xfwm4 -V (return code: 1)
(xfwm4:21383): Gtk-WARNING **: cannot open display:
xfwm4 --help (return code: 0)
Usage:
xfwm4 [OPTION?] [ARGUMENTS...]
Help Options:
-h, --help Show help options
--help-all Show all help options
--help-gtk Show GTK+ Options
--help-sm-client Show session management options
Application Options:
--daemon Fork to the background
--compositor=on|off|auto Set the compositor mode
--replace Replace the existing window manager
-V, --version Print version information and exit
--display=DISPLAY X display to use