Unbuffered pipe(2)'s?

[Gavin Bell]

Is there any way to turn off the PIPE_MAX-long buffer used for pipes?
I need simple unbuffered, one-way communication.

Details on what I'm trying to do:

Essentially, I have the following situation:

filter1 < file_of_data | filter2

... where filter1 understands some of the data in in file_of_data to
be "present this text to the user now, so they know what is going on"
and filter2 understands the rest of the data (which is things like
"Pause for 3 seconds; now display this anti-aliased wireframe
airplane... etc").

Pipes are perfect for this, except that they are buffered, so filter1
is not synchronized with filter2.

I would prefer a portable (at least SYSV), non-hack solution.
--
--gavin     (gavin at sgi.com,  (415)335-1024)