Extract only spent private keys from a BitAddress/LiteAddress text file

filter_bitaddress.bash

# This means to build an array () based on line breaks in the file
# allowing us to use it with a for loop
LFS='
'
# btcaddrs contains addresses that are actually used

addresses=($(cat btcaddrs.txt))
# filter the bitaddress file btc.txt to only contain used addresses
# then spit out the un-quoted private keys
(for a in $addresses; do grep $a btc.txt; done) | awk '{ split($0,a,","); print a[3] }' | tr -d '"'