shell scripts的算术运算

i=9

a=`expr $i + 1`
b=`expr $i - 1`
c=`expr $i / 3`
d=`expr $i /* 2`

echo "i+1 = $a "
echo "i-1 = $b "
echo "i/3 = $c "
echo "i/*2 = $d "

i=$(($i+1)) ##$((a+b)) means Integer computing(means 整形运算)
echo Integer i = $i

###记住$(( ))的用途，就是作为整数运算的
###我一般用let内置命令，因为很多系统最小安装后不会有expr
###可以let i=$i+1试试

let i=$i+1 ## same as the above
echo let i = $i

###要区分单引号和双引号.
i=1
echo $i
echo "$i"
echo '$i'
echo /$i

################ 以上运行输出
[ol@int8 tmp]$ ./computing.sh
i+1 = 10
i-1 = 8
i/3 = 3
i/*2 = 18
Integer i = 10
let i = 11
1
1
$i
/1