show_dhcp_leases.rb

#!/usr/bin/env ruby
require 'date'
require 'time'

LEASES = '/var/lib/dhcpd/dhcpd.leases'

def parse_lease_state(lease_state, lines)
  state = {}

  while (l = lines.shift) != nil
    if l =~ /\s*\}\s*/
      lease_state.merge!(state)
      return
    end

    if l =~ /^\s*ends \d+ (.+);/
      t_now = DateTime.now
      t_end = DateTime.parse($1)
      return if t_end < t_now
      state[:lease_end] = t_end.new_offset(t_now.offset)
    end

    if l =~ /^\s*binding state ([a-z]+)/
      state[:state] = $1
    end

    if l =~ /^\s*hardware ethernet (.+);/
      state[:macaddr] = $1
    end

    if l =~ /^\s*client-hostname "(.+)";/
      state[:hostname] = $1
    end
  end
end

lease_state = {}

open(LEASES) do |io|
  lines = io.readlines
  while (l = lines.shift) != nil
    if l =~ /lease (\d+\.\d+\.\d+\.\d+) \{/
      ipaddr = $1
      lease_state[ipaddr] ||= {}
      parse_lease_state(lease_state[ipaddr], lines)
    end
  end
end

puts "addr_________ expire_____________ leased to_________________________"

lease_state.keys.sort.each do |ipaddr|
  s = lease_state[ipaddr]
  next if s.keys.size == 0
  t = s[:lease_end].strftime('%Y-%m-%d %H:%M:%S')
  puts "#{ipaddr % "%-16s"} #{t} #{s[:macaddr]} #{s[:hostname]}"
end