Resume SCP transferring

Tip from http://www.linuxquestions.org/questions/linux-networking-3/scp-resume-aborted-download-290836

If the following command aborted,
$ scp file_to_transfer user@remotehost:/path/remote_file

then use rsync to resume:
$ rsync --partial file_to_transfer user@remotehost:/path/remote_file

And
$ export RSYNC_RSH=ssh
to use ssh as the transport layer.