[o]

[..]
  1. off_t
  2. offsetof
  3. old_stat
  4. old_utsname
  5. oldold_utsname
  6. oom
  7. open
  8. open_aux
  9. open_inode
  10. open_mouse
  11. open_namei
  12. open_qp
  13. operand_selector
  14. options
  15. origin
  16. out_port_type
  17. outb
  18. outb_p
  19. output_byte
  20. outsw
  21. outw
  22. outw_p
  23. overlap
[..]