for variable-name in list
do
    execute one iteration for each item in the
            list until the list is finished
done

sum=0
for i in 1 2 3 4
do
sum=$(($sum+$i))
done
echo $sum

while condition is true
do
    Commands for execution
    ----
done

echo "enter number"
read num
fact=1
i=1
while [ $i -le $num ]
do
        fact=$(($fact*$i))
        i=$(($i+1))
done
echo "Fact de $num is $fact"

until condition is false
do
    Commands for execution
    ----
done

echo "waiting..."
mn=1
mx=10
until [ $mn -gt $mx ]
do
        echo "$mn"
        mn=$(($mn+1))
done
echo "ready"