I'm trying to create a regular expression to match a Markdown heading that correlates to a package version number, e.g.

## 5.21.30

Currently I'm using this regex:

^##\s([0-9] \.?[0-9] \.?[0-9] )

The problem is this is also returning the ##\s. I want to remove this, so I attempted to make it into a non-capturing group.

/(?:^##\s)([0-9] \.?[0-9] \.?[0-9] )/gsm

But this doesn't seem to work (same output as before).

Any help on what I'm misunderstanding would be appreciated.

CodePudding user response：

?: makes a non-capturing group, but it's still a group and part of the match. You could use a lookbehind:

(?<=^##\s)([0-9] \.?[0-9] \.?[0-9] )

e.g. https://regex101.com/r/3s0p7X/1

The ?<= means that part has to appear before the numbers, but is not a group and is not part of the match. See also lookarounds at regular-expressions.info.