how to enable dmenu autocompletion?

Question

How to enable autocompletion for command options in dmenu? For example with the default options

systemctl poweroff

autocompletes only systemctl and not poweroff

Answer 1

From man dmenu:

DESCRIPTION
   dmenu is a dynamic menu for X, which reads a list of newline-separated  items  from  stdin.   When  the  user
   selects  an  item  and presses Return, their choice is printed to stdout and dmenu terminates.  Entering text
   will narrow the items to those matching the tokens in the input

What you want to do is outside the scope of dmenu, presumably you want something that operates more like a terminal emulator (which inherits whatever fancy autocompletion features that your shell has).

You could add systemctl poweroff to your command list manually, but I suspect that isn't quite what you want.