if [ $# -le 0 ]; then
    echo "usage: $0 <DIR> [ DIR ... ]"
    exit 1
fi

for dir in $@; do
    echo -n "ext: "
        read ext
        while [ ! $ext = "END" ]; do
            nfiles=$(ls -l $dir/*.$ext 2>/dev/null|wc -l)     #   2>dev/null    redireziona i messaggi di errore in /dev/null (in pratica non li visualizza)
            if [ $nfiles -eq 0 ]; then
                echo "no $dir/*.$ext files to remove"
            else
                rm -f $dir/*.$ext
                echo "removed $nfiles $dir/*.$ext files"
            fi
            echo -n "ext: "
            read ext
    done
done