How can I find active network interface from userland?

Question

I know that I can find which network interface is currently being used by parsing the output of:

# ifconfig

or

# route

But how can I get this information as a non-root user? Is there a way I can build such a

$ magic-command

whose ouput would be none lo or wlan0 or eth0 depending on the device used.. or even enp3s0f1 or wlp2s0 on exotic systems, with no admin rights?

Solution

Something like this?

ip addr | awk '/state UP/ {print $2}'
enp0s3:

This command was issued as a "regular" (non-root) user on:

uname -a
Linux centos 3.10.0-514.el7.x86_64 #1 SMP Tue Nov 22 16:42:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

If it is important to remove the trailing : from the interface name, use (for example):

ip addr | awk '/state UP/ {print $2}' | sed 's/.$//'
enp0s3

Comments

[iago-lito]

Perfect, cheers :)

[MaXi32]

Does this work in a virtual machine with bridged connection ? Tried this doesn't work.. it doesn't have the text state UP