Extract Bluetooth MAC Address: hcitool dev
For you purpose is quite enough grep
hcitool dev | grep -o "[[:xdigit:]:]\{11,17\}"
-o outputs just finded patten
[[:xdigit:]:] mean all hexadecimal digits plus : char
{11,17} the set of chars should be neither less then 11 no more 17 in length
try
awk 'NR>1 { print $2 } ' /home/pi/mario/BT.txt
where
NR>1means skip first row. (NR: Number of record)