operator of the Shell

an arithmetic operator:

+-*/% (take more) * * (Power) 1.1 expr evaluates an expression value

Expr expression (expr cannot calculate a power operation)

Example:

#。 /bin/bash

#计算2和100的差, i.e.-98

result= ' Expr 2-100 '

echo "$result"

#计算2和100的和, which is 102

result= ' Expr 2 +100 '

echo "$result"

#计算2和5的乘积, which is 10

result= ' Expr 2 \*5 '

echo "$result"

#计算24和8的商, which is 3

result= ' Expr 24/8 '

echo "$result"

#先计算2和6的差, then multiply by 12, i.e.-48

result= ' expr \ (2-6 \) \* 12 '

echo "$result"

#错误的语法, no spaces

result= ' Expr 2+5 '

echo "$result"

#错误的语法

result= ' expr2-4*9 '

echo "$result"

#错误的语法

Result= ' expr1-(4-7) '

echo "$result" 1.2 is calculated with $ (()) :

#! /bin/sh

#紧凑格式, calculates the and of 3 and 6

result=$ ((3+6))

echo "$result"

#松散格式, calculates the and of 3 and 9

Result=$ ((3 + 9))

echo "$result"

#计算3和6的乘积

reuslt=$ ((3 * 6))

echo "$result"

#计算7和5的商

result=$ ((7/5))

echo "$result"

#计算8和3的余数

result=$ ((8% 3))

echo "$result"

#复合运算

Result=$ (((1-4) * 5))

echo "$result"

1.3 calculated using $[]

#! /bin/sh

#加法运算

RESULT=$[4+5]

echo "$result"

#复合运算

result=$[(1+2)

echo "$result"

#幂运算

result=$[2 * * 4]

echo "$result"

1.4 calculation with let command

The Let command executes one or more arithmetic expressions, and the variable name does not need to be $, and if the expression has spaces or other special characters, it is referenced.

#! /bin/sh

#定义变量

n=10

#加法运算

Let N=n+1

echo "$n"

#乘法运算

Let n=n*10

echo "$n"

#幂运算

Let N=n**2

echo "$n" two-bit operator

<< left Shift

>> Right Shift

& Bitwise AND

| Bit or

~ Bit non-

^ bit XOR or 2.1 self-increment decrement operator:

++varibale first add 1, and then assign to variable

--variable first minus 1, then to variable.

vaiable++ first with variable, plus 1.

variable--first with variable, and then minus 1 2.2 numeric constants in the system:

By default, the shell represents a number in decimal, and it can be binary, octal, and hexadecimal.

Added prefix: 0 means 8 hexadecimal, 0x

The well number #:2#100 represents 2 binary, and 8#42 represents 8 binary