Need help with a regular expression

abefroman · 05-28-2008, 03:11 PM

How can I match at least 1 non-digit, followed by 4 digits with a perl compatible regular expression?

I have:
\D{1}\d{4}
but thats matching 4 digits, 5 digits, 6 digits, etc.

osor · 05-28-2008, 03:53 PM

Quote:

Originally Posted by abefroman

but thats matching 4 digits, 5 digits, 6 digits, etc.

Of course it does. This is because one non-digit followed by 5 digits is also one non-digit followed by 4 digits. If you were capturing the expression, you would notice that only the four digits you want will be captured.

Otherwise you want to revise your criteria. What it seems you want is one non-digit, followed by 4 digits, with the proviso that if you look ahead, there will be 0 or more non-digits. So

Code:

\D\d{4}(?=\D*)

You don’t really need the look-ahead unless your are capturing, so this will work just as well in a simple truth test:

Code:

\D\d{4}\D*

abefroman · 05-28-2008, 09:17 PM

Thanks!