IPC

Inter-process communication, or IPC, refers to the set of mechanisms that allow separate processes to exchange data and coordinate their actions within a computer system. IPC enables multitasking, modular software design, resource sharing, and synchronization across process boundaries.

Common IPC mechanisms include shared memory, which lets processes map the same memory region for fast data exchange, typically using synchronization primitives like semaphores or mutexes to prevent race conditions. Message-based IPC conveys discrete messages between processes. It includes pipes (anonymous or named), POSIX and System V message queues, and sockets, including UNIX domain sockets for local communication and Internet sockets for networked communication.

Pipes are often used for simple parent-child communication and provide one-way data flow; named pipes extend this across unrelated processes. Shared memory offers high performance but requires careful synchronization to avoid data corruption. Message queues provide queued, structured communication with separate sending and receiving endpoints. Sockets enable both local and networked communication, spanning stream-oriented (TCP) and datagram (UDP) models. Remote procedure calls (RPC) and higher-level abstractions enable procedures on one process to appear as local calls on another.

Security, access control, and performance considerations influence the choice of IPC method. Shared memory offers low latency but requires custodianship of synchronization; message passing avoids shared state but can incur data copies and context switches.

Operating systems provide IPC infrastructure. Unix-like systems offer pipes, shared memory, semaphores, and message queues, while Windows provides named pipes, memory-mapped files, and RPC services. In distributed systems, IPC concepts expand to include remote procedure calls, message queues, and publish–subscribe messaging, complementing localized IPC within a single system.