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regexregex-lookarounds

Regex to capture optional characters

I want to pull out a base string (Wax) or (noWax) from a longer string, along with potentially any data before and after if the string is Wax. I'm having trouble getting the last item in my list below (noWax) to match.

Can anyone flex their regex muscles? I'm fairly new to regex so advice on optimization is welcome as long as all matches below are found.

What I'm working with in Regex101:

/(?<Wax>Wax(?:Only|-?\d+))/mg
Original string need to extract in a capturing group
Loc3_341001_WaxOnly_S212 WaxOnly
Loc4_34412-a_Wax4_S231 Wax4
Loc3a_231121-a_Wax-4-S451 Wax-4
Loc3_34112_noWax_S311 noWax
Solution

  • Here is one way to do so, using a conditional:

    (?<Wax>(no)?Wax(?(2)|(?:Only|-?\d+)))

    See the online demo.

    • (no)?: Optional capture group.
    • (? If.
      • (2): Test if capture group 2 exists ((no)). If it does, do nothing.
      • |: Or.
      • (?:Only|-?\d+)