Chapter 4. Interprocess Communication

Interprocess communication (IPC) is the sharing of data and synchronization of events among processes. Contrast IPC with networking-based facilities, such as sockets and RPC interfaces, which enable communication over a network link between distributed systems. Early IPC facilities originated in AT&T UNIX System V, which added support for shared memory, semaphores, and message queues around 1983. This original set of three IPC facilities is generally known as System V IPC. Over time, a similar set of IPC features evolved from the POSIX standards, and we now have POSIX semaphores, shared memory, and message queues. The System V and POSIX IPCs use different APIs and are implemented differently in the kernel, although for applications they provide similar functionality.

Other facilities for interprocess communication include memory mapped files (mmap(2)), named pipes (also known as FIFOs), UNIX domain sockets, and the recently added Solaris Doors, which provide an RPC-like facility for threads running on the same system. Each method by which an application can do interprocess communication offers specific features and functionality which may or may not be useful for a given application. It's up to the application developer to determine what the requirements are and which method best meets those requirements.

Our goal here is not to provide a tutorial on programming with these interfaces, although some mention of the APIs is necessary when we describe a feature or functional component. Several texts discuss programming and interprocess communication, most notably, Solaris Systems Programming by Rich Teer and UNIX Network ProgrammingInterprocess Communication, Second Edition, Volume 2, by W. Richard Stevens.