It's useful to know what IP addresses have been assigned to your network Interfaces, and keep tabs on that. Reporting a host's IP address can be automated via a bash script, and that script can be scheduled to run periodically with cron or under systemd. Here are the essentials:
You should use ip (instead of ifconfig) as it's current, maintained, and perhaps most importantly for scripting purposes, it produces a consistent & parsable output. Following are a few similar approaches:
If you want the IPv4 address for your Ethernet interface eth0:
$ ip -4 -o addr show eth0 | awk '{print $4}'
192.168.1.166/24 Or, as a script:
#! /usr/bin/bash
INTFC=wlan0
MYIPV4=$(ip -4 -o addr show $INTFC | awk '{print $4}')
echo $MYIPV4Which will give the following output when run:
192.168.1.166/24
The output produced above is in CIDR notation. If CIDR notation isn't wanted, it can be stripped:
$ ip -4 -o addr show eth0 | awk '{print $4}' | cut -d "/" -f 1
192.168.1.166 Another option that IMHO is "most elegant" gets the IPv4 address for whatever interface is used to connect to the specified remote host (8.8.8.8 in this case). Courtesy of @gatoatigrado in this answer:
$ ip route get 8.8.8.8 | awk '{ print $NF; exit }'
192.168.1.166Or, as a script:
#! /usr/bin/bash
RHOST=8.8.8.8
MYIP=$(ip route get $RHOST | awk '{ print $NF; exit }')
echo $MYIPThis works perfectly well on a host with a single interface, but more advantageously will also work on hosts with multiple interfaces and/or route specifications.
ip would be my preferred approach, but it's certainly not the only way to skin this cat - nor the simplest. Here's another approach that uses hostname if you prefer something easier/more concise:
#! /usr/bin/bash
# simplest for single interface system:
hostname -I
# for multiple interface systems:
hostname --all-ip-addresses | awk '{print $1}' Or, if you want the IPv6 address:
#! /usr/bin/bash
hostname --all-ip-addresses | awk '{print $2}'