The read_vtoc() function returns the VTOC (volume table of contents) structure that is stored on the disk associated with the open file descriptor fd.

The write_vtoc() function stores the VTOC structure on the disk associated with the open file descriptor fd.

The fd argument refers to any slice on a raw disk.

Upon successful completion, read_vtoc() returns a positive number indicating the slice index associated with the open file descriptor. Otherwise, it returns a negative number indicating one of the following errors:

VT_EIO

An I/O error occurred.

VT_ERROR

An unknown error occurred.

Upon successful completion, write_vtoc() returns 0. Otherwise, it returns a negative number indicating one of the following errors:

VT_EIO

An I/O error occurred.

VT_ERROR

An unknown error occurred.

VT_EINVAL

The VTOC contains an incorrect field.

See attributes(5) for descriptions of the following attributes:

fmthard(1M), format(1M), prtvtoc(1M), ioctl(2), attributes(5), dkio(7I)

The write_vtoc() function cannot write a VTOC on an unlabeled disk. Use format(1M) for this purpose.