From the safecat README:

  safecat is an implementation of D. J. Bernstein's maildir algorithm.
  It can be used to write mail messages to a qmail-style maildir, or to
  write data to a "spool" directory reliably. There are no lockfiles with
  safecat, and nothing is left to chance. If safecat returns a successful
  exit status, then you can be (practically) 100% sure your data is
  safely committed to disk. Further, if data is written to a directory
  using safecat (or other implementations of the maildir algorithm),
  then every file in that directory is guaranteed to be complete. If
  safecat fails to write all of the data, there will be no file at all
  in the destination directory.

  Of course, you know that such a thing cannot be: between UNIX and
  the different hardware options available, a 100% guarantee is not
  possible. However, safecat takes every precaution possible in writing
  your data.

Author:		Len Budney <lbudney@pobox.com>
WWW:		http://www.nb.net/~lbudney/linux/software/safecat.html