dio_open() opens a file and returns a new file descriptor for it.
The opened file.
The flags parameter can also include any combination of the following flags:
O_CREAT - creates the file, if it doesn't
O_EXCL - if both,
O_EXCL are set, dio_open()
fails, if the file already exists.
O_TRUNC - if the file exists, and its opened
for write access, the file will be truncated to zero length.
O_APPEND - write operations write data at the
end of the file.
O_NONBLOCK - sets non blocking mode.
If flags is
mode will set the mode of the file
O_RDONLY - opens the file for read access.
O_WRONLY - opens the file for write access.
O_RDWR - opens the file for both reading and
$fd = dio_open('/dev/ttyS0', O_RDWR | O_NOCTTY | O_NONBLOCK);