How to Find out the IP address assigned to eth0 and display IP only

Posted on in Categories , last updated December 5, 2007

Q. I need to get the IP address assigned to eth0 Linux interface. How do I find out IP address only? I don’t want other information displayed by Linux ifconfig command.

A. For shell script or may be for other cause you may need the IP address only. You can use ifconfig command with grep and other filters.

Default output of /sbin/ifconfig command is all interfaces:
$ /sbin/ifconfigOutput:

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:69527 errors:0 dropped:0 overruns:0 frame:0
          TX packets:69527 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:41559546 (39.6 MiB)  TX bytes:41559546 (39.6 MiB)

eth0      Link encap:Ethernet  HWaddr 00:17:9A:0A:F6:44
          inet addr:192.168.2.1  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::217:9aff:fe0a:f644/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:227614 errors:0 dropped:0 overruns:0 frame:0
          TX packets:60421 errors:0 dropped:0 overruns:0 carrier:0
          collisions:272 txqueuelen:1000
          RX bytes:69661583 (66.4 MiB)  TX bytes:10361043 (9.8 MiB)
          Interrupt:17

ra0       Link encap:Ethernet  HWaddr 00:50:56:C0:00:01
          inet addr:192.168.1.2  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fec0:1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1024 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1320 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

Now you just select eth0 as follows:
$ /sbin/ifconfig eth0

Now you just wanted the IP address, use grep to get the IP:
$ /sbin/ifconfig eth0| grep 'inet addr:'Output:

inet addr:192.168.2.1  Bcast:192.168.2.255  Mask:255.255.255.0

To get IP address from use cut command:
$ /sbin/ifconfig eth0 | grep 'inet addr:' | cut -d: -f2Output:

192.168.2.1  Bcast

Finally remove Bcast with awk
$ /sbin/ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'
Output:

192.168.2.1

See how to read UNIX/Linux system IP address in a shell script

52 comment

  1. another option is to use “ip” command:
    ip addr list eth0 |grep inet |cut -d' ' -f6|cut -d/ -f1
    which prints both ipv4 and ipv6 addresses, ipv4 addr can be printed using tighter grep expression:
    IPv4:
    ip addr list eth0 |grep "inet " |cut -d' ' -f6|cut -d/ -f1
    IPv6:
    ip addr list eth0 |grep "inet6 " |cut -d' ' -f6|cut -d/ -f1

    1. thank you, exactly what I’m looking for (now in my bash profile):
      alias ip=”ifconfig en0 | grep ‘inet ‘ | cut -d ‘ ‘ -f 2″

      1. I wouldn’t know your system but ip is a command that distributes with several linux distributions as /sbin/ip
        Alternatively you might try this:
        alias ip_addr="ifconfig en0 | grep 'inet ' | cut -d ' ' -f 2"

  2. Bob wins. The rest of you should go self-flagellate for being moronic punks.

    Rules of thumb for efficient text processing:

    a. Avoid the need to do so. If there’s a command that outputs exactly what you need, use it. (For example, in our case here, using ‘hostname -i’ instead of stupidly dicking around with ifconfig, cut, grep, sed, and awk). Use some common sense, for Christ’s sake. Think maybe nobody else ever needed to include their IP address in a command? Before you go monkey-spanking around with awk or perl, see if there’s an appropriate command.

    b. if there’s a shell built-in that can do it, use that (your shell is already loaded into memory, and there is overhead in making a call to an external). For example, if you can parse a line effectively using the shell’s string substitution features, then do so. Don’t be a dumb-ass and waste your RAM and CPU. Read your shell’s man page.

    b. If the shell can’t do it, use the simplest alternative that can. If cut or tr will work, use that. If not, use sed. If not use awk.

    c. The biggest sin of all, an abomination of a command that pipes together more than one of the above, awking the output of grep, for example.

    1. While I agree with your principles, Bob is actually wrong – hostname does a lookup into the /etc/hosts file and may or may not give you the IP address of eth0. It depends on what you have in your hosts file. For example, I have a machine where “hostname -i” returns 127.0.0.1, simply because there was no name associated with the IP address of eth0 (192.168.0.16).
      Grep/awk/sed pipes are costly in regards to system resources as you outlined, but sometimes you have to use them. What would be better is if there were a command that simply went “get-ip-address eth0” and returned the IP, but I have not found one as of yet.

    2. John,

      Wow, you’re rather fun, aren’t you? Let’s dismiss beginners and overlook the intrinsic value of getting a look at how cut, grep and the others work for those folk [incl. me] and let’s just show how you’ve happily traded ‘my linux is better than yours’ for people skills.

    3. Actually, hostname -i is a bad choice because you can’t be sure it will return the ip of eth0. It could return 127.0.0.1, or whatever is configured in /etc/hosts. Also hostname -I is a bad choice because on a multi-NIC system it will return more than one ip address.

      Another option is:
      ETH0_IP=$(ifconfig eth0 | awk ‘/inet / {print $2}’);

      I like the above solution because if an ip is not set then awk will return nothing, this is good because you can then do error checking, such as:

      if [[ -z ${ETH0_IP+x} ]]; then echo “eth0 ip not set.”; fi

      1. Here is an example of error checking in action:

        if [[ -z ${HTTP_IP_ADDRESS+x} ]]; then
        HTTP_IP_ADDRESS=$(ifconfig br-ctlplane | awk '/inet / {print $2}');
        fi

        if [[ -z ${HTTP_IP_ADDRESS} ]]; then
        echo "Environment variable HTTP_IP_ADDRESS is not set, aborting.";
        exit 1;
        fi

  3. Recommend “ip addr” for those with many VLAN IPs

    “ip” is in the “iproute” package, “apt-get install iproute”

  4. I am not agree with John,
    with comments like this “Don’t be a dumb-ass and waste your RAM and CPU”.
    It looks like you living in 19 century, you better group old man, this days RAM is cheap and CPU is big, and don`t jump on people who like to experiment with thinks.

