unix <-> dos FIFOS

Leslie Mikesell les at chinet.chi.il.us
Sat Oct 7 05:42:25 AEST 1989

Has anyone tried creating FIFOs (named pipes) under unix and accessing
them from DOS either under VP/ix or through AT&T's Starlan DOS SERVER?
I can think of some good uses for this, but am not quite sure how
to control the behaviour.  Under Simultask (VP/ix) writes from dos
seem to block appropriately, but reads do not work as (I) expected
unless something else has the pipe open for writing.  If you switch out
of the dos virtual terminal while a program is waiting to read a fifo
with no writer, the read terminates with an error. If the writer opens
the fifo after the reader, both processes seem to block forever.  If
some process has the fifo open for writing (I used "sleep 3000 < fifo"
to test) before the reader opens on the DOS side, everything works like
it would under unix.
Under the Starlan DOS Server, writing to a fifo does not block at all
so the writing program gets an error if it starts before the reader
or gets ahead of it (and I was really hoping to make a DOS backup
program that just wrote to a pipe over the net to a unix process copying
to the tape drive....).  I haven't tried reading on the PC side yet
(my PC monitor is off being repaired at the moment.
This would be an *extremely* handy mechanism if it worked, since the DOS
programs just think they are writing to normal files and require no
changes and the unix programs on the other end can provide all kinds
of magic.

Les Mikesell
  les at chinet.chi.il.us

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