fusl/src/ipc/ftok.c

#include <sys/ipc.h>
#include <sys/stat.h>

key_t ftok(const char* path, int id) {
  struct stat st;
  if (stat(path, &st) < 0)
    return -1;

  return ((st.st_ino & 0xffff) | ((st.st_dev & 0xff) << 16) |
          ((id & 0xff) << 24));
}