IPC and STREAMS in Unix V.3

[Dave Turner]

In article <117 at amtfocus.UUCP> irab at amtfocus.UUCP (Ira Brenner) writes:
>	I have four main processes running simultaneously (A, B, C, D). Process
>	B needs to communicate with a child (C) and another process, which may
>	or may not be a child, (D). No direct communication between C and D is
>	necessary. Process B also needs to communicate with process A. In 

>	could use a few pointers on how to do it. I don't think any of
>	the other methods of IPC for Unix (shared memory, semephores) are

System V messages will do what you want. Have each process open a message queue
for reading. The other processes can open the same msg queues for writing.
The message could contain the message id if replies are expected (required?).

A set of files can be used to allow the processes to open the msg queues.
Use ftok() (see stdipc(3c) to convert filenames to key-t's for msgget().

Give the files names that make sense to the set of processes.

	/usr/spool/xxx/A	# the msg queue read by process A
	/usr/spool/xxx/B	# the msg queue read by process B
	/usr/spool/xxx/C	# the msg queue read by process C
	/usr/spool/xxx/D	# the msg queue read by process D

Each process should ftok and get its msg queue first. Processes B-D should read
(and wait for) messages. Process only needs to read its msg queue occassionally
and probably should not wait.



-- 
Dave Turner	415/542-1299	{ihnp4,lll-crg,qantel,pyramid}!ptsfa!dmt