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Linux: Parse an IP Address

How do I parse my Linux servers IP address using a Bash shell?

You need to use the ifconfig or ip command to get ip address under Linux.

Parse an IP Address with ifconfig Command

Open a command-line terminal (select Applications > Accessories > Terminal), and then type the following commands:
# ifconfig eth0 | grep 'inet addr:'
Sample outputs:

          inet addr:192.168.2.100  Bcast:192.168.2.255  Mask:255.255.255.0

To get only an IP address, Bcast and Mask, use the egrep command as follows:
# ifconfig eth0 | egrep '([0-9]{1,3}\.){3}[0-9]{1,3}'
Sample outputs:

192.168.2.100
192.168.2.255
255.255.255.0

Parse an IP Address with ip Command

Use the ip command as follows:
# ip -f inet addr show eth0| grep 'inet'
Sample outputs:

inet 192.168.2.100/24 brd 192.168.2.255 scope global eth0

Just display an IP:
# ip -f inet addr show eth0 | awk -F'inet' '{ print $2}' | cut -d' ' -f21

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  • Scooter November 30, 2015, 8:58 pm

    On Ubuntu 14.04 LTS, your ‘ip addr’ example (ip -f inet addr show eth0 | awk -F’inet’ ‘{ print $2}’ | cut -d’ ‘ -f21) outputs nothing.

    First wanted to comment, parsing output of a command would generally be considered to not be “production quality code”. This applies to my working example also :-)

    Try:
    ip -f inet addr show eth0 | awk '/inet /{ print $2}'|cut -d'/' -f1

    In general, be VERY careful about using -f with whitespace… different OS distros may handle this differently (are 4 spaces considered one block of whitespace? Or 4? What about a single tab?). awk is better about supporting different “whitespace” scenarios, than simple ‘cut’ is.

    Anyone could clean up my code further (or point out edge cases where it fails, as I would if your iface IP address weren’t a typical /24)

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