Backspace in the Terminal

bs.fish

function bs --description 'Backspace over last line'
   set -l EDITED '\e[7m'
   if test -z "$argv"
      # default
      echo -ne -- '\e[A\e[K\e[A'  # up, clear line, up
   else
      set -l N $argv[1]           # -5 to clear five up, 5 to type over fifth line
      if test '+-' = +(string sub -l 1 -- "$N")
         # clear N lines up
         set -l C (seq 0 (string sub -s 2 -- "$N"))
         for T in $C
            echo -ne -- '\e[A\e[K'
         end
         return
      end
      # or type over line N, clearing it first in style
      echo -ne -- '\e['$N'A'$EDITED'\e[K \e['(math -s0 $COLUMNS' - 1')'b\e[G'
      while read -z -n 1 -P '' -l X
         # use Enter/Return to finish typing
         if test \n = "$X"
            echo -ne -- '\e[m'
            break
         end
      end
      # this is just like using N-1 except it's not
      echo -ne -- '\e['$N'B\e[A\e[m'  # N down, up, reset
   end

end

asciinema.org/a/435871
License MIT free to do whatever, yours to fuck up.