Linux ifdata Command: See Network Interface Info Without Parsing ifconfig Output

Posted on in Categories Command Line Hacks, Debian Linux last updated December 12, 2012

Reading an IP address in a shell script requires many time and various Linux distributions stores IP address in different text files. So most of us end up writing shell pipes/scripts to get the information using ifconfig | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}' syntax. There is an alternative to ifconfig+shell pipe hack – ifdata command. It is a little know tool that can be used to check for the existence of a network interface and find out info about your interface such as IP, netmask, MTU and much more. No need to write shell pipes and fetch information via ifconfig or ip command. This command is designed to be easily used by a shell script.

Linux / Unix ifdata Command - Find Info About Network Interface
Fig.01: Linux / Unix ifdata Command – Find Info About Network Interface

How do I install ifdata command?

Simply type the following command at shell prompt:
$ sudo apt-get install moreutils
OR
$ sudo yum install moreutils

Examples

Find out if the interface ppp0 exists or not, enter:

ifdata -e ppp0 && echo "Found" || echo "Not found"

OR

ifdata -e ppp0 && echo "Found" || { echo "Not found, starting pppd..."; pppd call barISP; }

Show eth0 configuration:
$ ifdata -p eth0
Sample outputs:

192.168.1.5 255.255.255.0 192.168.1.255 1500

Get the IPv4 address of the interface, enter:

#!/bin/bash
# my firewall script
# Get ip for eth0
_ip=$(ifdata -pa eth0)
_ipt=/sbin/iptables
 
## do something on $_ip ##
echo "Setting firewall for eth0 and ${_ip}..."

The complete summary of all options supported by ifdata command:

Usage: ifdata [options] iface
     -e   Reports interface existence via return code
     -p   Print out the whole config of iface
    -pe   Print out yes or no according to existence
    -pa   Print out the address
    -pn   Print netmask
    -pN   Print network address
    -pb   Print broadcast
    -pm   Print mtu
    -ph   Print out the hardware address
    -pf   Print flags
    -si   Print all statistics on input
   -sip   Print # of in packets
   -sib   Print # of in bytes
   -sie   Print # of in errors
   -sid   Print # of in drops
   -sif   Print # of in fifo overruns
   -sic   Print # of in compress
   -sim   Print # of in multicast
    -so   Print all statistics on output
   -sop   Print # of out packets
   -sob   Print # of out bytes
   -soe   Print # of out errors
   -sod   Print # of out drops
   -sof   Print # of out fifo overruns
   -sox   Print # of out collisions
   -soc   Print # of out carrier loss
   -som   Print # of out multicast
  -bips   Print # of incoming bytes per second
  -bops   Print # of outgoing bytes per second

I hope you will use this tiny too for the good.

Related Internet links

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

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12 comment

  1. Here is an alternative function using /sbin/ip that gives you useful information . I call it ‘ship’ for SHow IP :

    ship ()
    {
    [ $1 ] && DEVLIST=$1 || DEVLIST=$(ip addr show | grep ^[0-9] | cut -d: -f 2);
    for DEV in $DEVLIST;
    do
    IP_ADDR=$(/sbin/ip addr show dev ${DEV} | grep ${DEV}$ | awk ‘{ print $2 }’ | cut -d/ -f 1);
    RC=$?;
    [ -z $IP_ADDR ] || echo “${DEV}: ${IP_ADDR}”;
    done
    }

    [server:~] # ship
    lo: 127.0.0.1
    bond0: 10.196.76.17
    [server:~] #

  2. Wow, this is very helpful! Yes ifconfig can be a mess sometimes- I am always appreciative of smarter people who help dumb people like me do things quicker and better! Thanks,

  3. Nice tutorial buddy! ifconfig can be a bit clumsy sometimes and it’s nice to know there’s an alternative :)

  4. I had to install moreutils on Debian sid, because ifdata does not appear to exist as a separate package in apt.

  5. Alternatively, you can use the ‘ip’ command. Its output isn’t quite as clean as ifdata, but it will always be on any modern system:

    root@host:~# ip -o -4 addr show eth0
    2: eth0 inet 10.154.26.36/23 brd 10.154.27.255 scope global eth0
    root@host:~#

    Depending on the scripting you are doing, parsing the above with awk or cut is probably preferable to an additional dependency.

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