let n=99999999
for ((i=1;i<=n;++i)) 
do 
if (($i < 10)); 
then 
l=$(expr length "$n" - 1)
result=$( printf "%${l}s" );
else 
s=$(expr length "$i") 
l=$(expr length "$n" - ${s}) 
fi 
echo "${result// /0}"$i >> "numbers.txt" 
done