#include <sys/mman.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

struct list {
  char data[500];
  off_t next;
};

int main(int argc, char *argv[argc+1]) {
  size_t len = 10 << 20;
  int fd = open(argv[1], O_CREAT | O_RDWR | O_TRUNC, S_IRUSR);
  if (fd == -1) {
    perror("open");
    return EXIT_FAILURE;
  }

  // grow the file
  if (ftruncate(fd, len) == -1) {
    perror("truncate");
    return EXIT_FAILURE;
  }

  void *base = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  if (base == MAP_FAILED) {
    perror("mmap");
    return EXIT_FAILURE;
  }

  // Do 0..n-1 items
  for (int i = 0; i < 99; i++) {
    void *addr = (void*) (base + (i * sizeof(struct list)));
    off_t next = (off_t) (i+1)* sizeof(struct list);
    struct list *item = (struct list*)addr;
    sprintf(item->data, "i am item # %d",  i);
    item->next = next;
  }

  off_t addr = (off_t) (base + (99 * sizeof(struct list)));
  struct list *item = (struct list*)addr;
  sprintf(item->data, "i am item # 99");

  msync(base, len, MS_SYNC);
  munmap(base, len);
  return EXIT_SUCCESS;
}