Regex Numbers that are not proceed by a specific string

Question

I have this regex:

(?<!FY)([0-9]{1,4}\.|)(?<!VAC)?([0-9]{1,4})?([A-Z])?(-)([0-9]{1,4})(\.[0-9]{1,2})?(\:[0-9]{1,2})?(\.[0-9]{1,2})?(?!.*?\<\/a\>)

and the following string:

Examine 58.1-609.6 brother prudent add day ham. FY 22-23 stairs now 58.1-439.12:02 oppose hunted become

I want to get:

• 58.1-609.6

• 58.1-439.12:02

But not: FY 22-23

Answer 1

To match those numbers in the question, you might use:

(?<!\b(?:FY|VAC)\s*)\b[0-9]{1,4}\.[0-9]-[0-9]{1,4}\.[0-9]{1,2}(?::[0-9]{1,2})?\b

Explanation

• (?<! Negative lookbehind, assert what is to the left is not
  • \b(?:FY|VAC)\s* match either FY or VAC followed by optional whitspace chars
• ) Close the lookahead
• \b[0-9]{1,4}\.[0-9]-[0-9]{1,4} A word boundary, then match 1-4 digits . digit - 1-4 digits
• \.[0-9]{1,2} Match . 1-2 digits
• (?::[0-9]{1,2})? Optionally match : and 1 or 2 digits
• \b A word boundary

See a .NET regex demo .

Then you can extend the pattern to assert not a closing anchor tag to the right with (?.?*?\<\/a\>) or other rules that you want like optional chars [AZ]?