In Chapter 8, we described the process control primitives and saw how to work with multiple processes. But the only way for these processes to exchange information is by passing open files across a
fork or an
exec or through the file system. We’ll now describe other techniques for processes to communicate with one another: interprocess communication (IPC).
In the past, UNIX System IPC was a hodgepodge of various approaches, few of which were portable across all UNIX system implementations. Through the POSIX and The Open Group (formerly X/Open) standardization efforts, the situation has since improved, but differences still exist. Figure 15.1 summarizes the various forms of IPC that are supported ...