Question

Can anybody help me with a regex? I have a string with digits like:

X024123099XYAAXX99RR

I need a regex to check if a user has inserted the correct information. The rule should have also a fallback that the input is checked from left to right.

For example, when tested these inputs should return TRUE:

X024

X024123099X

X024123099XYA

X024123099XYAAXX99R

And these ones should return FALSE:

XX024

X02412AA99X

X024123099XYAAXX9911

And so on. The regex must check for the correct syntax, beginning from the left.
I have something like that, but this seems not to be correct:

 \w\d{0,12}\w{0,6}\d{0,2}\w{0,2}

Big thanks for any help (I’m new to regex)

Answer 1

You could take OpenSauce’s regex and then hack it to pieces to allow partial matches:

^[A-Z](\d{0,9}$|\d{9}([A-Z]{0,6}$|[A-Z]{6}(\d{0,2}$|\d{2}([A-Z]{0,2}$))))

It’s not pretty but as far as I can tell it encodes your requirements.

Essentially I took each case of something like \d{9} and replaced it with something like (\d{0,9}$|\d{9}<rest of regex>).

I added ^ and $ because otherwise it will match substrings in an otherwise invalid string. For example, it will see an invalid string like XX024 and think it is okay because it contains X024.