Linux查看并发连接数
指令
netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'
结果
[root@izbp10ebr6tsvo83iahgzdz ~]# netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'
CLOSE_WAIT 3
ESTABLISHED 87
FIN_WAIT2 9
TIME_WAIT 25
语句解析
命令的核心是awk指令简单的说就，用awk以 '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'规则去解析netstat -n的结果
第一步：netstat -n，结果如下
[root@izbp10ebr6tsvo83iahgzdz ~]# netstat -n Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 192.168.0.162:57616 100.100.30.25:80 ESTABLISHED tcp 0 0 192.168.0.162:6379 120.26.55.92:55830 ESTABLISHED tcp 0 0 192.168.0.162:55764 120.26.55.92:6379 ESTABLISHED tcp 0 0 192.168.0.162:48556 47.111.164.6:9092 ESTABLISHED tcp 0 0 192.168.0.162:55776 120.26.55.92:6379 ESTABLISHED tcp 0 0 192.168.0.162:50172 47.111.219.84:3306 ESTABLISHED tcp 0 0 192.168.0.162:55766 120.26.55.92:6379 ESTABLISHED tcp 0 0 192.168.0.162:443 101.247.3.249:41142 ESTABLISHED tcp 0 0 192.168.0.162:55792 120.26.55.92:6379 ESTABLISHED tcp 0 0 192.168.0.162:6379 120.26.55.92:55832 ESTABLISHED tcp 0 0 192.168.0.162:443 101.247.3.249:41082 FIN_WAIT2 tcp 0 0 192.168.0.162:27017 119.61.6.133:53930 ESTABLISHED tcp 0 0 192.168.0.162:34212 120.26.55.92:27017 ESTABLISHED tcp 0 0 192.168.0.162:55830 120.26.55.92:6379 ESTABLISHED tcp 0 0 192.168.0.162:443 49.98.141.94:23375 TIME_WAIT tcp 0 0 192.168.0.162:6379 120.26.55.92:55782 ESTABLISHED
这里特别留意下第一列Proto和最后一列state
第二步：awk的解析，规则是 '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}'，awk是逐行解析；
2-1- /^tcp/，正则匹配当前行数据是以tcp开头
2-2- $NF，是指当前行的最后一个字段，比如ESTABLISHED
2-3- S[$NF]，以$NF为index，建立数组S
2-4- {++S[$NF]} ，每当找到一个$NF，就在给数组(下标是$NF)的值加1；
2-5- END， 表示执行完'/^tcp/ {++S[$NF]} ，在执行后面指令
2-6- {for(a in S) print a, S[a]}，这是一个for循环语句，表示遍历数组S，同时打输出下标和值
2-7- awk '...' 解析并输出结果
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