$ cat swap.txt
a b
c d
e f
g h
i j
k l
$ awk ‘{print $2,$1}’ swap.txt
b a
d c
f e
h g
j i
l k

$ find . -empty -ls

536650 4 drwxr-xr-x 2 kamaraj kamaraj 4096 Aug 25 20:56 ./saa
540876 0 -rw-r–r– 1 kamaraj kamaraj 0 Jan 16 2011 ./9
520317 4 drwxr-xr-x 2 kamaraj kamaraj 4096 Apr 10 02:27 ./.abc
520314 0 -rw-r–r– 1 kamaraj kamaraj 0 Jul 31 16:41 ./empty.txt
536649 4 drwxr-xr-x 2 kamaraj kamaraj 4096 Aug 25 20:56 ./empty
521312 0 -rw-r–r– 1 kamaraj kamaraj 0 Jan 16 2011 ./9.5
540800 0 -rw-r–r– 1 kamaraj kamaraj 0 Jan 16 2011 ./core