+ 运算
count=0 let count=count+2 let count+=2 echo $count
- 运算
count=0 let count=count-2 let count-=2 echo $count
运算
count=1 let count=count*2 let count*=2 echo $count
/ 运算
count=8 let count=count/2 let count/=2 echo $count
取 余
count=33 let count=count%10 let count%=2 echo $count