syntax
$ tac [OPTION]... [FILE]...

$ cat example.txt
This is line 1
This is line 2
This is line 3
This is line 4
This is line 5

$ cat example1.txt

This is msg 1
This is msg 2
This is msg 3
This is msg 4
This is msg 5

To print files in reverse

$ tac example.txt 

To attach the separator before instead of after

$ tac -b example.txt example1.txt

To make the STRING as the separator

$ tac --separator="STRING" example1.txt example.txt

To interpret the separator as a regular expression

$ tac -r example.txt example1.txt

regards,

T.Dhanasekar