shell运算

[root@bogon ~]# cat a.sh
#!/bin/bash
a=6
b=2
echo "a-b =$(( $a - $b ))"
echo "a+b =$(( $a + $b ))"
echo "a*b =$(( $a * $b ))"
echo "a/b =$(( $a / $b ))"
echo "a**b =$(( $a ** $b ))"
echo "a%b =$(( $a % $b ))"

结果：
[root@bogon ~]# sh a.sh
a-b =4
a+b =8
a*b =12
a/b =3
a**b =36
a%b =0
[root@bogon ~]# 

[root@bogon ~]# cat a.sh 
#!/bin/bash
echo $(($1$2$3))
[root@bogon ~]# sh a.sh 1+1
2
[root@bogon ~]# sh a.sh 1**1
1
[root@bogon ~]# sh a.sh 1/1 
1
[root@bogon ~]#