Ruby network interface information parser

nwinfo.rb

#!/usr/bin/env ruby

require 'json'

ifaces = []
whitelist = [ "eth", "wlan", "en" ]

names = `ip link sh`.scan(/^\d+: (.*):/).flatten.select do |name|
  whitelist.any? {|pattern| name.start_with?(pattern) }
end

names.each do |name|
  iface = {
    interface: name,
    ip: nil,
    gateway: nil,
    routed: false,
    enabled: false
  }

  # get the ip address out
  ip = `ip addr sh #{name} 2>/dev/null`
  next unless $?.success?
  addrs = ip.lines.grep(/inet /) # we are looking for a line like this:      inet 10.0.60.91/32 scope global enp6s0
  next if addrs.empty?
  iface[:ip] = addrs.first.split(" ")[1]

  # get the route
  routes = `ip route`.lines.grep(/#{name}/)
  if routes.first.start_with?("default")
    iface[:gateway] = routes.first.split(" ")[2]  # first line always has default: default via 192.168.1.1 dev eth0  metric 1024
    iface[:routed] = true  # if this interface is on the first line, all traffic is routed through it
  else
    iface[:routed] = false
    routes.each do |r|
      next if r.include?("proto kernel") # ones with this line seem to be network routes:                  192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.77
      iface[:gateway] = r.split(" ").first    # the first without proto kernel should show the actual gateway:  192.168.1.1 dev eth0  scope link  metric 1024 
      break # we only care about the first one
    end
  end

  # get the link state
  link = `ip link sh #{name}`
  if $?.success?
    link = link.lines.first
    linkup = link.split(" ")[2].include?(",UP") # this is the part: <BROADCAST,MULTICAST,UP,LOWER_UP>
    stateup = link.include?("state UP")         # this just searches the first line
    iface[:enabled] = linkup && stateup
  end

  # pull the DNS namservers
  iface[:dns1], iface[:dns2] = *File.read('/etc/resolv.conf').lines.grep(/^nameserver \d+\./)[0..1].map {|l| l.split(" ")[1].strip }

  ifaces << iface
end

puts JSON.pretty_generate(ifaces)