bash 算術(shù)運(yùn)算

基本算術(shù)運(yùn)算符

• 加, -減, *乘, /除, **取模

bash中的let支持的算術(shù)運(yùn)算符

使用help let 查看bash的運(yùn)行符和表達(dá)式

    id++, id--  variable post-increment, post-decrement
    ++id, --id  variable pre-increment, pre-decrement
    -, +        unary minus, plus
    !, ~        logical and bitwise negation
    **      exponentiation
    *, /, %     multiplication, division, remainder
    +, -        addition, subtraction
    <<, >>      left and right bitwise shifts
    <=, >=, <, >    comparison
    ==, !=      equality, inequality
    &       bitwise AND
    ^       bitwise XOR
    |       bitwise OR
    &&      logical AND
    ||      logical OR
    expr ? expr : expr
            conditional operator
    =, *=, /=, %=,
    +=, -=, <<=, >>=,
    &=, ^=, |=  assignment

bash 算術(shù)運(yùn)算

(1) let var = 算術(shù)表達(dá)式 注意運(yùn)算項(xiàng)之間不能由空格
例如：let a=2+3
let b=$a+$b

(2) var = $[算術(shù)表達(dá)式]
例如： a=$[2+3]
b=$[$m+$n]
echo " this is the $[$x+$y] time"

(3) var=$(($x+$y))
例如: echo $((3+4))

(4) var=$(expr arg1 符號(hào) arg3...)
例如： echo $(expr 1 + 3)
echo $(expr 2 * 10) 算法符號(hào)需要轉(zhuǎn)義

bash隨機(jī)數(shù)生成器
BASH內(nèi)建的隨機(jī)數(shù)生成器 $RANDOM可以生成1-32767之間的隨機(jī)數(shù)