Question

I would like to match positive and negative numbers (no decimal or thousand separators) inside a string using .NET, but I want to match whole words only.
So if a string looks like

redeem: -1234
paid: 234432

then I’d like to match -1234 and 234432

But if text is

LS022-1234-5678
FA123245

then I want no match returned. I tried

\b\-?\d+\b

but it will only match 1234 in the first scenario, not returning the “-” sign.

Any help is appreciated. Thank you.

Answer 1

Well, I’m sure this is far from perfect, but it works for your examples:

(?<=\W)-?(?<!\w-)\d+

If you want to allow underscores just before the number, then I’d use this modification:

(?i)(?<=[^a-z0-9])-?(?<![a-z0-9]-)\d+

Let me know of any issues and I’ll try and help. If you’d like me to explain either of them, let me know that too.

EDIT

To only match if there is a space or tab just before the number / negative sign (as noted in the comment below), this could be used:

(?<=[ \t])-?\d+

Note that it will match e.g. on the first number series of a telephone number, time or date value, and will not match if the number is at the beginning of the line (after a newline) – make sure this is what you intend 😀