Multiple ways to perform mathematical operations through the shell _linux shell

In bash, Bash's math is a little awkward, it's hard to adapt and remember, so you have to write a blog post to make it easier to look through. There are four ways to perform mathematical operations:

A, let order

Copy Code code as follows:

#/bin/bash
Num1=13
Num2=14
Let sum= $num 1+ $num 2

Echo $sum

#自增
Let sum++

#自减
Let sum--

#简写形式
Let Sum+=1
Let sum-=2

#顺便吐槽下, let sum= (1+3) * (2+2) Incredibly not, really rotten there!

II, $[] form

Copy Code code as follows:

#!/bin/bash
sum = $[99+88]

#[] also uses variables
num1=11
Num2=22
sum=$[$num 1+ $num 2]

Three, $ (()) way

Copy Code code as follows:

#!/bin/bash
sum=$ ((1+2))

# $ (()) can be used () for priority operation arrangement
Sum=$ (((1+2) *3))
Echo $sum #9

Iv. You can also use the expr command, which requires an operand and an operation symbol to be empty

Copy Code code as follows:

#!/bin/bash
Expr 3 + 4 #7

sum= ' expr ' #33后有空格, "+" after a space, if the writing is sum= ' expr 3+4 ', echo $sum will be 33+44
Echo $sum #77

The above 4 kinds of methods do not support floating-point operations, to carry out floating-point operations, you should use the BC command, syntax format is relatively simple:

Copy Code code as follows:

#!/bin/bash

Sum= ' echo 222.222+333.333 | BC '
Echo $sum

#sum = ' echo 12.228222+ (22222*2) | BC ' incredibly not, decisively despise it.