日期循環bash腳本

start_date=20190907
end_date=20190918


for((i=$start_date;$i<$end_date;));do
    j=$i;
    i=`date -d"$j +1 days" +"%Y%m%d"`;
    echo $i;

    #do sth to file $i
    if [ ! -f "$i" ]; then
        echo " do sth. to ${i}"
    fi  
                               
                           
done