I am running an application with command $ grails run-app which prints log in terminal like below.

What I want is search a particular text (say user authorities) in this log so that I can verify further. One way using Logging Apis to write in text file but I want to search it in a terminal at the moment.
I found similar question at how to make search a text on the terminal directly which suggests screen command, but I have no idea how screen works in this case. I tried $ screen grails run-app but couldn't move ahead.
I can see screen lists with
prayag@prayag:~/zlab/nioc2egdelonk$ screen -list There is a screen on: 8076.pts-2.prayag (10/06/2013 12:13:25 PM) (Attached) 1 Socket in /var/run/screen/S-prayag. 