A/UX® System Administrator's Reference Sections 1M, 7, and 8

mtio(7) rntio(7)
NAME
mt i 0 - interface conventions for magnetic tape devices
DESCRIPTION
The rnt i 0 library allows applications to access tape devices using
a standard interface.
While the general read, write, and seek operations are part of the
standard I/O library, additional library resources are required to
add support for tape devices. The rnt i 0 library helps provide a
fairly device-independent way to perform additional operations,
such as rewind, that are common to tape drives, but not common
to other types of devices.
There are several system -dependent parameters that this generic
device interface uses. The most important is a standard I/O block
size, BLKDEV IOSIZE, which is defined in .
For NUX, thiS value is 1024. The commands that typically are
used in conjunction with a tape drive, such as tar(1), ultimately
generate requests to read and write 1024-byte blocks when the
tape devices are specified for either input or output. However, a
peculiarity of the Apple SC 40 Tape Backup is that it can only
read and write in blocks of 8192 bytes, requiring a specially formulated
user command line (see tc(7) and tcb(l)).
The rntio library moderates device I/O when output is sent to or
obtained from the device files in / dev / rrnt.
IOCTLS
When manipulating the tape cartridge device more directly
through your own programs, or through programs such as rnt(l),
tape-specific operations are supported through mtio ioctls. With
a few exceptions, these generic operations are shared by all tape
drives. One exception is the "format" ioctl (MTFORMAT), which
is available for the Apple SC 40 Tape Backup only; in general,
this is not a function of reel tape drives, such as 9-track tape
drives. Other exceptions that apply to the tape cartridge unit are
described in tc(7). The following is a list of mtio ioctls, and
their associated subcommands. For complete details about the
data structures, see .
ioctl ifd, MTIOCGET, *mtget)
This tape ioctl causes. the tape unit to return the status of the
tape drive, returning values in mtget.
February, 1990
RevisionC
1