Perl Regex return named groups in capture Group one-CodePudding

I try to get a regex which returns the match in the first capture group.

The Application where I put the regex in can only use the first capture Group.

Each regex on it's own is working, but i can't combine these two in a way that the output is always in the first capture group

Input 1:

Event: Started Flapping

Regex 1:

^Event: (\S  Flapping)

Output 1:

Started Flapping

Input 2:

Event: CRIT -> OK

Regex 2:

^Event:\s \S \s \S \s (\S )

Ouput 2:

OK

The Regex i tried (?:^Event:\s \S \s \S \s (?P<service>\S )$|^Event: (?P<flap>Started Flapping)|((?P=service)|(?P=flap)))

CodePudding user response：

^Event:\s (?|\S \s \S \s (\S )|(Started Flapping))$
# or, to factor in \S \s :
^Event:\s (?|(?:\S \s ){2}(\S )|(Started Flapping))$

See the regex demo. Details:

^ - start of string
Event: - a fixed string
\s - one or more whitespaces
(?| - start of a branch reset group:
- \S \s \S \s - two occurrences of one or more non-whitespaces followed with one or more whitespaces
- (\S ) - Group 1: one or more non-whitespaces
| - or
- (Started Flapping) - Group 1: Started Flapping fixed string
) - end of the branch reset group
$ - end of string.