Powershell script to delete files not specified in a list

Question

I have a list of filenames in a text file like this:

f1.txt
f2
f3.jpg

How do I delete everything else from a folder except these files in P

Answer 1

If the files exist in the current folder then you can do this:

Get-ChildItem -exclude (gc exclusions.txt) | Remove-Item -whatif

This approach assumes each file is on a separate line. If the files exist in subfolders then I would go with Oisin's approach.