[O]

1. OPEN_MAX
2. OVERHEAD
3. O_ACCMODE
4. O_APPEND
5. O_CREAT
6. O_EXCL
7. O_MARKER
8. O_NOCTTY
9. O_PLAYER
10. O_RDONLY
11. O_RDWR
12. O_TRUNC
13. O_WRONLY