Regular expression to match a percentage with decimal?

Question

I\'m attempting to build a regular expression (.NET) to match a percentage with 4 decimal places. The 4 decimal places are required. The range looks like:

0.         


        

Answer 1

I would do something like this:

^((([0-9]|[1-9]\d)\.\d{4})|100\.0000)$

Proof

Answer 2

Just treat the 100.0000 possibility as a separate case. It's easy to match that (100\.0000), and it's easy to match the rest ([1-9]?\d\.\d{4}), so with the two as alternates you get:

^(100\.0000|[1-9]?\d\.\d{4})$

(Assuming you want it to be the whole text, otherwise leave out the ^ and the $.

Answer 3

See it in action:

^(0|[1-9]\d?)\.\d{4}|100\.0000$

Matches:

0.0001
100.0000
42.4214
1.0000

Doesn't match:

100.0135
042.4214
001.0000
000.0000
1000.0000
2000.0000
300.0000