tac [OPTION]... [FILE]...
Write each FILE to standard output, last line first. With no FILE, or
when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options
too.
-b, --before
attach the separator before instead of after
-r, --regex
interpret the separator as a regular expression
-s, --separator=STRING
use STRING as the separator instead of newline
--help display this help and exit
--version
output version information and exit