Reverse chronological order, mostly

tac log.txt |head # would give you newest first

no good for sort because sort already supports -r

no need it for tail on large files because tail already skips to the end.

I do a lot of impromptu bash to sus crap out of logs.

when you're balls deep in

cat log|grep -v foo| rev|cut -f 1-3 -d \ | |rev

Sometimes tac comes in clutch.