12.1 Line Editing
If supported, input line editing is active whenever the interpreter
prints a primary or secondary prompt. The current line can be edited
using the conventional Emacs control characters. The most important
of these are: C-A (Control-A) moves the cursor to the beginning
of the line, C-E to the end, C-B moves it one position to
the left, C-F to the right. Backspace erases the character to
the left of the cursor, C-D the character to its right.
C-K kills (erases) the rest of the line to the right of the
cursor, C-Y yanks back the last killed string.
C-underscore undoes the last change you made; it can be repeated
for cumulative effect.