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Program to create an zombie process

by Anup Maurya
13 minutes read

In this article, we will delve into what a zombie process is, why it occurs, and provide a code example in C to demonstrate its creation.

In the realm of operating systems, processes play a pivotal role in managing the execution of programs. They are essential entities that enable multitasking and parallel execution. However, there is an intriguing phenomenon known as a “zombie process” that can arise during the lifecycle of a process.

What is a Zombie Process?

A zombie process, also referred to as a defunct process, is a process that has completed its execution but still retains an entry in the process table. This entry contains information about the process, such as its process ID (PID) and exit status. Zombie processes are a natural outcome of the parent-child relationship in process management.

The Parent-Child Relationship

In many operating systems, processes can create child processes using the fork() system call. The parent process spawns a new child process, sharing the parent’s resources and memory space. Once the child process finishes executing, it informs the parent about its termination status. However, before the parent retrieves this status using the wait() or waitpid() system call, the child process becomes a zombie.

Why Zombie Processes Occur

Zombie processes emerge due to the need for the parent process to collect exit status information from its child processes. The exit status holds important information about the child process’s termination, such as whether it exited successfully or encountered an error. Until the parent retrieves this information, the child’s process table entry remains, resulting in a zombie process.

Program to create an zombie process

#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

int main() {
    pid_t child_pid = fork();  // Fork returns process ID

    if (child_pid > 0) {
        // Parent process
        sleep(50);  // Parent sleeps for 50 seconds
    } else {
        // Child process
        exit(0);    // Child exits

    return 0;

In this example, the code creates a child process using fork(). In the parent process, the code sleeps for 50 seconds using sleep(), while the child process immediately exits using exit(0). During the sleep period of the parent process, the child process becomes a zombie because its exit status is yet to be collected.


Zombie processes are an interesting aspect of process management in operating systems. They provide a mechanism for parent processes to retrieve exit status information from their child processes. Zombie processes are automatically cleaned up by the operating system when the parent process finally collects the exit status. Understanding zombie processes adds depth to our knowledge of how operating systems manage processes and resources efficiently.

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