Read UNIX / Linux System IP Address In a Shell Script

by on January 16, 2006 · 32 comments· LAST UPDATED May 28, 2011

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Reading an IP address in shell script required many time. However, different Linux distribution stores IP address in different files. If you are looking to run script under different UNIX like OSes such as Solaris or FreeBSD then you need to use the ifconfig command. The ifconfig command is not just used to configure a network interface, but it can be use to obtained information such as network IP, netmask and much more.

Linux ifconfig Example

Type the following command:

ifconfig  | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}'

FreeBSD/OpenBSD ifconfig Example

Type the following command:

ifconfig  | grep -E 'inet.[0-9]' | grep -v '127.0.0.1' | awk '{ print $2}'

Sun / Oracle Solaris Unix Example:

Type the following command:

ifconfig -a | grep inet | grep -v '127.0.0.1' | awk '{ print $2}'

Note: use /sbin/ifconfig full path if you are the non-root user.

How Does It Works?

You are using the ifconfig command and sending its output to shell pipeline. A pipeline is a set of processes chained by their standard streams, so that the output of each process ("stdout") feeds directly as input ("stdin") of the next one.

  1. The ifconfig command list all network interfaces.
  2. From the output of ifconfig command, find out IPv4 IP address using the grep command (grep 'inet addr:').
  3. Next, you do not need loopback IP address (127.0.0.1) so again with the help of grep –v you invert the sense of matching, to select all non-matching lines.
  4. Finally, awk command is used to select an IP address. (awk '{print $2}')

See also: read-ip-address.bash script which reads/finds an IP address from different UNIX/Linux OSes.

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{ 32 comments… read them below or add one }

1 Anonymous January 17, 2006 at 9:43 pm

The process you listed would only give you the local address, if you are behind a firewall that uses NAT.

To get your public IP address try out the following bash script that I wrote a while ago:

#!/bin/bash

wget whatismyip.org
read T1 http://www.suramya.com

Reply

2 nixcraft January 18, 2006 at 12:42 am

Suramya,
Script is ok, but you can do that with one line command:

lynx –dump http://whatismyip.org/

Or better create a alias:

alias myip=’lynx –dump http://whatismyip.org/

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3 Anonymous January 18, 2006 at 12:48 am

True, This script is actually a portion of another script that sends out an email when my public IP changes. I just copied the portion that actually gets the IP and pasted it here.

That being said your version of the script is a lot cleaner. Mind if I ‘steal’ it for use in my scripts? ;)

Thanks,
Suramya

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4 nixcraft January 18, 2006 at 8:53 am

Mind if I ‘steal’ it for use in my scripts? ;)

Heh no problem, use it in your script :)

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5 Anonymous January 19, 2006 at 1:27 pm

@nixcraft. nice tip/hint :D I would like to see more shell scripting stuff here. keep it up good work

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6 Michael Gauthier June 15, 2006 at 3:24 am

If you don’t have lynx installed and want to use wget without messy temporary files, you can use:

wget -qO – http://whatismyip.org/

Reply

7 Clue December 18, 2007 at 12:52 am

Hi there,

I’m new to all this and I was wondering, how do those websites get our IP and is there not a shell script that can be written to find out your public IP depending on your private IP without having to use these external websites?

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8 TJB January 16, 2008 at 6:41 pm

Dude, you just saved me 15 minutes of relearning awk and the like just to pull out the IP addy. Double thanks!

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9 lex January 18, 2008 at 10:36 pm

@Clue
no. for as far as I know you’ll always need some external server to ‘see’ who you are.
But if someone knows another way to do this, the n please let me know.

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10 igor January 30, 2008 at 6:18 pm

if you use a different locale, consider this version for linux:

LC_ALL=C ifconfig | grep ‘inet addr:’| grep -v ‘127.0.0.1’ | cut -d: -f2 | awk ‘{ print $1}’

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11 Oscar February 1, 2008 at 9:42 pm

@the suggestion of using whatsmyip.

That is a great idea, but if you’re looking to find your ip address on a box that has no internet access then that would not work and the original script(s) should always work. If you’re on a private lan for example with no web access then you can’t see whatsmyip, or ipchicken, etc.

This quick how-to is not so much on how to find your external IP address, but more on the actual address your system has been assigned either DHCP, or statically.

Reply

12 Mohan February 27, 2008 at 2:33 pm

This should do the work

ifconfig eth0| awk ‘NR==2 {print $2}’| awk -F: ‘{print $2}’

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13 Alan Haggai Alavi November 26, 2008 at 2:16 pm

curl whatismyip.org does the same too. No need of extra parametres. :-)

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14 Paul Colby February 10, 2009 at 7:01 am

My current favourite:
ifconfig | sed -n -e 's/:127\.0\.0\.1 //g' -e 's/ *inet addr:\([0-9.]\+\).*/\1/gp'

;)

Reply

15 vio April 25, 2011 at 11:33 am

hostname -I

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16 Aaron Kushner May 13, 2009 at 9:37 pm

@mohan, you can have multiple separators and not have to rerun awk.
@paul, do you like yours because it has a sed abomination in it? Make it simple!

ifconfig eth0 | awk -F”[: ]+” ‘NR==2 {print $4}’

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17 Mika Marttila October 8, 2009 at 2:14 pm

Thanks! My virtual Ubuntu server is having problems keeping the same IP from DHCP. I need it to start bind my Django app for whole network so this tip came in handy.

