Regex to match code with fixed country code and variable wildcard usage

Question

I need to implement a regex which cover several requirements. These are the following:

• A length restriction to max 8 chars should be done (with or without wildcard). In any case the code is never longer than 8 chars.
• When wildcard is given also lower then 8 digits is allowed. Without wildcard exactly 8 digits are needed.
• allowed characters are: 0-9A-Za-z* (all digits, all chars, asterix as wildcard)
• pure wildcard must be possible
• else the first two digits must contain a 2 chars country code (alpha-numeric) and then only number or wildcards are allowed.
• after country code wildcard can be used at any place (in the middle, at the end, mutliple asterix/wildcards after each other also allowed)

I tried many things so far and thought about Lookahead/Lookbehind because of the asterix and the max. length. My latest state which covers the most of the requirements is the following:

^([A-Za-z]{2}[0-9*]{0,6}|\*)$

check the live demo with right/wrong combo

But in this example a code without asterix/wildcard is possible with less than 8 chars -> that's wrong.

Thanks a lot for any help in advance :)

Answer 1

You can use

^(?!.*\*\*$)(?!.{9})(?:[A-Za-z]{2}(?:\d*(?:\*\d*)+|\d{6})|\*)$

See the regex demo.

Details:

• ^ - start of string
• (?!.*\*\*$) - no two ** at the end of string allowed
• (?!.{9}) - the string must contain less than 9 chars other than line break chars
• (?:[A-Za-z]{2}(?:\d*(?:\*\d*)+|\d{6})|\*) - one of the two alternatives:
  • [A-Za-z]{2}(?:\d*(?:\*\d*)+|\d{6}) - two letters and then either six digits or zero or more digits followed with one or more sequences of an asterisk and zero or more digits
  • | - or
  • \* - an asterisk
• $ - end of string.