preadv

Reads from a file descriptor into a number of mutable bytes-like objects.

Combines the functionality of readv() and pread().  As readv(), it will
transfer data into each buffer until it is full and then move on to the
next buffer in the sequence to hold the rest of the data.  Its fourth
argument, specifies the file offset at which the input operation is to
be performed.  It will return the total number of bytes read (which can
be less than the total capacity of all the objects).

The flags argument contains a bitwise OR of zero or more of the
following flags:

- RWF_HIPRI
- RWF_NOWAIT
- RWF_DONTCACHE

Using non-zero flags requires Linux 4.6 or newer.