tac - concatenate and print files in reverse tac [-br] [-s separator] [--before] [--regex] [--separator=separator] [--help] [--version] [file...] This manual page documents the GNU version of tac . tac copies each given file, or the standard input if none are given or when a file name of `-' is encountered, to the standard output with the order of the records reversed. The records are separated by instances of a string, or a newline if none is given. By default, the separator string is attached to the end of the record that it follows in the file.

"-b, --before" The separator is attached to the beginning of the record that it precedes in the file.

"-r, --regex" The separator is a regular expression.

"-s, --separator separator" Use separator as the record separator.

"--help" Print a usage message and exit with a non-zero status.

"--version" Print version information on standard output then exit.