rsync

rsync is useful for repeated directory updates because it can send differences rather than recopy a whole changed file over the network. Specify a source and destination, either locally or with one remote endpoint reached through a remote shell or rsync daemon. Remote transfers require rsync at both ends. A trailing slash on the source means copy its contents instead of adding the directory itself. Preview a new job with --dry-run, especially before using --delete, which removes extra files from the receiving directories. The manual does not support copying between two different remote hosts in one invocation.