Shell Programming and Scripting

#!/bin/bash
if [ $# -ne 3 ]; then
    echo "Illegal number of parameters"
    exit 1
fi

if [ $(who |grep -w "^$0" |wc -l) -eq 0 ]
 then
 echo User $1 is not connected
 exit
fi

if (-F $2) then 
    echo "Argument 2 is folder"
elif (-D $2) then 
    echo "Argument 2 is directory"
fi

if (-F $3) then 
    echo "Argument 3 is folder"
elif (-D $3) then 
    echo "Argument 3 is directory"
fi

mkdir backup

tar -cvf $1.tar backup/
tar -cvf $2.tar $3/
cp $3.tar $3/
cd $3
tar -xvf $2.tar
if [$3 type -f]
$2.tar >> $3
fi