Ed, man! !man ed- GNU Project - Free Software Foundation (FSF)
https://www.gnu.org/fun/jokes/ed-msg.html
Let's look at a typical novice's session with the mighty ed:
golem$ ed
?
help
?
?
?
quit
?
exit
?
bye
?
hello?
?
eat flaming death
?
^C
?
^C
?
^D
?