work.. :(

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SamWhan · Accepted Answer · 2016-08-24 08:29:38Z

0

Try

^[^.]+\d[ab][^.]*

It'll match, from the start of a line (^) any characters (more than one) not being a dot. Then there must be a digit followed by an a or a b, Optionally followed by another sequence of characters not being a dot.

See it here at regex101.

edited Aug 24, 2016 at 8:29

answered Aug 24, 2016 at 8:23

SamWhan

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Comments

BingBingBong · Accepted Answer · 2016-08-24 08:36:30Z

0

[a-zA-Z]+[\d]+[a-zA-Z]+.*

workes for me... try it here matches the whole domain.

[a-zA-Z]+[\d]+[a-zA-Z]+[-\w]*

matches only the first part of the domain.

edited Aug 24, 2016 at 8:36

answered Aug 24, 2016 at 8:28

BingBingBong

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6 Comments

Ganesh Babu Over a year ago

Thanks. But it didn't work for examples of this form "test01.test90a-d.example.net". I need a match for part before first dot.

BingBingBong Over a year ago

I´ll try to fix it

BingBingBong Over a year ago

what about (?<!.)[a-zA-Z]+[\d]+[a-zA-Z]+[-\w]* like here: regex101.com/r/pF3mG5/4

Ganesh Babu Over a year ago

Lookbehind is not supported in javascript

BingBingBong Over a year ago

Sorry, my mistake... this is not applicatable in js... looking for another solution...

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