```
filename=""
while [[ $filename = "" ]];do
    echo "Enter the file name"
    read filename
    if [[ -f $filename ]];then
        echo "$filename exists"
    else
        echo "File name doesn't exists, so re-enter"
    fi
done

```

with this style of loop, the loop exists when the file name is not present.
But i want the loop to continue until the user input the file name.
Please suggest what additional command i should include in the above script.