算术运算
(1)bash 中的算术运算:
help let +, -, *, /, % 取模(取余), ** (乘方)
(2)实现算术运算:
- (1) let var= 算术表达式
- (2) var=$[ 算术表达式]
- (3) var=$(( 算术表达式))
- (4) var=$(expr arg1 arg2 arg3 …)
- (5) declare –i var = 数值
- (6) echo ‘ 算术表达式’ | bc
- (7) 乘法符号有的场景需要转义
*
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| [root@localhost ~]# num1=1 [root@localhost ~]# num2=2 [root@localhost ~]# let sum=${num1}+${num2} && echo $sum 3 [root@localhost ~]# echo $[${num1}+${num2}] 3 [root@localhost ~]# echo $((${num1}+${num2})) 3 [root@localhost ~]# mult=$(expr ${num1} \* ${num2}) [root@localhost ~]# echo $mult 2 [root@localhost ~]# declare -i var=${num1}+${num2} && echo $sum 3 [root@localhost ~]# echo "${num1}+${num2}" | bc 3
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(3)增强型赋值:+=, -=, *=, /=, %=
let var OPER value
例如:
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| 自增,自减: let var+=1 let var++ let var-- [root@localhost ~]# var=0 [root@localhost ~]# let var+=1 && echo $var 1 [root@localhost ~]# let var++ && echo $var 2 [root@localhost ~]# let var-- && echo $var 1
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