| OddParity | System.Posix System.Posix.Terminal |
| OpenFileFlags | System.Posix System.Posix.IO |
| OpenFileLimit | System.Posix System.Posix.Unistd |
| OutputQueue | System.Posix System.Posix.Terminal |
| openDirStream | System.Posix System.Posix.Directory |
| openEndedPipe | System.Posix |
| openFd | System.Posix System.Posix.IO |
| otherExecuteMode | System.Posix System.Posix.Files |
| otherModes | System.Posix System.Posix.Files |
| otherReadMode | System.Posix System.Posix.Files |
| otherWriteMode | System.Posix System.Posix.Files |
| outputSpeed | System.Posix System.Posix.Terminal |
| ownerExecuteMode | System.Posix System.Posix.Files |
| ownerModes | System.Posix System.Posix.Files |
| ownerReadMode | System.Posix System.Posix.Files |
| ownerWriteMode | System.Posix System.Posix.Files |
