Fix machine hostname return null as it value

If your getting null value as your host name, check that both /etc/hosts and /etc/hostname files has the same name to the host, If not put the same name to both file as hostname, Here[1] you can find how to do that.

[1]http://shameerarathnayaka.blogspot.com/2013/03/how-to-change-machine-name-in-ubuntu.html

How to change machine name in Ubuntu 12.04 LTS

Go to the terminal
Type "sudo su" , because you need log into root mode to modify following files.
Now type "gedit /etc/hostname"
Replace new name with old name
Save and close the file

Now type "gedit /etc/hosts"
Replace your new name with old name
    eg : 127.0.1.1 <old name>    -->   127.0.1.1 <new name>
Save and close the file

Now you need to restart the machine, type "reboot" in terminal to restart via terminal.
Now you have successfully changed machine name.