Find all missing entries in two files

I have two csv-Files containing 30k customer information and should only return the customers missing in file1. Usecase: accidentially deleted some data (~1800) and need to import the deleted one, instead of importing 30k data and skip if they exist.

I did this via a small shell-script. The script can be downloaded and used here:

View Gist on Github

This is the magic

grep -v -f <(tr ',' '\n' < "${patterns}") "${search}"

-v negates the search