netstat -an|awk -F "[ :]+" '/ESTAB/ {S[$(NF-3)]++}END{for(k in S) print S[k],k}'|sort -rn|head 62 10.19.168.8615 180.168.234.2310 10.10.78.1656 10.9.145.1442 10.9.119.2531 127.0.0.11 10.9.190.181 106.75.53.121 10.19.60.1281 10.19.161.231-F [ :] 表示指定分隔符可以是：或者空格，这里指定多个分隔符
[ ]表示一个字符的集合，+则是一个正则表达式，表示+前面的字符(:或者空格)重复一次或者一次以上
例如：
[root@SRV-OPS10-ANSIBLE06 ~]# echo "1::::2 3 4" | awk -F '[: ]' '{print $4}'[root@SRV-OPS10-ANSIBLE06 ~]# echo "1::::2 3 4" | awk -F '[: ]+' '{print $4}'4第一个没有+号，查询结果为空，而有+后，查询结果为4
再例如：
# echo "1::::2 3 4" | awk -F ':' '{print $5}'2 3 4[root@SRV-OPS10-ANSIBLE06 ~]# echo "1::::2 3 4" | awk -F '[: ]' '{print $5}' 2以：作为分隔符，2 3 4被当做一个整体作为查询结果输出，而把空格加上后，则输出结果为2
netstat -an|awk -F "[ :]+" '/ESTAB/' tcp 0 0 10.9.154.150:58635 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:41777 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58815 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:38505 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:34508 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58692 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58812 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:32984 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:56873 10.9.190.18:10050 ESTABLISHED tcp 0 0 10.9.154.150:38997 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:42994 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58065 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58648 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:33109 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58641 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:22 180.168.129.46:54271 ESTABLISHED tcp 0 0 10.9.154.150:55594 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:33821 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:38948 10.19.132.153:10050 ESTABLISHED tcp 0 0 10.9.154.150:58695 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:39886 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:34063 10.10.78.165:10050 ESTABLISHED tcp 0 0 10.9.154.150:56932 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:38142 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58638 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58443 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58684 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:33678 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:33468 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58814 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58649 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58619 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58698 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58623 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58647 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:38518 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:60075 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:60963 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58611 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58813 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:37667 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:22 180.168.129.46:4449 ESTABLISHED tcp 0 0 10.9.154.150:42697 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:41785 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:2049 10.19.161.168:933 ESTABLISHED tcp 0 448 10.9.154.150:22 180.168.129.46:59852 ESTABLISHED tcp 0 0 10.9.154.150:45292 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58642 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58702 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58624 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58636 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58817 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:56991 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:56142 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:35332 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:39675 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:48701 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58816 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:33910 10.19.161.231:10050 ESTABLISHED tcp 0 0 10.9.154.150:58615 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:55459 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:854 10.19.140.120:2049 ESTABLISHED tcp 0 0 10.9.154.150:43902 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58811 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:59672 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58618 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58640 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58808 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:49803 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58639 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:60326 10.10.134.7:10050 ESTABLISHED tcp 0 0 10.9.154.150:55615 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:58637 10.19.168.86:3306 ESTABLISHED tcp 0 0 10.9.154.150:34295 10.10.78.165:10050 ESTABLISHED tcp 0 0 10.9.154.150:22 180.168.129.46:63288 ESTABLISHED
第一个ip是本机ip，第二个ip才是跟本机建立连接的外部ip，所以最上面的命令使用$NF-3来获取外部ip地址。
如果要改成以端口来查看连接数，可以将$NF-3改成$NF-2
# netstat -an | awk -F "[ :]+" '/ESTAB/ {S[$(NF-2)]++}END{for(k in S) print S[k],k}' |sort -rn|head 63 33068 100501 9331 80881 632881 607321 542711 458031 44491 443使用netstat命令统计established状态的连接数
原文地址：http://blog.51cto.com/zengestudy/2125549