Actually, copyfile is the proposed open/read/write/close interface.
getfile is the current interface, and it seems to be a contentious
one. I've discussed it quite a bit with Jes here and in the last
couple RFCs. I think the current course is that we'll end up ditching
viewfile/viewdmesg in favor of copyfile, and that we should do it now
rather than later.
The upshot is that "viewfile <remote>" is basically equivalent to:
copyfile_open <remote> /dev/stdout -> fd_handle;
copyfile_read fd <offset=0> <count=<MAX_CHUNK_SIZE>;
copyfile_close fd_handle".