The blacklist is stored in the asterisk database (AstDB) but can be easily accessed from the command line using something like
asterisk -x "database show blacklist"
This is a raw dump and isn't much use in this format, we want to strip off the /blacklist/ and the : 1 then trim out the whitespace and loose the number of records. To do this in the shell we'd use
asterisk -x "database show blacklist"|sed "s/\/blacklist\///g"|sed "s/: 1//g"|grep -v dest|grep -v results|sed -e "s/ *$//"
I hope this helps. You can add to the blacklist database by using database put but be careful as there seems to be little in the way of error checking.