#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>

int main() {
  int fd, result;
  char buf[10];
  if ((fd = open ("/dev/scull", O_WRONLY)) == -1) {
    perror("opening file");
    return -1;
  }
  if ((result = write (fd, "abcdef", 6)) != 6) {
    perror("writing");
    return -1;
  }
  close(fd);
  if ((fd = open ("/dev/scull", O_RDONLY)) == -1) {
    perror("opening file");
    return -1;
  }
  result = read (fd, &buf, sizeof(buf));
  buf[result] = '\0';
  fprintf (stdout, "read back \"%s\"\n", buf); 
  close(fd);
  if ((fd = open ("/dev/scullpipe", O_RDWR)) == -1) {
    perror("opening file");
    return -1;
  }
  if ((result = write (fd, "xyz", 3)) != 3) {
    perror("writing");
    return -1;
  }
  result = read (fd, &buf, sizeof(buf));
  buf[result] = '\0';
  fprintf (stdout, "read back \"%s\"\n", buf); 
  close(fd);
  return 0;
}