text: /* test 4 */
  
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <fcntl.h>
  #include <signal.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <stdio.h>
  #include <string.h>
  
  pid_t pid0, pid1, pid2, pid3;
  int s, i, fd, nextb, errct = 0;
  char *tempfile = "test4.temp";
  char buf[1024];
  extern int errno;
  
  _PROTOTYPE(int main, (void));
  _PROTOTYPE(void subr, (void));
  _PROTOTYPE(void nofork, (void));
  _PROTOTYPE(void quit, (void));
  
  int main()
  {
    int k;
  
    printf("Test  4 ");
    fflush(stdout);		/* have to flush for child's benefit */
  
    system("rm -rf DIR_04; mkdir DIR_04");
    chdir("DIR_04");
  
    creat(tempfile, 0777);
    for (k = 0; k < 20; k++) {
  	subr();
    }
    unlink(tempfile);
    quit();
    return(-1);			/* impossible */
  }
  
  void subr()
  {
    if ( (pid0 = fork()) != 0) {
  	/* Parent 0 */
  	if (pid0 < 0) nofork();
  	if ( (pid1 = fork()) != 0) {
  		/* Parent 1 */
  		if (pid1 < 0) nofork();
  		if ( (pid2 = fork()) != 0) {
  			/* Parent 2 */
  			if (pid2 < 0) nofork();
  			if ( (pid3 = fork()) != 0) {
  				/* Parent 3 */
  				if (pid3 < 0) nofork();
  				for (i = 0; i < 10000; i++);
  				kill(pid2, 9);
  				kill(pid1, 9);
  				kill(pid0, 9);
  				wait(&s);
  				wait(&s);
  				wait(&s);
  				wait(&s);
  			} else {
  				fd = open(tempfile, O_RDONLY);
  				lseek(fd, 20480L * nextb, 0);
  				for (i = 0; i < 10; i++) read(fd, buf, 1024);
  				nextb++;
  				close(fd);
  				exit(0);
  			}
  		} else {
  			while (1) getpid();
  		}
  	} else {
  		while (1) getpid();
  	}
    } else {
  	while (1) getpid();
    }
  }
  
  void nofork()
  {
    int e = errno;
    printf("Fork failed: %s (%d)\n",strerror(e),e);
    exit(1);
  }
  
  void quit()
  {
  
    chdir("..");
    system("rm -rf DIR*");
  
    if (errct == 0) {
  	printf("ok\n");
  	exit(0);
    } else {
  	printf("%d errors\n", errct);
  	exit(1);
    }
  }
  