Extract content after colon if only one : exists in string

Question

I want to extract the content after the :, but there can be only one :.

Examples:

foo:bar             # match, extract 'bar'
foo:123             # match, extract '123'

foo:bar:123         # do not match

So that last example should not match because it has multiple :.

I tried a negative lookbehind ^.+(? but that nonetheless matches and extracts from that last example.


Here's a demo.

Andrej Kesely · Answer

Try (regex101):

^[^:]+:([^:]+)$

This will match only lines with one : and get the string after the :

The fourth bird · Answer

In C# you could also make use of lookbehind with an infinite quantifier to get a match only:

(?<=^[^:]*:)[^:]+$

Explanation

(?<= Positive lookbehind, assert what is to the left is
- ^ Assert the start of the string
- [^:]*: Match optional chars other than : followed by matching the :
) Close the lookbehind
[^:]+ Match 1+ chars other than :
$ End of string

If you don't want to cross newlines:

(?<=^[^:
]*:)[^:
]+$