Regex C++: extract substring

Question

I would like to extract a substring between two others.
ex: /home/toto/FILE_mysymbol_EVENT.DAT
or just FILE_othersymbol_EVENT.DAT
And I

Answer 1

TRegexp only supports a very limited subset of regular expressions compared to other regex flavors. This makes constructing a single regex that suits your needs somewhat awkward.

One possible solution:

[^_]*_([^_]*)_

will match the string until the first underscore, then capture all characters until the next underscore. The relevant result of the match is then found in group number 1.

But in your case, why use a regex at all? Just find the first and second occurrence of your delimiter _ in the string and extract the characters between those positions.