UNIX Command $ls a1.txt a2.txt $ls . ./ ../ $cp a1.txt a1.txt~ $ls a1.txt a1.txt~ a2.txt $ls -B a1.txt a2.txt $l bash: l: command not found $ls a1.txt a1.txt~ a2.txt $ls –backup ls: unrecognized option ‘–backup’ Try `ls –help’ for more information. $ls –ignore-backups a1.txt a2.txt $