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 filename 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 string, –separator=string||Use string 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.|