shell中while循环的常用写法

写法一：

#!/bin/sh
int=1
while (( "$int < 10" ))
do
    echo "$int"
    let "int++"
done

写法二：

#!/bin/sh
echo "please input the num"
read num
sum=1
while [ "$num" -gt 0 ]
do
    let "sum=sum*num"
    let "num--"
done
echo "the sum is $sum"