L-1.8: Fork System call with Example | Fork() system call questions

Introduction

This tutorial provides a comprehensive guide on the fork system call in operating systems, specifically focusing on its usage and implications. The fork system call is essential for creating processes in Unix-like operating systems, and understanding it is crucial for various competitive exams and college courses.

Step 1: Understanding the Fork System Call

• The fork system call is used to create a new process by duplicating the existing process.
• The new process created is called the child process, while the original is referred to as the parent process.
• Key points about fork():
  • Returns a zero value to the child process.
  • Returns the child's PID (Process ID) to the parent process.
  • If fork() fails, it returns a negative value.

Step 2: Analyzing the Use of Fork

• Fork is commonly used for:
  • Creating multiple processes to handle tasks concurrently.
  • Running different programs or tasks simultaneously.
• Practical usage scenarios include server applications where each request is handled by a separate process.

Step 3: Writing a Simple Program with Fork

Here's an example program that demonstrates the use of fork:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main() {
    int pid = fork(); // Create a new process

    if (pid < 0) {
        // Error occurred
        fprintf(stderr, "Fork failed.\n");
        return 1;
    } else if (pid == 0) {
        // This block is executed by the child process
        printf("This is the child process.\n");
    } else {
        // This block is executed by the parent process
        printf("This is the parent process. Child PID is %d.\n", pid);
    }
    
    return 0;
}

• Compile the program using gcc -o fork_example fork_example.c.
• Run it with ./fork_example to see the output of both parent and child processes.

Step 4: Understanding Process States

• After a fork, two processes exist:
  • Parent Process: Continues execution and can perform tasks.
  • Child Process: A duplicate of the parent, executing the same code but can run independently.
• Common states for processes include:
  • Running: Actively executing.
  • Waiting: Waiting for resources.
  • Terminated: Finished execution.

Step 5: Common Pitfalls and Tips

• Always check the return value of fork() to handle errors properly.
• Be cautious of resource leaks by ensuring child processes terminate after completing their tasks.
• Use wait() or waitpid() in the parent process to prevent zombie processes.

Conclusion

Understanding the fork system call is vital for process management in operating systems. By mastering this concept, you'll be better equipped for exams and practical applications in programming. Consider exploring more advanced topics like process synchronization and inter-process communication as a next step.