How to check command line for a word

[DeadBeet]

I'm building a script for my place of employment. The next step in it is checking what the user input was. Determining if they added a part in there or not.

The script prompts for a hostname. Hostnames are localhost.localdomain. Now, I want the script to check to see if they put localdomain and if they did, not to add the domain to the /etc/sysconfig/network, but just what they entered.

So say the user inputs:

Please enter hostname: Localhost
read HOSTNAME;

sed -i 's/localhost.localdomain/$HOSTNAME.localdomain/g' /etc/sysconfig/network

Please enter hostname: localhost.localdomain
read HOSTNAME;

sed -i 's/localhost.localdomain/$HOSTNAME/g' /etc/sysconfig/network

How do I have the script check $HOSTNAME to see if they put in .localdomain or not?

Let me know if I need to explain it better..

Thanks

[Franklin52]

Use double quotes, single quotes prevent the shell to expand variables:

sed -i "s/localhost.localdomain/$HOSTNAME.localdomain/g" /etc/sysconfig/network

[DeadBeet]

But what if they added .localdomain in their input? I don't want to put it in there again. Is that what " " do?

[Franklin52]

Post some lines of etc/sysconfig/network and an example of the desired output.

[DeadBeet]

That's almost irrelevant. I'm trying to have the script check the command line for a word.