* pslogin must support `suspend' and `shell' user interupts.

* Interactive mode - prompting before each deletion or change.

* Automatically rerunning with a new starting file on the next volume,
  before exiting.

* James R. Van Zandt <jrv@vanzandt.mv.com>: mirror(1) is good for
  updating a mirror via ftp.  Your program is good for updating it on
  the same machine, or via nfs.  How about a mirror that must be updated
  via sneakernet, like mine?  What I have done is build a third mirror
  on nine zip disks, with a load and a dump mirror script for each.
  However, it is nontrivial to manage (I have to keep each section under
  95 MB, for one thing), and ties up a lot of disks.  The alternative I
  have in mind would work like this: (1) On the mirror machine, run a
  program that examines the state of the mirror directory (file names,
  dates, sizes, etc.) and writes it to removable media. (2) On the
  control machine, compare the state of the control directory with the
  recorded state of the mirror directory.  Write new/changed files to
  removable media.  Also write a file, such as a shell script, to make
  other required changes (file deletions).  (3) On the mirror machine,
  copy the new/changed files from removable media to the mirror
  directory, and make the other required changes.

* What do we do when a username needs two @ in it like with a proxy
  server?

* interpret user and group as strings for mcserv?????