Meaning of PROBE-FILE for direction output

[Rob MacLachlan <RAM@CMU-CS-C.ARPA>]

    I don't think that either of the problems of a non-opening probe
for output files that you mention are important.

    The problem of the result only being valid for an arbitrarily
short period of is not unique to this function.  When opening for
input, the file could be deleted or opened in a read-exclusive fashion
between the probe-file and any open attempt.

    I'm not quite sure what sort of problem you are referring to in
the second case.  Are you talking about the business of the version
number not being known, or what?  The function I propose would
probably return a null version, since that could not be known.

  Rob