mjhjmtu

How to capture the first IP address that comes from ifconfig command?

ifconfig -a
enw178032: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
 inet 100.14.22.12 netmask 255.255.0.0 broadcast 100.14.255.255
 inet6 fe80::250:56ff:fe9c:158a prefixlen 64 scopeid 0x20<link>
 ether 00:10:56:9c:65:8a txqueuelen 1000 (Ethernet)
 RX packets 26846250 bytes 12068811576 (11.2 GiB)
 RX errors 0 dropped 58671 overruns 0 frame 0
 TX packets 3368855 bytes 1139160934 (1.0 GiB)
 TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Expected result:

IP=100.14.22.12

It is better avoid using ifconfig for getting an IP address in a scriptas it is deprecated in some distributions (e.g. CentOS and others, do not install it by default anymore).

In others systems, the output of ifconfig varies according to the release of the distribution (e.g. the output/spacing/fields of ifconfig differs from Debian 8 to Debian 9, for instance).

For getting the IP address with ip, in a similar way you are asking:

ip addr | awk ' !/127.0.0.1/ && /inet/ gsub(//.*/, "", $2); print "IP="$2 '

Or better yet:

$ ip -o -4 address show | awk ' NR==2 gsub(//.*/, "", $4); print $4 '
192.168.1.249

Or, as you ask "IP="

#!/bin/bash
echo -n "IP="
ip -o -4 address show | awk ' NR==2 gsub(//.*/, "", $4); print $4 '

Adapting shamelessly the idea from @Roman

$ ip -o -4 address show | awk ' NR==2 gsub(//.*/, "", $4); print "IP="$4 ' 
IP=192.168.1.249

Normal output:

 $ ip -o -4 address show 
1: lo inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever
2: eth0 inet 192.168.1.249/24 brd 192.168.1.255 scope global eth0 valid_lft forever preferred_lft forever

From man ip:

-o, -oneline

output each record on a single line, replacing line feeds with
the '' character. This is convenient when you want to count
records with wc(1) or to grep(1) the output.

See one example of why ifconfig is not advised: BBB: `bbb-conf --check` showing IP addresses as `inet` - ifconfig woes

For understanding why ifconfig is on the way out, see Difference between 'ifconfig' and 'ip' commands

ifconfig is from net-tools, which hasn't been able to fully keep up
with the Linux network stack for a long time. It also still uses ioctl
for network configuration, which is an ugly and less powerful way of
interacting with the kernel.

Around 2005 a new mechanism for controlling the network stack was
introduced - netlink sockets.

To configure the network interface iproute2 makes use of that
full-duplex netlink socket mechanism, while ifconfig relies on an
ioctl system call.

Awk solution:

ifconfig -a | awk 'NR==2 sub(/^[^0-9]*/, "", $2); printf "IP=%sn", $2; exit '

Sample output:

IP=10.0.2.15

ip addr | grep -v 127.0.0.1 | grep 'inet ' | 
awk 'print $2' | awk -F "/" 'print "IP="$1'