TAC(1) General Commands Manual TAC(1)

concatenate reversed files

tac [-rb] [-s eparator] [file]…

Read each file (or standard input if “-”), split it on the separator expression, matching from the end, and print it back out, starting with the final match. file defaults to “-”.

, --separator=sep
Separate with sep instead of a single newline. An empty separator matches nothing (and the invocation is equivalent to cat).
, --regex
Treat separator as regular expression. An empty separator is refused.
, --before
Print separator before its line.
June 7, 2021 voreutils 8252842