A single file
Encrypt and decrypt:
openssl aes-256-cbc -salt -in file -out file.aes
openssl aes-256-cbc -d -salt -in file.aes -out file
Note that the file can of course be a tar archive.
tar and encrypt a whole directory
tar -cf - directory | openssl aes-256-cbc -salt -out directory.tar.aes
openssl aes-256-cbc -d -salt -in directory.tar.aes | tar -x -f -
tar zip and encrypt a whole directory
tar -zcf - directory | openssl aes-256-cbc -salt -out directory.tar.gz.aes
openssl aes-256-cbc -d -salt -in directory.tar.gz.aes | tar -xz -f -
Password from file option
-pass file:<passwdfile>