为什么bash中的$((sum + = i))告诉我"命令未找到"？

Question

目标是有一个bash脚本,它将从1到N的整数相加,其中N由用户定义.这是我的代码:

#!/bin/bash

read -p "Enter an integer greater than zero: " N  #allows the user to enter a value, which is then read from stdin and assigned to N

sum=0

for ((i=0; i<=N; i++))

do

  $((sum+=i))  #add i to sum each iteration

done

echo "The sum of the numbers from 1 to $N is $sum"

输出:

Enter an integer greater than zero: 5
-bash: 0: command not found
-bash: 1: command not found
-bash: 3: command not found
-bash: 6: command not found
-bash: 10: command not found
-bash: 15: command not found
The sum of the numbers from 1 to 5 is 15

求和是正确的.我意识到每次迭代的总和导致某种错误(b/c 0,1,3,6 ...是每个i的求和值),但我不确定为什么或如何修理它.有没有办法在vi中调试？谢谢

Answer 1

降$在面前:

((sum+=i))

$(()) 将进行算术扩展,并将扩展的结果视为运行导致错误消息的命令.