When changing host value using transforms.conf, how do I set the host value to something based on a regex?

[dfetcher]

I'm very new to Splunk. I'm trying to use transforms.conf and props.conf to set the host value to something based on a regex. Every time I try it, the host value is always set to $1.

This is my transforms.conf

[setHost]
DEST_KEY = MetaData:Host
SOURCE_KEY = MetaData:Source
REGEX = webserver\d{0,2}-\d{0,3}
FORMAT = host::"$1"

This is my props.conf

[iis]
TRANSFORMS-setHost = setHost

The source that it's coming from looks like this /var/logs/webserver01-003/blah.log

How do I get this to work?

Thank you.

[FrankVl · Accepted solution]

Or much simpler: set host_segment = 3 in inputs.conf and you can forget about that whole TRANSFORMS stuff 🙂

[martin_mueller]

Remove the double quotes around $1 in your FORMAT, and add a capturing group to your REGEX around whatever you want the host value to be. $1 refers to the first capturing group, without a capturing group there's nothing to refer to.