Undo the commands back through a command descriptor
See undo for an introduction to undoing commands.
:ubt :max ; undo back through the most recent command
; (which just means undo the most recent command)
:ubt :x ; same as :ubt :max
:u ; same as :ubt :max with no questions asked
:ubt fn ; undo back through the introduction of fn
; (including all the other events in fn's block)
:ubt 5 ; undo back through the fifth command executed
:ubt (:max -4) ; undo back through the most recent five commands
:ubt (:x -4) ; undo back through the most recent five commands
Ubt takes one argument, a command descriptor, and undoes the
commands from :max (aka :x) through the one
described. See command-descriptor. Pbt will print the commands that ubt will undo. :Oops will undo the undo.
Ubt can cause errors but not queries. To get queries as well, see
ubt?. To get neither errors nor queries, see ubt!..
It is important to remember that a command may create several events. That is, the command that introduces fn1 may also
introduce fn2. Undoing the command that created either of these
will undo them both. The events created by a command constitute
the command's ``block'' and we can only undo entire blocks. Use pcb to print the command block of a command if you wish to see
what will be lost by undoing the command.
Ubt will not undo into ``prehistory''. :Ubt 1 will undo all of
your commands. But :ubt -5 will cause an error, warning you that
:ubt cannot undo system initialization.
See u for how to undo just the latest command. See ubu,
ubu!, and ubu? for how to undo back up to, but not including,
the current command.