ls should not be displaying the total line twice like that. I do not believe that you are using a standard version of ls. Repeat your experiment, but whereever you would type "ls", instead type "/usr/bin/ls".

Also what shell are you using? What do you get when type "whence ls"? Also "which ls"?

On SunOS 5.8, when I type "cksum /usr/bin/ls" I get "169775630 18844 /usr/bin/ls". What do you get?