I was SSHed into a remote Linux computer and working on it when I executed Vim command at the shell and nothing happened. It just hung.
I tried opening Vim without any plugins and settings using vim -u NONE -i NONE and it still hung.
I tried opening Vim with logging enabled vim -V and I did not see any error.
To get out of the logging mode, I pressed Ctrl+C when I noticed this message: Opening the X display failed
Why was Vim at the shell dependent on the X display? Not sure, but I am guessing it probably tries to connect to the X clipboard.
In any case, I checked the DISPLAY environment variable and noticed that I had set that up wrongly. I set that to the default value:
$ export DISPLAY=:0.0Vim opened up instantly after this!
Tried with: Vim 8.0 and Ubuntu 18.04