#include <stdio.h>	/* printf, etc */
#include <sys/types.h>  /* almost always need this with system programming */
#include <unistd.h>	/* fork, getpid, getppid */

/* Another fork test program - this one includes a command line option that 
   specifies which process should call sleep

   if "-c" is specified the child sleeps, otherwise the parent sleeps


 */

int main(int argc, char **argv) {
  pid_t childpid;

  if (argc!=2) {
    printf("usage: %s (-p|-c)\n",argv[0]);
    exit(0);
  }
  if (childpid = fork()) {
    /* fork returns child's pid in the parent - this is parent only code */
    if (strcmp(argv[1],"-c")!=0) {
      /* parent sleeps */
      sleep(1);
    }
    printf("I am the parent, my pid is %u\n",getpid());
    printf("My child's pid is (or was) %u\n",childpid);
  } else {
    /* fork returned 0 - this is child only code */
    if (strcmp(argv[1],"-c")==0) {
      /* child sleeps */
      sleep(1);
    }
    printf("I am the child, my pid is %u\n",getpid());
    printf("My current parent's pid is %u\n",getppid());
  }
  return(0);
}