[SOLVED] using grep to find the network interface name.

jamiebbbb · 03-23-2017, 04:57 AM

Hi

I hope someone can help me.I have a script that runs this command
iwconfig 2>&1 | grep 802.11 | grep' + interface'
The interface is a variable

This part of the script works

iwconfig 2>&1 | grep 802.11

the output is
wlan0 IEEE 802.11 ESSID:"Virus"

this command grep' + interface
it is meant to when it receives it variable input - output the individual interfaces.
wlan0
eth0
It doesn't
I have experimented with various grep commands
the only way i have been able to do the task successfully
is to grep iwconfig to a file called net.txt
then
awk '/wlan0/ {print $1}' net.txt
is there a way that i can do it just using the Grep command ??

Thanks
jamie

Turbocapitalist · 03-23-2017, 05:24 AM

Welcome.

You'll need to look at the different styles of quoting. The single quotes ' ' mean to use everything between them as a a literal. The double quotes " " mean to interpret what's between them through the shell first. The latter is what you want since it will allow you to put a variable in there first. With awk you can assign environment variables to awk variables using -v

Code:

interface="wlan0"

iwconfig 2>&1 | grep "$interface"

iwconfig 2>&1 | awk -v i=$interface '$0 ~ i { print $1 }'

Compare:

Code:

interface="wlan0"
echo '$interface'
echo "$interface"

jamiebbbb · 03-23-2017, 06:52 AM

extremely grateful - thank you for sharing your knowledge - much appreciated