[BASH]Until, For, While Loop计算1到100的和

While Loop

#!/bin/bash
var=1
total=0
while [ $var -lt 101 ]; do
    total=$((total + var))
    var=$((var+1))
done
echo sum is $total

 

注意：

1.“=”两边一定不能有空格

2.

上面的

total=$((total + var))
var=$((var+1))

可以换成：

total=`expr $total + $var`
var=`expr $var + 1`

下面的循环同理

 

Until Loop

#!/bin/bash
var=1
total=0
until [ $var -gt 100 ]; do
    total=$((total + var))
    var=$((var+1))
done
echo sum is $total

 

 

For Loop

#!/bin/bash
total=0
for var in `seq 1 100`; do
    total=$((total + var))
done
echo sum is $total