Regex for filenames without using lookbehind

Question

I'm trying to match all files which don't end in jpg/png/jpeg/gif, and which also do not have a filename starting with a ..

I'm passing this regex into find like so:

find -E path/to/dir myregex

Here's the regex

^.*\/[^\.].*\.(?!jpeg$)(?!jpg$)(?!gif$)(?!png$)([^jgp]..|j[^p].|g[^i].|p[^n].|jp[^g]|gi[^f]|pn[^g]|jpg.+|png.+|gif.+|jpe[^g]|jpeg.+)[^\.]*$

It does appear to work, but man is it long... One possibility would be to write a function to generate it... but I wish there was an easier way.

I don't think the version of find that I'm using (OS X Mavericks) supports lookbehind, but even if it did, I'd like to know if there was an alternative.

Here's an interactive version: http://regex101.com/r/xD9qC2/1

Answer 1

Sorry for the self Q&A here. I spent a while thinking about this before posting my question, but just after posting I had some insight.

It's a little long but it's less brute-forced than the one in the question.

(?:^.{1,3}$)|(?:^(?!\.(?:jpg|gif|png)$).{4}$)|(?:^.*(?!.*\.(?:jpg|gif|png|jpeg)$).{5}$)

Interactive link