Shell Programming and Scripting

i=0
while [ $i -le 999 ]
do
if [ $i le 9 ]
then
echo "00"$i
else if [ $i -gt 9 ] && [ $i -le 99 ]
then
echo "0"$i
else
echo $i
fi
i=`expr $i + 1`
done

for i in `seq 0 999`; do printf "%03d\n" $i; done

perl -e 'printf "%03d\n", $_  for (0..999);'

$ ruby -e 'print ("000".."999").to_a.join(" ")'

for i in {0..999} 
do
    printf "%03d\n" $i
done

printf "%03d\n" {0..999}