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18 Marko Rauhamaa November 24, 2009 at 10:03 am

On linux:

hostname -i

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19 foo bar January 18, 2010 at 12:50 pm

OMFG, guys, please, you *do* realize anybody can hack into whatismyip.org and INSTANTLY gain access to your boxes ?!!!! And you’re not even using HTTPS – so any monkey in the middle can 0wn your boxes too !!!!
Are you dumb enough to run those lynx/curl scripts as root as well ???

NEVER EVER put this much trust into 3rd party systems, or you WILL get screwed !

it would be funny watching you after whatismyip.org returns `rm -rf /`

use ifconfig / ip show… and don’t be so freaking lazy

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20 Chris Browne June 8, 2011 at 9:24 am

Yeah, because lynx/curl execute the returned website. That’s how they work. Didn’t you know? They take what whatsmyip.org respond with, pass it into a system() call and it gets executed. Yup. And when you’re executing lynx as your user (which nobody suggested to do otherwise) rm -rf / is still able to wipe out your hard drive, because well… linux just doesn’t have a permissions system.

ifconfig on the other hand, an administrator’s tool which sends a lot of information about your network interfaces to your shell, potentially sending the result in an email if the script is run from cron; well, that’s just brilliant. So much more secure. I’d definitely recommend using ifconfig. Yup. Blast a load of intimate hardware details across SMTP, way more secure than fetching a HTML response from a web server that contains nothing but your IP address.

Seriously, though, if you’re gonna get angry at people for lax security practices at least have a clue what you’re talking about first.

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21 wag November 7, 2014 at 7:13 pm

The result from curl is not interpreted by curl itself, but might be by the shell script if not carefully written. Shell script injection is a common attack vector. If it happens, it’s already a huge security breach, even if the script doesn’t run as root.

“hostname -i” or even parsed ifconfig is much more secure, just don’t print the result if it contains sensitive data.

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22 neha kamra August 17, 2010 at 5:59 am

Hi

Can anyone send me the simple script with explanation to find the ip address…as i am new to this

thanx

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23 ulysses768 February 21, 2011 at 3:59 pm

This can be done exclusively in bash, if you’re interested in shaving a ms or two.
IP=`ifconfig`
IP=${IP#*inet addr:}
IP=${IP%% *}

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24 Danny Walker May 13, 2011 at 12:39 am

You can also do it in cygwin (you have to use Microsoft’s ipconfig command):

ipconfig | grep ‘IP Address’ | grep -v 0.0.0.0 | awk ‘{ print $15}’
($15 signifies the 15th word – the dots are words too!)

Therefore, to mimic cygwin’s default prompt, use:

export PS1=”\[\e]0;\w\a\]\n\[\e[32m\]\u@`ipconfig | grep ‘IP Address’ | grep -v 0.0.0.0 | awk ‘{ print $15}’` \[\e[33m\]\w\[\e[0m\]\n\$”

This work for me, but it’s a bit system specific. For example, if you have additional network interfaces, you may have to grep -v any others that might be returned.

Dan

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25 Gaveen June 13, 2011 at 11:59 am

Or you could run:

hostname -I

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26 Marissa March 3, 2012 at 5:54 am

bsr,
can any1 plzzzzz tell me wat’s the utility of this script (it gives the local address i know!! but y know my local address?!!!!!).
Thks.

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27 zlidka March 11, 2012 at 6:09 pm

run.
hostname
and learn your hostname if you dont know
and ping your hostname

Reply

28 neha September 25, 2012 at 5:33 am

hey i want to know: the code for running a shell script to connect a Setup Box(STB) through Jenkins integration tool by fetching its IP or MAC address. Please help..

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29 Dss April 16, 2013 at 4:11 pm

Update for Fedora v17 as the examples above won’t work.

ifconfig | grep ‘inet’| grep -v ‘127.0.0.1’ | cut -d: -f2 | awk ‘{ print $2}’

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30 Pavlichenko May 18, 2013 at 9:31 pm

Keep only one grep.

ifconfig wlan0 | grep -o -P ‘(?<=addr:)[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+\s'

——-
Ubuntu 13.04

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31 Devendra June 11, 2013 at 6:45 pm

ipconfig | grep “IPv4″ | awk ‘{print $14}’
working fine in cygwin

This is simple and self expainatory

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32 amin ghadesi November 9, 2014 at 10:06 pm

Hi, in CentOS el7 ….. this command changed to :
ifconfig | grep ‘inet ‘| grep -v ‘127.0.0.1’ | cut -d: -f2 | awk ‘{ print $2}’

Reply

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