CODEWITHSUNDEEP
regex
Yusuf
Yusuf

Reputation: 119

Reg Ex to match host name - different lenghts

I am looking for a regex to give just the hostname from a FQDN.

E.g. I want just "host" from "host.company.com".

I've come up with this so far:

^(.{4}).*

However, because some devices stored in the CMDB dont have the full FQDN, it can also catch devices with no dot.

What I am struggling now with is when the hostname has different lengths.

Upvotes: 0

Views: 247

Answers (2)

Zsolt Botykai
Zsolt Botykai

Reputation: 51603

^([^.]+)(\.|$| )

Should capture it (and I'm using it this way, as it provides a non-greedy regex supported by most implementations).

Upvotes: 0

daniel gratzer
daniel gratzer

Reputation: 53881

So since we are trying to get everything before the first period we do:

^(.*?)\.

The question mark indicates to match as little as possible and we escape the . to have it represent an actual dot.

Which returns "host" when matched against host.company.com.

To account for the fact that there may not be a period we use the | modifier.

^(.*?)(\.|$)

Where $ will match the end of the line.

However if your not sure whether you need a period or not, I would say to not use a regex, instead use a find function or algorithm on the string, this will be more practical and robust.

Upvotes: 1

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