You may or may not remember Xeyes, a demo program that came with (and, as far as I know, still comes with) the X window system. Its purpose was to draw a pair of eyes that followed your mouse cursor:
In the programming language of your choice, shut down the machine that your code was executed on.
No shutting down by resource exhaustion (e.g.: forkbomb to force shutdown)
You are ...
At runtime, keep prompting for a line of input until the user inputs something (other than an empty newline), i.e. does not just press Enter or OK. Output or result is neither required nor prohibited.
In: a string without line breaks*
Allow the user to edit and submit the line
Out: the modified string (optionally with a trailing linebreak)
The line editor must at minimum allow the user to:
move a ...