Validating an IP with regex

Question

I need to validate an IP range that is in format 000000000 to 255255255 without any delimiters between the 3 groups of numbers. Each of the three groups that the final IP c

Answer 1

I would personally not use regex for this. I think it's easier to ensure that the string consists of 9 digits, split up the string into 3 groups of 3-digit numbers, and then check that each number is between 0 and 255, inclusive.

If you really insist on regex, then you could use something like this:

"([0-1][0-9][0-9]|2[0-4][0-9]|25[0-5]){3}"

The expression comprises an alternation of three terms: the first matches 000-199, the second 200-249, the third 250-255. The {3} requires the match exactly three times.