bc是unix/linux下的计算器，因此 除了可以作为计算器来使用 还可以作为命令行计算工具使用
[root@server1 mnt]# bc
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
1.1+1.2
2.3
[root@VM_0_15_centos ~]# echo 3+5|bc
8
[root@VM_0_15_centos ~]# echo 3.3+5.3|bc
8.6
[root@VM_0_15_centos ~]# echo 9.9-5.3|bc
4.6
[root@VM_0_15_centos ~]# echo 9-50|bc
-41
[root@VM_0_15_centos ~]# echo "scale=2;355/113"|bc #保留两位小数
3.14
[root@VM_0_15_centos ~]# echo "scale=6;355/113"|bc
3.141592
配合变量使用
[root@VM_0_15_centos ~]# i=5
[root@VM_0_15_centos ~]# i=`echo $i+6|bc`
[root@VM_0_15_centos ~]# echo $i
11
$[]符号的运算式例子
[root@VM_0_15_centos ~]# i=5
[root@VM_0_15_centos ~]# i=$[i+6]
[root@VM_0_15_centos ~]# echo $i
11
[root@VM_0_15_centos ~]# echo $[2*3]
6
[root@VM_0_15_centos ~]# echo $[2**3]
8
[root@VM_0_15_centos ~]# echo $[3/5]
0
[root@VM_0_15_centos ~]# echo $[3/2]
1
[root@VM_0_15_centos ~]# echo $[3%2]
1
[root@VM_0_15_centos ~]# echo $[3%5]
3
[root@VM_0_15_centos ~]# echo $[ 3 % 5 ]
3
[root@VM_0_15_centos ~]# echo $[ 3 / 5 ]
0