1 2 3 4 5 6 7 8 | for n in `ls /var/lib/apt/lists/*gpg`; do echo "$n" ; gpg --list-packets "$n" | grep FB510D557CC3E840; done Ourput: ; gpg --list-packets "$n" | grep FB510D557CC3E840; done /var/lib/apt/lists/archive.canonical.com_dists_trusty_Release.gpg /var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_trusty_Release.gpg /var/lib/apt/lists/in.archive.ubuntu.com_ubuntu_dists_trusty_Release.gpg /var/lib/apt/lists/www.scootersoftware.com_dists_stable_Release.gpg |