rev - reverse lines
$ rev [files...]
rev
reads the specified files line by line, and prints them to standard output with each line being reversed characterwise. If no files are specified, then rev
will read from standard input.
To print two files 'foo' and 'bar' in reverse:
$ cat foo bar
foo 1
foo 2
bar 1
bar 2
$ rev foo bar
1 oof
2 oof
1 rab
2 rab
To list files with their names in reverse:
$ ls
foo
bar
$ ls | rev
oof
rab