shell脚本计算两个整数之间所有整数的和

使用for循环：

#!/bin/sh
#a:the start num  b:the end num
#Calculates the sum of all integers between two Numbers
#a<b
read -p 'please input the starting num:' a
read -p 'please input the end num:' b
for i in `seq $a $b`
do
        sum=$[$sum+$i];
done
echo $sum