变量的运算
方法一:expr
(直接命令行操作即可) ##加减乘除
[root@localhost ~]# num1=10 [root@localhost ~]# num2=16 [root@localhost ~]# expr $num1 + num2 25 [root@localhost ~]# expr $num2 - num1 6 [root@localhost ~]# expr $num1 \* num2 160 [root@localhost ~]# expr $num2 \ num1 #默认不显示小数,取整 1
方法二:$(())
$符号加(())
[root@localhost ~]# num1=10 [root@localhost ~]# num2=16 [root@localhost ~]# echo $(($num1+$num2)) #加 26 [root@localhost ~]# echo $(($num1-$num2)) #减 -6 [root@localhost ~]# echo $(($num1*$num2)) #乘 160 [root@localhost ~]# echo $(($num2/$num1)) #除,默认取整数,不显示小数 1
方法三:$[]
$符号加[]
[root@localhost ~]# num1=10 [root@localhost ~]# num2=16 [root@localhost ~]# echo $[num1 + num2] #加 26 [root@localhost ~]# echo $[num1 - num2] #减 -6 [root@localhost ~]# echo $[num1 * num2] #乘 160 [root@localhost ~]# echo $[num2 / num1] #除,同上 1
方法四:let
let不直接输出
[root@localhost ~]# num1=10 [root@localhost ~]# num2=16 [root@localhost ~]# let sum=$num1+$num2;echo $sum #加 26 [root@localhost ~]# let sum=$num1-$num2;echo $sum #减 -6 [root@localhost ~]# let sum=$num1*$num2;echo $sum #乘 160 [root@localhost ~]# let sum=$num2/$num1;echo $sum #除 1
扩展:小数运算bc
scale=n;定义小数精度,此外可以直接运行bc命令进行输入计算
[root@localhost ~]# num1=1.8 [root@localhost ~]# num2=2.2 [root@localhost ~]# echo "scale=3;$num1+$num2" | bc 4.0 [root@localhost ~]# echo "scale=2;$num2-$num1" | bc .4 [root@localhost ~]# echo "scale=2;$num2/$num1" | bc 1.22 [root@localhost ~]# echo "scale=2;$num2*$num1" | bc 3.96
扩展:小数运算awk
awk -v 带入外部变量,'{ print num1 + num2 }'即可
[root@localhost project]# num1=2.1 [root@localhost project]# num2=1.5 [root@localhost project]# echo | awk -v num1=$num1 -v num2=$num2 "{print num1 + num2 }" 3.6 [root@localhost project]# echo | awk -v num1=$num1 -v num2=$num2 "{print num1 - num2 }" 0.6 [root@localhost project]# echo | awk -v num1=$num1 -v num2=$num2 "{print num1 * num2 }" 3.15 [root@localhost project]# echo | awk -v num1=$num1 -v num2=$num2 "{print num1 / num2 }" 1.4