Command line recall and editing is very useful for correcting command
errors or to allow your commands to evolve. RLaB provides a command
recall and edit facility modeled on (and sometimes actually using) the GNU
readline facility. If you are familiar with GNU emacs or the GNU bash
shell, then try entering C-p to scroll back through previous commands
(C-p means hold down the control key and press p). If
this is successful, test the standard character and word editing commands
to modify previous entries - if it works, skip to section
.
However, if the word GNU just means ``any of several African antelopes constituting the genus Connochaetes ...''4 but your keyboard does have the arrow keys { ← ↑ ↓ → }, then you might still be able to take advantage of command line recall and editing. Try typing the ↑ key to see if any previous RLaB commands are displayed - if they are, then confirm that ↓ also displays more recent commands and then try horizontal cursor movement with the { ← → } and try some editing with the delete key. Typing C-d ought to delete the character beneath the cursor. When a new command has been created from an old, enter it in the usual way by pressing RETURN. If this has worked for you, skip the remainder of this section (and count yourself lucky that we weren't describing a graphical user interface in one paragraph).
If your keyboard is missing the arrow keys but C-p did cause previous commands to pop up on the RLaB command line, you will find that { ← ↑ ↓ → } are the same as { C-b C-p C-n C-f } - think of b for backwards, p for previous, n for next, and f for forward.
Irrespective of what keystrokes you use for editing, the C-y keystroke will restore text previously deleted. If you were unable to scroll back through any previous commands (that you had just entered), then your RLaB may have been built without command line editing - this is unlucky. As command line editing is such a useful feature, you should consider getting a better version of RLaB if possible.