#include <stdio.h>
#include <stdlib.h>     /* for perror, EXIT_SUCCESS, EXIT_FAILURE, system */
#include <unistd.h>     /* for fork, getpid, getppid */
#include <sys/wait.h>   /* for WIFEXITED and WEXITSTATUS */

int main(int argc, char **argv)
{
	char buffer[1000];
	int status;
	int s;
	pid_t p;

	const pid_t pid = fork();
	if (pid < 0) {
		perror(argv[0]);
		return 1;
	}

	if (pid == 0) {
		/* Arrive here if I am the child. */
		return EXIT_SUCCESS;   /* Turn into a zombie immediately. */
	}

	/* Arrive here if I am the parent. */
	sleep(1);   /* Give the child time to turn into a zombie. */

	printf("My PID is %d and my child's PID is %d.\n", getpid(), pid);
	/* minus lowercase L for "long" */
	sprintf(buffer, "ps -l -p %d -p %d", getpid(), pid);
	system(buffer);

	p = wait(&status);   /* Harvest the zombie. */
	if (p != pid) {
		fprintf(stderr, "%s: my child is %d, not %d.\n", argv[0], pid, p);
		return 2;
	}

	if (!WIFEXITED(status)) {
		fprintf(stderr, "%s: parent didn't receive exit status from child.\n",
			argv[0]);
		return 3;
	}

	s = WEXITSTATUS(status);
	if (s != EXIT_SUCCESS) {
		fprintf(stderr,
			"%s: parent received exit status %d instead of %d from child.\n",
			argv[0], s, EXIT_SUCCESS);
		return 4;
	}

	return EXIT_SUCCESS;
}