Question

I am looking for a command line solution that would return me the primary (first) IP address of the localhost, other than 127.0.0.1

The solution should work at least for Linux (Debian and RedHat) and OS X 10.7+

I am aware that ifconfig is available on both but its output is not so consistent between these platforms.

Answer 1

Use grep to filter IP address from ifconfig:

ifconfig | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'

Or with sed:

ifconfig | sed -En 's/127.0.0.1//;s/.*inet (addr:)?(([0-9]*\.){3}[0-9]*).*/\2/p'

If you are only interested in certain interfaces, wlan0, eth0, etc. then:

ifconfig wlan0 | ...

You can alias the command in your .bashrc to create your own command called myip for instance.

alias myip="ifconfig | sed -En 's/127.0.0.1//;s/.*inet (addr:)?(([0-9]*\.){3}[0-9]*).*/\2/p'"

A much simpler way is hostname -I (hostname -i for older versions of hostname but see comments). However, this is on Linux only.