使用shell进行数学运算

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可以利用 let、(())、[]进行基本的算术操作，高级操作使用bc更加高效。

直接看代码把，输出很清楚。

let

[zhengweiwu 22:17 ~]$ no1=4[zhengweiwu 22:24 ~]$ no2=5[zhengweiwu 22:24 ~]$ let result=no1+no2[zhengweiwu 22:24 ~]$ echo $result9[zhengweiwu 22:24 ~]$ let result=result + 0.9 # 运算符两侧不能有空格-bash: let: +: syntax error: operand expected (error token is "+")[zhengweiwu 22:25 ~]$ let result=result+0.9 # 只能进行整数运算-bash: let: result=result+0.9: syntax error: invalid arithmetic operator (error token is ".9")[zhengweiwu 22:25 ~]$ echo $result9

[]

[zhengweiwu 22:26 ~]$ result=$[no1+no2][zhengweiwu 22:27 ~]$ echo $result9[zhengweiwu 22:27 ~]$ result=$[no1+no2+1][zhengweiwu 22:27 ~]$ echo $result10

(())

[zhengweiwu 22:28 ~]$ result=$((1+1))[zhengweiwu 22:28 ~]$ echo $result2[zhengweiwu 22:28 ~]$ result=$(( 10 +1))[zhengweiwu 22:29 ~]$ echo $result11

bc

[zhengweiwu 22:29 ~]$ echo "4*3.5" | bc14.0[zhengweiwu 22:29 ~]$ echo "4*3.54" | bc14.16[zhengweiwu 22:30 ~]$ result=$(echo "$no1*0.44" | bc)  # 作为子shell计算结果[zhengweiwu 22:30 ~]$ echo $result1.76

[zhengweiwu 22:30 ~]$ echo "scale=2;3/8" | bc # 设定小数精度.37[zhengweiwu 22:31 ~]$ echo "scale=4;3/8" | bc.3750[zhengweiwu 22:31 ~]$ echo "scale=6;3/8" | bc.375000

[zhengweiwu 22:31 ~]$ no=100[zhengweiwu 22:33 ~]$ echo "obase=2;$no" | bc # 输出为2进制，默认输入进制为10进制1100100[zhengweiwu 22:33 ~]$ no=1100100[zhengweiwu 22:33 ~]$ echo "obase=10;ibase=2;$no" | bc # 指明输出进制和输入进制100

[zhengweiwu 22:34 ~]$ echo "sqrt(100)" | bc10[zhengweiwu 22:35 ~]$ echo "10^10" | bc10000000000