Inter-Process Communication (IPC) refers to a set of mechanisms provided by the operating system that allow different processes to communicate with each other and synchronize their actions. This communication is essential for building complex, modular, and concurrent applications.
Processes typically run in separate memory spaces, meaning they cannot directly access each other's data. IPC provides a controlled and safe way to:
Pipes are a simple form of IPC that allow unidirectional data flow between two related processes (typically a parent and child process). A pipe is essentially a buffer in the kernel where one process writes data and another process reads it.
Example Usage: A parent process launching a child process and needing to send commands or receive output from it.
Sockets provide a more versatile communication channel, capable of supporting communication between processes on the same machine (using domain sockets) or across a network (using network sockets). They offer a standard interface for message passing.
Example Usage: Client-server applications, network services (web servers, databases).
Message queues allow processes to send and receive messages asynchronously. Processes can place messages into a queue, and other processes can retrieve them when they are ready. This decouples the sender and receiver.
Example Usage: Decoupling task producers from consumers, implementing event-driven systems.
Shared memory is one of the fastest IPC methods. It involves mapping a region of memory into the address space of multiple processes. Processes can then directly read and write to this shared memory region.
Example Usage: High-performance data sharing between processes, large data transfers.
Semaphores are primarily used for synchronization rather than data transfer. They are signaling mechanisms that control access to shared resources. A semaphore is essentially a counter that processes can increment (signal) or decrement (wait).
Example Usage: Controlling access to a printer spooler, coordinating multiple threads/processes accessing a shared buffer.
Signals are asynchronous notifications sent to a process to indicate that an event has occurred. They are often used for error conditions or to request process termination.
SIGINT (interrupt, typically Ctrl+C) and SIGTERM (terminate).Example Usage: Graceful termination of processes, notifying a process of an external event.
| Mechanism | Primary Use | Complexity | Speed | Data Transfer | Synchronization |
|---|---|---|---|---|---|
| Pipes | Related process communication | Low | Medium | Unidirectional stream | Implicit (via read/write) |
| Sockets | Network/inter-machine/inter-process communication | Medium to High | Medium to High (depends on type) | Bidirectional stream/datagram | Requires explicit handling |
| Message Queues | Asynchronous message passing | Medium | Medium | Message-based | Built-in queuing order |
| Shared Memory | Fastest data sharing | High | Very High | Direct memory access | Requires explicit synchronization (crucial) |
| Semaphores | Synchronization, resource control | Medium | Low (for signaling) | N/A (signaling only) | Primary function |
| Signals | Event notification, error handling | Low to Medium | Low | N/A (event notification) | Implicit upon receipt |