Inter-Process Communication (IPC) & System Programming Concepts

Category	Mechanism/Concept	Description	Key Characteristics
Process Control	fork	Creates a new process	Duplicates current process, child continues from fork return
	syslog	System logging service	Sends log messages to system log daemon (e.g., rsyslog)
Anonymous Pipes	pipe	Creates anonymous pipe	Unidirectional, only between related processes
Named Pipes	FIFO	Creates named pipe	Has filesystem entry, works with unrelated processes
Message Queues	msg_queue	System V message queues	Message linked list, supports message types and priorities
I/O Multiplexing	poll	I/O event monitoring	Monitors multiple file descriptors for events, more efficient than select
Shared Memory	shm	Shared memory segments	Fastest IPC, multiple processes access same memory region
Synchronization	semaphore	Process synchronization	Controls access to shared resources, prevents race conditions
Signals	signal	Asynchronous notifications	Sends async events to processes for simple communication and control
Network Communication	socket	Network sockets	Communication between processes on same or different hosts, supports TCP/UDP

Quick Overview

Process Management

• fork: Fundamental system call for process creation
• syslog: System logging interface for application logging

IPC Mechanisms

Mechanism	Relationship	Communication Type	Speed
Anonymous Pipe	Related processes only	Unidirectional	Fast
Named Pipe (FIFO)	Unrelated processes	Unidirectional/Bidirectional	Fast
Message Queue	Unrelated processes	Message-based	Medium
Shared Memory	Unrelated processes	Memory-based	Very Fast
Sockets	Any processes	Stream/Datagram	Variable

Synchronization & Signaling

• Semaphores: Counter-based synchronization
• Signals: Async interrupt-like notifications
• poll: Efficient I/O event monitoring

Use Cases

• Pipes: Command pipelines, simple data transfer
• Message Queues: Structured message passing
• Shared Memory: High-performance data sharing
• Sockets: Network communication, client-server apps
• Signals: Process control, emergency notifications

Common System Calls

fork(), pipe(), mkfifo(), msgget(), semget(), shmget(), 
poll(), signal(), socket(), bind(), connect()