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
