I am trying to install an astronomical software package GILDAS: https://www.iram.fr/IRAMFR/GILDAS/
Following the instructions on the Download page of that web, I installed it with "sudo port install". When I tried to launch it after installation with the command "greg", I got very the same error message:
(<unknown>:29409): Gtk-WARNING **: cannot open display:
I deem this an opposite case as in above discussions, because I used sudo to install the software but are trying to use it from my normal user account. How should I do in this case? How can I diagnose the cause?
I am using MAC OS X El Capitan.