awk 按多個字符進行切割

[root@xiaoyuan ~]# ip a s eth0 | grep inet
　　inet 172.31.142.158/20 brd 172.31.143.255 scope global dynamic eth0

　　inet 192.168.170.133/24 brd 192.168.170.255 scope global eth0:1
[root@xiaoyuan ~]# ip a s eth0 | grep inet | awk -F '/|[ ]' 'NR==1{print $6}'
172.31.142.158

注意：inet前面有4個空格，切割后$1~$4都是空字符串。