Regular expression to match optional numeric string

I'm trying to build a regular expression to match a string somthing like

Sample:

3232asdfADFF/ew323fdffADF 4243dsafAFDF 232 (total 42)
<----p1---->/<---p2-----> <----p3----> P4            

I could successfully match till p3 but unab开发者_JS百科le to match last part i.e. p4 The p4 is essentially numeric string, having length 0 to 3 (abscent or max 3).

I'm using:

[0-9A-Za-z]{2,12}/[0-9A-Za-z]{3,12} [0-9A-Za-z]{0,12}\\b \\d{0,3}$

But the problem I'm facing is that it fails if I completely remove p4 from input. And succeeds with even if on number.

This should work for you, I think:

[0-9A-Za-z]{2,12}/[0-9A-Za-z]{3,12}(?: [0-9A-Za-z]{1,12})?(?: \\d{1,3})?$

Of course it fails if you have no space. You should have something like ( \d{0,3})?$ I think.

As I mentioned in a comment, not sure what may/may not exist in the pattern. But, best guess effort, here's what I've come up with:

\w{3,12}\/\w{3,12} (?:\w{0,12} )?\d{0,3}

That will match everything up until the (total 42). If you need to include that as well, you can add:

(?: \(\w+ \d+\))?

To the end of the pattern. Again, best effort based on what I see and what I'm guessing should be the result. If it's not what you're going for, leave me a comment and I can adjust it.

(Also, for the sake of length I replaced the [0-9a-zA-Z] with \w. Though it's not a direct one-to-one replacement, it was close. If you need it to be explicitly the previous pattern, replace the \w back to your original class.)