7. Opening The Device

A generic device has to be opened for read and write access:

        int fd = open (device_name, O_RDWR);

(This is the case even for a read-only hardware device such as a cdrom drive).

We have to perform a write to send the command and a read to get back any results. In the case of an error the return code is negative (see section sec-errorhandling for a complete list).