rsa2048/C7927B82 2015-08-30
rsa2048/FB2D99F9 2015-08-30

grep -o -P 'rsa.{3,13}'

rsa2048/FB2D99F9

gpg2 --list-keys | grep -o -P 'rsa.{3,13}' | sort | uniq -d
 rsa2048/2642B5CD
 rsa2048/DF6AA92A

echo 'rsa2048/2642B5CD' | grep -o -P '(?<=rsa2048/)[[:xdigit:]]{8}'

echo 'rsa2048/2642B5CD' | grep -o -P 'rsa.{3,13}' | cut -d/ -f2

gpg2 --with-colons --list-keys | grep '^pub:[[:alpha:]]:2048:1:' | cut -d: -f5