2d
without arguments,
invokes a version of the shell that does
not support the 3d file system.
If
arg
does not begin with a
-,
then
2d
executes the command
in an environment which does not support the 3d file system.
If
arg
begines with a
-,
and is not exactly
-,
then
2d
executes
$SHELL
arg...
in an environment which does not support the 3d file system.
If the first argument to
2d
is
+
then all subsequent commands issued from the same environment
until
2d -
will be executed in an environment that does not support
the 3d file system.
All remaining arguments are ignored.