IP address oneliner

Command

The command to get a public IP from UNIX `ip addr` command:

ip -4 -o addr| \
 awk -F "( |/)" '$0 !~ " (10|127|172|192)\\." {print $7}'

The `ip` command options makes it to print only IPv4 addresses (`-4`) and output them in one line each (`-o`).

The `awk` app uses space and `/` as Field separators (`-F "( |/)`) and looks for lines without a substring containing one of 10, 127, 172, 192 numbers followed by a dot and preceded by space (`$0 !~ " (10|127|172|192)\\."`. It prints a seventh filed (`{print $7}`).

Example of ip command output

To better understand the pattern used in the `awk` below is an example of the output of the `ip` command.

1: lo    inet 127.0.0.1/8 scope host lo\       valid_lft forever preferred_lft forever
2: enp2s0f0np0    inet 56.112.121.59/32 metric 100 scope global dynamic enp2s0f0np0\       valid_lft 64241sec preferred_lft 64241sec
4: docker0    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0\       valid_lft forever preferred_lft forever