Assigning IP address to environment variable

Question

How can I assign the IP address of eth0 to an environment variable, say $ip, as easily as possible?

Update: Distro is Ubuntu Server 12.04 LTS.

score 7 · Answer 1 · answered Dec 18 '12 at 23:59

7

A shorter (and I find more neat) way is hostname -i. No more hassle with ipconfig, ip, sed, awk and such.

answered Dec 18 '12 at 23:59

ott--

856

3

+1, although note that my manpage says: -i: Display the network address(es) of the host name. Note that this works only if the host name can be resolved. Avoid using this option; use hostname --all-ip-addresses instead. – ire_and_curses Dec 19 '12 at 00:12
Unfortunately this only gives me 127.0.1.1. This may be because machine is running behind NAT in VBox. Still a useful answer. Will upvote. – user204863 Dec 19 '12 at 08:35

rsaw · Answer 2 · 2012-12-19T01:23:24.050

Using ip address show is the way to go. Especially on any modern linux system where the interface you're querying could have multiple addresses that ifconfig wouldn't know about.

$ ip a s eth0 | awk '/inet / {print$2}'
10.13.211.83/24
192.168.17.21/16

And of course if you don't want the netmask, just pipe that to any number of things, e.g.:

cut -d/ -f1

Note: On the same system, ifconfig shows:

$ ifconfig em1 | awk '/inet / {print $2}'
10.13.211.83

Gilles Quénot · Answer 3 · 2012-12-19T15:42:47.120

1

Try doing this :

ip=$(
    ifconfig eth0 |
    perl -ne 'print $1 if /inet\s.*?(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\b/'
)
echo "$ip"

edited Dec 19 '12 at 15:42

answered Dec 18 '12 at 23:08

Gilles Quénot

33,867

Thank you very much, this was what I was looking for! :) – user204863 Dec 18 '12 at 23:10
2

If you think that the answer is useful, you can 'upvote' it. You can 'accept' the reply too by clicking the outline of the checkmark (will be green), this way, people searching stackexchange website will known that the question is well answered. That's how stackechange websites works, thanks ;) – Gilles Quénot Dec 18 '12 at 23:12
This only works if your ifconfig answers in English. For other languages, you need to change /inet\s+ad+r to what your version says – laurent Dec 19 '12 at 00:39
This didn't work for me at all. Why make it so complicated? – rsaw Dec 19 '12 at 01:29
@laurent, language don't change anything. Tested both in LANG=C and LANG=fr_FR.UTF-8. Moreover, tested OK on ubuntu 12.10 – Gilles Quénot Dec 19 '12 at 15:35
The output of ifconfig is different from language to language and the filter doesn't work. For example instead of inet addr: in English (inet adr: I suppose in French), in my machine in pt_BR, I have inet end.: and the output using your solution is blank. It's only a matter of adapting the filter for each language. – laurent Dec 19 '12 at 15:41
New one should work on many use cases – Gilles Quénot Dec 19 '12 at 15:43
Ok, it worked with the new one. – laurent Dec 19 '12 at 15:51
You really should consider using ip instead of ifconfig. ifconfig is deprecated and will most likely be replaced by ip in future releases of your distro. – jsbillings Dec 19 '12 at 16:12

score 1 · Answer 4 · answered Dec 19 '12 at 00:32

1

Not answer to your exact problem as you want the IP assigned to a defined interface but I thought it could be usefull to have listed here for future info the way to have your external IP (even if behind a NAT):

ip=`wget -qO- ipecho.net/plain`

answered Dec 19 '12 at 00:32

laurent

655
4
7

score 1 · Answer 5 · answered Jul 24 '13 at 09:48

Check out also:

ifconfig eth0 | awk '/inet /{print $2}' | cut -f2 -d':'

that will work even in Solaris and HP-UX (use appropriate net dev instead of eth0).

As for hostname -i command, try hostname -I if you have one configured interface (except loopback).

Gilles Quénot · Answer 6 · 2012-12-19T19:12:21.700

0

As you can see, hostname -i can show 127.0.0.1 (no NAT here (archlinux)), this is not what we want.

So I propose :

dev=eth0
ip=$(
    ip a s dev $dev |
        awk '/inet /{gsub("/.*", "");print $2}'
)
echo "$ip"

Or if you have -P switch for grep :

ip a s dev eth0 | grep -oP 'inet\s+\K[^/]+'

I guess that's the shortest solution =)

edited Dec 19 '12 at 19:12

answered Dec 19 '12 at 19:03

Gilles Quénot

33,867

score -1 · Answer 7 · answered Jul 24 '13 at 04:11

-1

Yon can also try this,

IP=`wget -q -O- http://checkip.dyndns.org/index.html | grep 'IP'| html2text | cut -c 21-36`

answered Jul 24 '13 at 04:11

n_techo

1

1

Given that html2text is not a POSIX tool, could you specify from where we could take it? – manatwork Jul 24 '13 at 12:13

Assigning IP address to environment variable

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