I am trying to capture the Desktop ID from xwininfo using:
User@name:~$ DESKTOPID="$ xwininfo -int -name Desktop | head -2 | awk '{print $4}'"
User@name:~$

I then try to see that DESKTOPID has something in it and get:
User@name:~$ printenv DESKTOPID
User@name:~$

I also tried this:
User@name:~$ echo $DESKTOPID

User@name:~$

Please help, what am I doing wrong? Thank you in advance.

Operating System:
Linux version 4.3.0-kali1-amd64 (gcc version 5.3.1 20160101 (Debian 5.3.1-5) ) #1 SMP Debian 4.3.3-5kali4 (2016-01-13)