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.

Answer 1

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 =)

Answer 2

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"

Answer 3

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

Answer 4

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`

Answer 5

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