05-28-2010
You're missing my point. You can't connect processes that already exist with anonymous pipes. Therefore the instructions you want, connecting any 3 processes with pipes, simply don't exist.
All of the pipes must be created in the parent first. That way, when it creates children, they will share these pipes, allowing them(and of course the parent) to redirect their I/O through them how they please. To give more detailed instructions I'll need to know which of your processes created which others.
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FORK(2) System Calls Manual FORK(2)
NAME
fork - spawn new process
SYNOPSIS
fork( )
DESCRIPTION
Fork is the only way new processes are created. The new process's core image is a copy of that of the caller of fork. The only distinc-
tion is the fact that the value returned in the old (parent) process contains the process ID of the new (child) process, while the value
returned in the child is 0. Process ID's range from 1 to 30,000. This process ID is used by wait(2).
Files open before the fork are shared, and have a common read-write pointer. In particular, this is the way that standard input and output
files are passed and also how pipes are set up.
SEE ALSO
wait(2), exec(2)
DIAGNOSTICS
Returns -1 and fails to create a process if: there is inadequate swap space, the user is not super-user and has too many processes, or the
system's process table is full. Only the super-user can take the last process-table slot.
ASSEMBLER
(fork = 2.)
sys fork
(new process return)
(old process return, new process ID in r0)
The return locations in the old and new process differ by one word. The C-bit is set in the old process if a new process could not be cre-
ated.
FORK(2)