Stan writes:

> Note that the fourth item the hpfcopy programmer passes into HPFOPEN
>  is a 3 ("domain), with value 4 ("makePERM") ... which inserts the file
>  in the directory immediately.  (Also, this was not a POSIX thing...it
>  was in MPE/iX from day 1, IIRC.)

It's this small difference of putting the filename into the directory at the
beginning of the file open process, prior to the actual file copy, and
putting it there at the close of the process that makes all of the difference
between a polling process being "virtually impossible" to screw up (if all of
the necessary precautions are taken) and one that is flat-out impossible to
screw up.

Nonetheless, Ken Hirsch's RENAME is answer -- and the gold standard. By the
time that the RENAME command would have been issued by a job, the source file
would have been built, fully populated and completely stable. Moving the
file's name into a new group's directory would be an absolutely faithful
state variable indicator of the presence of the file. Using Ken's method,
there can never be problems associated with polling simply because there is
no window of vulnerability, no matter how small it might be.

Wirt Atmar

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