shell之数值计算

1、shell 数字计算有4中方式

[oracle@rhel6 zxx_shell]$ cat 4-jisuan.sh 

#!/bin/bash

num1=520

num2=100

val1=$[$num1 + $num2 ]   #第一种：$[]

val2=$[$num1 - $num2 ]

val3=$[$num1 * $num2 ]

val4=$[$num1 / $num2 ]

val5=$[$num1 % $num2 ]

echo "val1=$val1"

echo "val2=$val2"

echo "val3=$val3"

echo "val4=$val4"

echo "val5=$val5"

a1=`expr $num1 + $num2`   第三种：` expr `

echo "a1=$a1"

a2=$(($num1 - $num2))   # 第二种：$(())

echo "a2=$a2"

let a3=$num1+$num2   #第四中：let  这种方式符号和数字必须紧贴在一起

echo "a3=$a3"

let a4=3**3      

echo "a4=$a4"

[oracle@rhel6 zxx_shell]$ ./4-jisuan.sh 

val1=620

val2=420

val3=52000

val4=5

val5=20

a1=620

a2=420

a3=620

a4=27