Regex to match 2 digits, optional decimal, two digits

Question

Hi,

I've spent half an hour trying to get this, maybe someone can come up with it quickly.

I need a regular expression that will match one or two digits, followed by an optional decmial point, followed by one or two digits.

For example, it should match these strings in their entirety:

3
33
.3
.33
33.3
33.33

and NOT match anything with more than 2 digits before or after the decmial point.

Thank you, Eric

Answer 1

You mentioned that you want the regex to match each of those strings, yet you previously mention that the is 1-2 digits before the decimal?

This will match 1-2 digits followed by a possible decimal, followed by another 1-2 digits but FAIL on your example of .33

\d{1,2}\.?\d{1,2}

This will match 0-2 digits followed by a possible deciaml, followed by another 1-2 digits and match on your example of .33

\d{0,2}\.?\d{1,2}

Not sure exactly which one you're looking for.

Answer 2

EDIT: Changed to fit other feedback.

I understood you to mean that if there is no decimal point, then there shouldn't be two more digits. So this should be it:

\d{0,2}(\.\d{1,2})?

That should do the trick in most implementations. If not, you can use:

[0-9]?[0-9]?(\.[0-9][0-9]?)?

And that should work on every implementation I've seen.

Answer 3

^\d{0,2}\.?\d{1,2}$

Answer 4

To build on Lee's answer, you need to anchor the expression to satisfy the requirement of not having more than 2 numbers before the decimal.

If each number is a separate string, you can use the string anchors:

^\d{0,2}(\.\d{1,2})?$

If each number is within a string, you can use the word anchors:

\b\d{0,2}(\.\d{1,2})?\b

Answer 5

(?<![\d.])(\d{1,2}|\d{0,2}\.\d{1,2})?(?![\d.])

Matches:

• Your examples
• 33.

Does not match:

• 333.33
• 33.333

Answer 6

^(\d{0,2}\.)?\d{1,2}$

"\d{1,2}$" matches a 1-2 digit number with nothing after it (3,33,etc), "(\d{0,2}.)?" matches optionally a number 0-2 digits long followed by a period (3., 44., ., etc). Put them together and you've got your regex.

Answer 7

A previous answer is mostly correct, but it will also match the empty string. The following would solve this.

^([0-9]?[0-9](\.[0-9][0-9]?)?)|([0-9]?[0-9]?(\.[0-9][0-9]?))$