How to display IP address of eth0 interface using a shell script?

For the sake of providing another option, you could use the ip addr command this way to get the IP address:

ip addr show eth0 | grep "inet\b" | awk '{print $2}' | cut -d/ -f1

• ip addr show eth0 shows information about eth0
• grep "inet\b" only shows the line that has the IPv4 address (if you wanted the IPv6 address, change it to "inet6\b")
• awk '{print $2}' prints on the second field, which has the ipaddress/mask, example 172.20.20.15/25
• cut -d/ -f1 only takes the IP address portion.

In a script:

#!/bin/bash
theIPaddress=$(ip addr show eth0 | grep "inet\b" | awk '{print $2}' | cut -d/ -f1)

Note: This answer is for older systems. If this does not work for you please consider other answers. This answer is not incorrect.

save this in a file and then run bash <filename>

#!/bin/bash
ifconfig eth0 | grep "inet addr"

being more accurate to get only number showing IP address:

#!/bin/bash
ifconfig eth0 | grep "inet addr" | cut -d ':' -f 2 | cut -d ' ' -f 1

Update: If this doesn't works for you, try the other answer

Update: For Ubuntu 18+, try: (don't forget to replace eth0 with interface you need the IP for. Thanks to @ignacio )

ifconfig eth0 | grep "inet " | awk '{print $2}'

Taken from https://stackoverflow.com/a/14910952/1695680

hostname -i

However that may return a local ip address (127.0.0.1), so you may have to use, and filter:

hostname -I

From hostname's manpages:

-i, --ip-address

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.

-I, --all-ip-addresses

Display all network addresses of the host. This option enumerates all configured addresses on all network inter‐faces. The loopback interface and IPv6 link-local addresses are omitted. Contrary to option -i, this option does not depend on name resolution. Do not make any assumptions about the order of the output.