Extract nums from str by count

How to get a 4-digit number from a given string using Regex?

Given the string something/word/statement-fm-4512-co-km458, how can we use Regex to get the 4-digit number (4512) that is not always after fm- or before -co?

The following Regex pattern can be used to extract the 4-digit number from the given string:



  • (?<=fm-)\d{4} matches any 4-digit number that comes after fm- using a positive lookbehind (?<=fm-).
  • | or operator is used to match either the first or second pattern.
  • (?<=-)\d{4}(?=-co) matches any 4-digit number that is preceded by a - and followed by -co using positive lookarounds (?<=-) and (?=-co) respectively.