Description:

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.