pcre - Regex to match characters to the right of a colon

I'm stuck on a regex. I'm trying to match words in any language to the right of a colon without matching the colon itself.

The basic rule:

• For a line to be valid, it must not begin with or contain any characters outside of [a-z0-9_] until after :.




• Any characters to the right of : should match as long as the line begins with the set of characters defined above.

For instance, given a string such as these:

this string should not match

bob_1:Hi. I'm Bob. I speak русский and this string should match  


alice:Hi Bob. I speak 한국어 and this string should also match

http://example.com - would prefer to not match URLs

This string:should not match because no spaces or capital letters are allowed left of the colon

Only 2 of the 5 strings above need to match. And only to the right of the colon.

• Hi. I'm Bob. I speak русский and this string should match




• Hi Bob. I speak 한국어 and this string should also match

I'm currently using (^[a-z0-9_]+(?=:)) to match characters to the left of :. I just can't seem to reverse the logic.

The closest I have at the moment is (?!(?!:)).+. This seems to match everything to right of the colon as well as the colon itself. I just can't figure out how to not include : in the match.

Can one of you regex wizards help me out? If anything is unclear please let me know.

Answer

Short regex pattern (case insensitive):

^\w+:(\w.*)

• \w - matches any word character (equal to [a-zA-Z0-9_])

https://regex101.com/r/MZhqSL/6

---

As you marked pcre, here's the pattern you need (only to the right of the colon):

^\w+:\K\w.*

• \K - resets the starting point of the reported match. Any previously consumed characters are no longer included in the final match

https://regex101.com/r/E1yHVY/1