> My mistake, I forgot to mention the most
> important thing, the scheme has to change,
> it cannot be a master slave relationship.

Why not?


> So if I can set up a pipe from P1 (Process1)
> to P2 form P2 to P3 ...Pn-1 to Pn and then
> another pipe for each process (each process
> has two pipes) to the output file, is there a
> way to coordinate this?

Two processes can only communicate through a pipe if it was created by a common parent (or one of them is the parent itself). The pipes have to be set up by the parent, and you must also make them aware of their position in this line of pipes, for example by writing it to a counter before performing a fork().

Also, if you choose to use pipes after all, you don't have to communicate the results back again. The final child in the line could write to the first pipe so you get a circle.

> Also when you say "Each child can block on
> its pipe" can you expand a bit

What's to expand? I repeated what you said in your post: That the read will block if there is no data.

I think it's time for you to research the rest of your solution on your own now.