gistfile1.txt

# code
#!/usr/bin/env ruby

require 'set'
require 'socket'

Socket.const_set("ETH_P_ALL", 0x0300)

r_sock = Socket.new(Socket::PF_PACKET, Socket::SOCK_RAW, Socket::ETH_P_ALL)
ap_list = Set.new
puts "\n %-24s %s\n\n" % ["BSSID", "ESSID"]
while true
  pkt = r_sock.recvfrom(2048)[0]
  if pkt[26].eql? "\x80"
    unless ap_list.include? pkt[36..42] and pkt[63].ord > 0
      ap_list.add pkt[36...42]
      puts " %-24s %s" % [ pkt[64...64 + pkt[63].ord], pkt[36...42].unpack('H*').first.scan(/.{2}/).join(':').upcase ]
    end
  end
end

# EOF



# output
root@unknown:~# ./rbsniff.rb 

 BSSID                    ESSID

 TNCAP508CAF              9C:97:26:50:8C:AF
 TNCAP508CAF              9C:97:26:50:8C:AF
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 SKY26349                 E8:BE:81:60:66:EE
 TNCAP508CAF              9C:97:26:50:8C:AF
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TNCAP508CAF              9C:97:26:50:8C:AF
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TNCAP508CAF              9C:97:26:50:8C:AF
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TNCAP508CAF              9C:97:26:50:8C:AF
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TNCAP508CAF              9C:97:26:50:8C:AF
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TALKTALK-CAC138          88:53:D4:CA:C1:3A
 TNCAP508CAF              9C:97:26:50:8C:AF
^C./rbsniff.rb:12:in `recvfrom': Interrupt
	from ./rbsniff.rb:12:in `<main>'