The name says it all. Please share your best command line scripts and explain their use.
alias IPADDRESSES="ip addr|grep 192;curl -s http://checkip.dyndns.org/ | grep -o '[[:digit:].]\+'"
This command sets up an alias command to display your internal ip address(es) and display your external ip address using dyndns.
You only need to supplement the 192 with the first octet of you internal network subnet.