Output whole line once for each unique value of a column (Bash)

Question

This must surely be a trivial task with awk or otherwise, but it\'s left me scratching my head this morning. I have a file with a format similar to this:

<

Answer 1

One way using awk:

awk '!array[$2]++' file.txt

Results:

pep> AEYTCVAETK     2   genes ADUm.1024,ADUm.5198,ADUm.750
pep> AIQLTGK        1   genes ADUm.1999,ADUm.3560
pep> KHEPPTEVDIEGR  5   genes ADUm.367
pep> VSSILEDKTT     9   genes ADUm.1192,ADUm.2731
pep> VSSILEDKILSR   3   genes ADUm.2146,ADUm.5750