Terminal command to sync two directories on separate drives?

[131215]

What terminal command can I use to sync two directories. One is on the local HDD. The other one will be on flash drive or SD card?

 

[MacUser2525]

rsync -avP /path/to/first/directory_to_be_synced /path/to/second/ if there are spaces in the path then they need to be escaped or a " put around the path. rsync -avP /path/to/first/directory\ to\ be\ synced /path/to/second/ or rsync -avP "/path/to/first/directory to be synced" /path/to/second/.