一 expr数值运算工具
aa=11
bb=22
dd=$(expr $aa + $bb)
echo $dd
注意 + 左右两边都有空格
二 实战
[[email protected] ~]# aa=11
[[email protected] ~]# bb=22
[[email protected] ~]# dd=$(expr $aa + $bb)
[[email protected] ~]# echo $dd
33
三 “$((运算式))”或“$[运算式]”
aa=11
bb=22
ff=$(($aa+$bb))
gg=$[$aa+$bb]
四 运算符
1、运算符
2、举例
五 实战
[[email protected] ~]# aa=11
[[email protected] ~]# bb=22
[[email protected] ~]# ff=$(($aa+$bb))
[[email protected] ~]# gg=$[$aa+$bb]
[[email protected] ~]# echo $ff
33
[[email protected] ~]# echo $gg
33
[[email protected] ~]# yy=$((4+9*3/5))
[[email protected] ~]# echo $yy
9
[[email protected] ~]# yy=$(((4+9)*3/5))
[[email protected] ~]# echo $yy
7
[[email protected] ~]# yy=$(((4+9)*3%5))
[[email protected] ~]# echo $yy
4
[[email protected] ~]# cc=$((1&&0))
[[email protected] ~]# echo $cc
0
[[email protected] ~]# cc=$((1&&1))
[[email protected] ~]# echo $cc
1
[[email protected] ~]# cc=$((1||1))
[[email protected] ~]# echo $cc
1