Question

I am wanting to match files that have not already got thumbnails created.

So, for an image that has had two thumbnails created:

image1-100x100.png
image1-350x350.png
image1.png

I am looking for some regex to match only image1.png.

What I have at the moment selects the extensions only:

(?!(-(100x100|350x350)))(\.(jpg|png))

Answer 1

Try this:

^(?!.*-(?:100x100|350x350)).*\.(?:jpg|png)$

Explanation:

^                     # Start of string
(?!                   # Assert that it's impossible to match...
 .*                   # any string, followed by
 -                    # a dash, followed by
 (?:100x100|350x350)  # 100x100 or 350x350
)                     # End of lookahead.
.*                    # Then match any string
\.                    # followed by a dot
(?:jpg|png)           # and a jpg/png extension.
$                     # End of string