Question

I need my parent and child process to both be able to read and write the same variable (of type int) so it is “global” between the two processes.

I’m assuming this would use some sort of cross-process communication and have one variable on one process being updated.

I did a quick google and IPC and various techniques come up but I don’t know which is the most suitable for my situation.

So what technique is best and could you provide a link to a noobs tutorial for it.

Thanks.

Answer 1

Since you are mentioning using fork(), I assume that you are living on a *nix-System

From Unix.com

The primary way to share data between
processes using UNIX IPCs are:

(1) Shared memory;

(2) Sockets:

There are other UNIX IPCs including

(3) Message Queues.

(4) Semaphores;

(5) Signals.

Your best bet (for IPCs) is to use
shared memory segments, based on your
post. You might need to use semaphores
to insure that the shared memory
operations are atomic.

A tutorial on forking and shared memory is on dev shed:

http://forums.devshed.com/c-programming-42/posix-semaphore-example-using-fork-and-shared-memory-330419.html

another more in-depth description of using multithreading (if appilcable for your application) can be found here:

https://computing.llnl.gov/tutorials/pthreads/