Cant seem to get the skiplist to work

[brackebuschtino]

Yep, in fact a lookbehind is the more appropriate selection in this case since the part of the string your most interested in is at the end. Less expensive as well.

Unfortunately this doesn't seem to allow for grouping or appending an additional group that might exist. At least it didn't work for me with:

rx .*(?<!-PublisherX(_int)?)$

rx .*(?<!-(PublisherX|OtherY))$

[DayCuts]

Learned something when trying to figure out why (_int)? worked in a look-ahead but not a look-behind. The answer is that in almost all regex flavors (language implementations) a look-behind must be a fixed-width expression. Not only does this mean you can not include ? + *, which rules out anything like (_int)?, but you also can not include optionals of different lengths like (pub|longpublisherame). Ultimately this means that a look-behind is not a viable option for your purposes unless the developing language of the program is using it is .NET or ABA.

Now onto a solution... first of all one reason optionals were not working for you is that you are forgetting part of the expression. The modifiers and anchors are important. I did come up with a working solution using a look-behind, but my test list used equal length publisher names. It failed thereafter due to the fixed-length requirement but here it is anyway...

(?im)(?(DEFINE)(?<publist>(?:publisher1|publisher2)))^.+(?(?<=_int$)(?<!-(?&publist)_int)|(?<!-(?&publist))$)

An updated version of the original pattern...

(?im)^(?!.+-(?:publisher1|publisher2)(?:_int)?$).+$

[brackebuschtino]

Thanks alot for this lession. It turns out that using lookarounds is very tricky. I would never been able to adopt this pattern on my own.