"echo password | gpg --batch -q --passphrase-fd 0 --cipher-algo AES256 -c /tmp/file.tgz echo password | gpg --batch -q -o /tmp/file.tgz --passphrase-fd 0 --decrypt /tmp/file.tgz.gpg" http://www.linuxscrew.com/2007/08/16/encryption-files-with-gpg-without-user-intervention-batch/