ASSIGN(C) UNIX System V
Name
assign, deassign - assigns and deassigns devices
Syntax
assign [ -u ] [ -v ] [ -d ] [ device ] ...
deassign [ -u ] [ -v ] [ device ] ...
Description
assign attempts to assign device to the current user. The
device argument must be an assignable device that is not
currently assigned. An assign command without an argument
prints a list of assignable devices along with the name of
the user to whom they are assigned.
deassign is used to ``deassign'' devices. Without any
arguments, deassign will deassign all devices assigned to
the user. When arguments are given, an attempt is made to
deassign each device given as an argument.
With these commands you can exclusively use a device, such
as a tape drive or floppy drive. This keeps other users
from using the device. They have a similar effect as
chown(C) and chmod(C), although they only act on devices in
/dev. Other aspects are discussed further on.
Available options include:
-d Performs the action of deassign. The -d option can be
embedded in device names to assign some devices and
deassign others.
-v Gives verbose output.
-u Suppresses assignment or deassignment, but performs
error checking.
The assign command will not assign any assignable devices if
it cannot assign all of them. deassign gives no diagnostic
if the device cannot be deassigned. Devices can be
automatically deassigned at logout, but this is not
guaranteed. Device names can be just the beginning of the
device required. For example,
assign fd
should be used to assign all floppy disk devices. Raw
versions of device will also be assigned, e.g., the raw
floppy disk devices /dev/rfd? would be assigned in the above
example.
Note that in many installations the assignable devices such
as floppy disks have general read and write access, so the
assign command may not be necessary. This is particularly
true on single-user systems. Devices supposed to be
assignable with this command should be owned by the user
asg. The directory /dev should be owned by bin and have
mode 755. The assign command (after checking for use by
someone else) will then make the device owned by whoever
invokes the command, without changing the access
permissions. This allows the system administrator to set up
individual devices that are freely available, assignable
(owned by asg), or nonassignable and restricted (not owned
by asg and with some restricted mode).
Note that the first time assign is invoked, it builds the
assignable devices table /etc/atab. This table is used in
subsequent invocations to save repeated searches of the /dev
directory. If one of the devices in /dev is changed to be
assignable or unassignable (i.e., owned by asg), then
/etc/atab should be removed (by the super-user) so that a
correct list will be built the next time the command is
invoked.
Files
/etc/atab Table of assignable devices
/dev/asglock File to prevent concurrent access
Diagnostics
Exit code 0 returned if successful, 1 if problems, 2 if
device cannot be assigned.
(printed 2/15/90) ASSIGN(C)