Seems to be related to $, as removing it does give the shortest match: https://play.golang.org/p/zCRKd3vO2k

However, that matches the first c, not the second - that's not what I want. It looks like $ messes up the non-greedy *?, making the regex end with a match too early.

To give a bit of context, I was trying to use the regexp package to implement Bash pattern matching, in particular for prefix/suffix stripping:

$ x=aabcc; echo ${x%c*} # % means shortest suffix
aabc
$ x=aabcc; echo ${x%%c*} # %% means longest suffix
aab

FindString is documented to return the leftmost match. cc is indeed the leftmost match of c.*?$ on aabbcc, and it is also the shortest match at that location because of the $.

You're absolutely right, I missed that entirely. I'm still wondering if this is at all possible, but at least it's not a bug in the regexp package.

This is a little hacky, but I think you can get what you want by reversing the regexp and the string.

https://play.golang.org/p/a2qrgP2nQa

Thanks for the tip - something similar had occurred to me, but I was thinking there had to be a simpler way.

Perhaps using a leading .* and capturing a submatch? Seems to work, not sure if it's exactly what I'm after though. https://play.golang.org/p/woWJC5ZOC8

Also, I realise that the .*(expr) approach may do more work than the reversing approach, but the strings involved here are all short. So I'm prioritizing simplicity over performance.