- if (strchr(mode, '+')) flags = O_RDWR;
- else if (*mode == 'r') flags = O_RDONLY;
- else flags = O_WRONLY;
- if (strchr(mode, 'x')) flags |= O_EXCL;
- if (*mode != 'r') flags |= O_CREAT;
- if (*mode == 'w') flags |= O_TRUNC;
- if (*mode == 'a') flags |= O_APPEND;