- exit 退出程序
- continue 进行下一次循环
- break 退出循环
- shift 输入参数位移
```
#! /bin/env bash

sum=0
for i
do
	let sum+=$i
done
echo $sum
```

```
#! /bin/env bash

sum=0
while [ $# -ne 0 ]
do
	let sum+=$1
	shift
done
echo $sum
```

```
#! /bin/env bash

sum=0
while [ $# -ne 0 ]
do
	let sum+=$1
	shift 2
done
echo $sum
```