I was having problem with SSH X-11 forwarding while I used sudo. I found a solution for it.

$hostname
server4.a.b.edu

First I do:

$ echo $DISPLAY
localhost:10.0

then

$ xauth list
server1.a.b.edu/unix:12  MIT-MAGIC-COOKIE-1  6026864294a0e081ac452e8740bcd0fe
server4.a.b.edu/unix:10  MIT-MAGIC-COOKIE-1  f01fbfe0c0d68e30b45afe3829b27e58

Then I need to do

$ sudo xauth add server4.a.b.edu/unix:10  MIT-MAGIC-COOKIE-1  f01fbfe0c0d68e30b45afe3829b27e58

for sudo to work, for the cookie with my server name and display.

How do I write a bash script to automate this?