shell编程for循环的问题

Question

在linux下，应该怎样编程利用for循环实现1+2+..+n？

Answer 1

 #!/bin/bash
total=0
n=100
for ((j=1;j<=n;j++))
 do
  total=`expr $total + $j`
 done
 echo "The result is $total"

Answer 2

 int sum = 0;
 for ( int i = 1; i <= n; i++)
            sum = sum + i;

Answer 3

#! /bin/bash
total=0;
n=100
for((i=1;i<=n;i++))
do
let "total+=i"
done
echo $total