Getting Root Domain for String in Shell9 months ago

I was looking for a quick way to determine the root domain of a host passed to me in a shell script, this is what i came up with:

      awk -F . '{print $(NF-1)"."$NF}'

Examples

njp-mbp: ~> echo "domain.com" | awk -F . '{print $(NF-1)"\."$NF}'    
      domain.com
njp-mbp: ~> echo "sub.domain.com" | awk -F . '{print $(NF-1)"\."$NF}'
      domain.com
njp-mbp: ~> echo "longer.sub.domain.com" | awk -F . '{print $(NF-1)"\."$NF}'
      domain.com
njp-mbp: ~> echo "longer-domain.com" | awk -F . '{print $(NF-1)"\."$NF}'    
      longer-domain.com