How to grep this and NOT that?

Question

I am trying to return a file name from list.files, but there are 2 similarly named files. filename.csv filename_review.csv

I want to put each file name into its own list. Doing that for filename_review.csv is easy since it has unique stuff in it, but how do I sift out the other? I need to grep(".csv", list.files()) without getting filename_review.csv returned.

Answer 1

Showing all files in the working directory that has a csv extension but not ends in review could be done:

setdiff(list.files(pattern='.csv$'), list.files(pattern='review.csv$'))