awk计算

chris@ubuntu:~$ echo "3.2 2.2" | awk '{print $1+$2}'
5.4
chris@ubuntu:~$ echo "3.2 2.2" | awk '{print $1*$2}'
7.04
chris@ubuntu:~$ echo "3.2 2.2" | awk '{print $1+4*$2}'
12