Optimize a regex validating a version string

Question

I develop an application which installs updates. These updates have a version id (this version id is created as a part of the application and the format is a fixed requirement) and I use a regex to parse/validate their id. Each group must be separated by a dot. The id must have 2 digits in the first group, one or two digits in the second group and the third group and at least one digit in the last group.

The regex I use is the following:

^[0-9]{2}\.[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,}$

The regex works like expected but when I look at it I have a feeling telling me that I can make it better, smarter and and and and ...

Should I stay with this solution or how would you make it better?

The regex should work with the .NET-Framework Regex class.

Answer 1

Since the second and third segment are similar, you can put them in a non-capturing group with quantifier.

If you allow/want the first digit to be \$ 0 \$ in your first group, the expression is ok as it is. Otherwise, you can restrict the first digit to be [1-9].

You can have + quantifier instead of {1,} as they are essentially the same :)

^[0-9]{2}(?:\.[0-9]{1,2}){2}\.[0-9]+$

and for unpadded version matches:

^[1-9][0-9](?:\.[0-9]{1,2}){2}\.[0-9]+$