https://www.runoob.com/linux/linux-comm-awk.html
https://www.cnblogs.com/zhoujishan/p/13509527.html#auto-id-10
https://www.cnblogs.com/A121/p/10621213.html
登录失败的IP计数
lastb|awk '{x[$3]++;} END{for(i in x) print(i ":" x[i])}'