How to create a zombie process that cannot be reaped for a few minutes

Question

Could someone suggest me an easy way to create a zombie process that cannot be reaped for a few minutes. The purpose of this is to test parent process for being able to reap zombies processes after they become reapable again.

One case for non-reapable zombies can be found here . I guess there might be easier ways to do so.

OS: Linux

Preferable languages: C/C++

Answer 1

Here's a little program that will cause a zombie to show up in your "ps aux" output for a few minutes. Note the commented-out waitpid() call; if you un-comment that call, the zombie will not show up, as the waitpid() call causes the parent process to claim its dead child.

(Disclaimer: I only tested this under MacOS/X since that's the computer I'm at, but it should work the same under Linux)

#include <stdio.h>
#include <signal.h>
#include <pthread.h>
#include <sys/wait.h>
#include <unistd.h>

int main()
{
   printf("Starting Program!\n");

   int pid = fork();
   if (pid == 0)
   {
      printf("Child process %i is running!\n", getpid());
      sleep(300);  // wait 5 minutes
      printf("Child process %i is exiting!\n", getpid());
      return 0;
   }
   else if (pid > 0)
   {
      printf("Parent process is continuing child's pid is %i...\n", pid);
      sleep(5);  // just for clarity
      printf("Parent process is sending SIGKILL to child process...\n");
      if (kill(pid, SIGKILL) != 0) perror("kill");
      // waitpid(pid, NULL, 0);  // uncomment this to avoid zombie child process

      printf("Parent process is sleeping... ps aux should show process #%i is a zombie now\n", pid);
      sleep(500);  // just for clarity
      printf("Parent process is exiting!\n");
   }
   else perror("fork()");
}