make_zombie.c

#include <signal.h>
#include <libgen.h>
#include "tlpi_hdr.h"

#define CMD_SIZE 200

int
main(int argc, char *argv[])
{
    char cmd[CMD_SIZE];
    pid_t childPid;

    setbuf(stdout, NULL);  // disable buffering of stdout

    printf("Parent PID=%ld\n", (long) getpid());

    switch (childPid= fork()) {
    case -1:
        errExit("fork");

    case 0:  //Child: immediately exits to become zombie
        printf("Child (PID=%ld) exiting\n", (long) getpid());
        _exit(EXIT_SUCCESS);

        default:  //Parent
        sleep(3); //Give child a chance to start and exit
        snprintf(cmd, CMD_SIZE, "ps | grep %s", basename(argv[0]));
        cmd[CMD_SIZE - 1] = '\0';
        system(cmd);

        // Now send the "sure kill" signal to the zombie

        if (kill(childPid, SIGKILL) == -1)
            errMsg("kill");
        sleep(3);
        printf("After sending SIGKILL to zombie (PID=%ld):\n", (long) childPid;
        system(cmd);

        exit(EXIT_SUCCESS);
    }
}