Introduction to System V IPC

A comprehensive, deep-dive guide to Inter-Process Communication using Shared Memory and Semaphores in C/C++. Build a complete Producer-Consumer system from scratch.

IPC Flow - Process A (Producer) sends data through Shared Memory to Process B (Consumer)

Producer and consumer communicate via shared memory with semaphore synchronization

See the Code Start Learning

What is System V IPC?

Inter-Process Communication (IPC) allows separate programs running on the same computer to share data and coordinate their actions. Unlike threads (which share memory automatically), processes have completely isolated memory spaces—they need special mechanisms to communicate.

System V IPC is a classic UNIX API (dating back to 1983) that provides three powerful primitives:

Shared Memory: Multiple processes access the same region of RAM—the fastest form of IPC since data isn't copied
Semaphores: Kernel-managed counters that synchronize access and prevent race conditions
Message Queues: Not covered here, but allow processes to send structured messages

Why learn this? While newer APIs exist (POSIX shared memory, pthread semaphores), System V IPC remains widely used in:

Database systems (PostgreSQL, Oracle)
High-performance computing and scientific applications
Legacy systems that need maintenance
Understanding how the kernel manages inter-process resources

Prerequisites

This tutorial assumes:

Basic C/C++ knowledge: Variables, functions, pointers, structs, loops
Linux/Unix command line: Navigating directories, running commands, using terminal
Compilation basics: Using g++ or make

If you're rusty on C pointers and structs, check out Part 4: C/C++ Essentials for a refresher.

Learning Path

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Part 1: Core Concepts

Understand IPC fundamentals, the Producer-Consumer problem, and the three-semaphore solution with circular buffers.

Start Here →

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Part 2: Shared Memory

Learn shmget, shmat, shmdt, shmctl. Map memory regions between processes for ultra-fast communication.

Shared Memory →

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Part 3: Semaphores

Master semget, semop, semctl. Synchronize processes, prevent race conditions, and coordinate access.

Semaphores →

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Part 4: C Essentials

Pointers, structs, arrays, string functions, time handling, ANSI escape codes, and random numbers in C++.

C Essentials →

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Part 5: Implementation

Build a complete Producer-Consumer system with commodity price generation and real-time dashboard display.

Full Code →

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Part 6: Best Practices

Error handling, signal handlers for cleanup, resource management, and common pitfalls to avoid.

Best Practices →

The Project: Commodity Price Dashboard

Throughout this tutorial, you'll build a complete system where:

Multiple Producers generate commodity prices (GOLD, SILVER, CRUDEOIL, etc.) using normal distribution
One Consumer displays a real-time dashboard with prices, moving averages, and trend indicators
Shared Memory provides the communication channel between processes
Three Semaphores ensure safe synchronization without race conditions or deadlocks

System Overview - Three producers, shared memory circular buffer, three semaphores, and consumer dashboard

Complete system showing producers, shared memory buffer, semaphores, and consumer

Quick Start

Want to see it run before diving into the theory? Here's how:

bash — producer-consumer demo

$ cd code/ $ make g++ -o producer producer.cpp g++ -o consumer consumer.cpp # Terminal 1: Start the consumer (creates IPC resources) $ ./consumer 8 # Terminal 2: Start a producer $ ./producer GOLD 2000.0 5.0 500 8 # Terminal 3: Start another producer $ ./producer SILVER 25.0 0.5 300 8 # Watch the dashboard update in real-time! # Press Ctrl+C in consumer to clean up and exit

Then come back to Part 1 to understand how it works.