Major Section: HISTORY
Examples: :ubu :x-3 ; undo the last three commands (same as :ubt :x-2) :ubu (:x -3) ; same as above :ubu fn ; undo back up to, but not including the introduction of fn ; (so fn will continue to be defined) :ubu 5 ; undo back up to, but not including, the fifth command ; executed (leaving the first five commands in place)See command-descriptor.
Ubu takes one argument, a command descriptor, and undoes the
:x) up to, but not including, the
indicated command. See command-descriptor.
Ubu can cause errors or queries. To avoid these, see ubu!.
Also see ubt, which is similar but also undoes the indicated command. As
oops will undo the undo (see oops) and
ubu will not undo into ``prehistory''.
See u for how to undo just the latest command, and see ubt and see ubt! for
how to undo back through (that is, including) the current command.