TAB button doesn't work properly

Linux and Unix-Like Red Hat
1

Hi,

I have list of files under a directory as shown below.

/home/root 
-rw-r--r-- 1 user 0 Aug 27 06:08 rough.txt
-rw-r--r-- 1 user 0 Aug 27 06:08 test.sh

Now when i use to read the rough.txt, i did cat r and then pressed TAB button. Below is the resulting string after pressing TAB button,

$ cd rough.txt o
$ cd test.sh e

What am i doing wrong here?

2

What shell are you using?

3

It is Korn shell..