tcp-connection-state-counter

#!/bin/bash
# @Function
# show count of tcp connection stat.
#
# @Usage
#   $ ./tcp-connection-state-counter
#
# @online-doc https://github.com/oldratlee/useful-scripts/blob/dev-2.x/docs/shell.md#-tcp-connection-state-counter
# @author Jerry Lee (oldratlee at gmail dot com)
# @author @sunuslee (sunuslee at gmail dot com)
set -eEuo pipefail

# On MacOS, netstat need to using -p tcp to get only tcp output.
uname | grep Darwin -q && option_for_mac="-ptcp"

netstat -tna ${option_for_mac:-} | awk 'NR > 2 {
    ++s[$NF]
}

END {
    # get max length of stat and count
    for(v in s) {
        stat_len = length(v)
        if(stat_len > max_stat_len) max_stat_len = stat_len

        count_len = length(s[v])
        if (count_len > max_count_len) max_count_len = count_len
    }

    for(v in s) {
        printf "%-" max_stat_len "s %" max_count_len "s\n", v, s[v]
    }
}' | sort -nr -k2,2