The Problem

Ever needed to grab your IP address from a bash script? Here’s a quick one-liner that’s saved me countless times!

The Solution

If your ethernet interface is eth0:

$ IPADDR=$(ifconfig eth0|grep inet|head -1|sed 's/\:/ /'|awk '{print $2}')
$ echo $IPADDR
172.17.0.3

How It Works

Let’s break this down step by step:

1. ifconfig eth0 - Gets interface information for eth0
2. grep inet - Filters for lines containing “inet”
3. head -1 - Takes just the first match
4. sed 's/\:/ /' - Replaces colons with spaces for easier parsing
5. awk '{print $2}' - Grabs the second field (which is our IP)

Modern Alternative

If you’re on a newer system, you might prefer using ip instead of the older ifconfig:

$ IPADDR=$(ip route get 1 | awk '{print $NF;exit}')
$ echo $IPADDR
172.17.0.3

This approach is more reliable because it gets the IP of the interface that would be used to reach the internet.

Pro Tips

• Always test your scripts in your specific environment - network interface names can vary!
• For production scripts, add error checking to make sure the interface exists
• Consider what happens if the interface is down or doesn’t have an IP

Appendix: References

• General Bash Guide: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html

Sometimes the simplest solutions are the best ones! 🚀