    Who like to experiment try this:
    hostname -I | cut -d: -f2 | awk ‘{ print $1}’
    or this
    hostname -I | cut -d: -f2 | awk ‘{ print $2}’

  5. very useful tips,
    In my case, I want to list all my server IPs assigned to eth0, the ifconfig results something like

    ###
    eth0 Link encap:Ethernet HWaddr 00:16:3E:D8:2B:BF
    inet addr:127.0.0.1 Bcast:192.168.0.127 Mask:255.255.255.128
    inet6 addr: fe80::216:3eff:fed8:2bbf/64 Scope:Link
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:4311554 errors:0 dropped:0 overruns:0 frame:0
    TX packets:3027306 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:1000
    RX bytes:944036536 (900.3 MiB) TX bytes:6041030741 (5.6 GiB)
    Interrupt:24

    eth0:0 Link encap:Ethernet HWaddr 00:16:3E:D8:2B:BF
    inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    Interrupt:24

    eth0:1 Link encap:Ethernet HWaddr 00:16:3E:D8:2B:BF
    inet addr:192.168.0.3 Bcast:192.168.0.255 Mask:255.255.255.0
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    Interrupt:24
    ###

    currently, for single IP, I can use this command
    SERVERIP=`grep IPADDR /etc/sysconfig/network-scripts/ifcfg-eth0 | awk -F= ‘{print $2}’`
    echo $SERVERIP

    How to list all of my IPs?
    Please reply to my email :)
    Many thanks

  6. I prefer doing it this way…

    ifconfig eth0 | grep ‘inet addr:’ | cut -d”:” -f2 | cut -d” ” -f1

    If hostname -i or hostname -I don’t give me what I want.

  7. I thought I’d post since I didn’t see this answer:

    cat /sys/class/net/eth0/address

    For my setup, hostname -i only gives me the loopback address (127.0.0.1).

  8. I try to avoid external programs for simple string task:

    ipaddr=$(/sbin/ifconfig eth0) ; ipaddr=${ipaddr/*inet addr:/} ipaddr=${ipaddr/ */}
    echo "$ipaddr"
    
  9. Of course “dnsdomainname -i” really does the same thing but the discussion is about the details and understanding of how to get the proper value by chopping again and again…!

  10. I hardcode my IP address in /etc/sysconfig/network-scripts/ifcfg-eth3; yet when I list it (ifconfig -a) I do not see my IP address that I hardcoded? please help.

  11. Actually, hostname does not work. I am running a LAMP server so hostname gives 127.0.0.0 . I have eth0 connected to a router and ONLY ifconfig gives me the correct IP. Bob is an idiot.

  12. Correction:
    John is an idiot for saying:

    “Bob wins. The rest of you should go self-flagellate for being moronic punks.”

    Sorry, Bob.

  13. You can do this easier and better:

    ip=$(echo “$(hostname -I) | grep -o ‘^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}’)

    This don’t care what interface you are using.

  14. I am still trying to learn how to use grep and do not really have firm grasp of ‘regex’ can someone recommend a book to start out with?

  15. #!/bin/bash
    wifiip=$(ip addr | grep inet | grep wlan0 | awk -F" " '{print $2}'| sed -e 's/\/.*$//')
    
    
    eth0ip=$(ip addr | grep inet | grep eth0 | awk -F" " '{print $2}' | sed -e 's/\/.*$//')
    
    
    # report findings, only returning devices with IPs
    
    if [ "$eth0ip" -eq " " ]  
    then
    echo "$wifiip" | grep [0-9]$ > /home/pi/attendance/ip.txt
    
    else
    echo "$eth0ip" | grep [0-9]$ > /home/pi/attendance/ip.txt
    
    fi

    i am trying to place working interface ip-address into a text file but its throwing error on executing this script

    ip.sh: 14: [: unexpected operator

  16. Cuts can be funky, here is one with only grep and awk:

    ifconfig eth0 | grep ‘inet addr:’ | awk ‘{print $2}’ | awk -F’:’ ‘{print$2}’

  17. ifconfig eth0 | grep ‘inet addr’ | awk ‘{print $2}’ | cut -d: -f2

    or for german users (german system language):
    ifconfig eth0 | grep ‘inet Adr’ | awk ‘{print $2}’ | cut -d: -f2

  18. Skuutter is the best option for me I’m using the ipv4 version he submitted

    ip addr list eth0 |grep “inet ” |cut -d’ ‘ -f6|cut -d/ -f1

    and it just works great for getting and inserting the ip address into a variable for the script I’m running.
    As to the complaints about complex commands if the n00bs need to find their ip addresses then just right click on the NetworkManager and chose connection details…Doooh

  19. I can’t say I fully understand why/how, but “bulb”‘s answer works for me on RHEL7:

    ipaddr=$(/sbin/ifconfig eth0) ; ipaddr=${ipaddr/*inet addr:/} ipaddr=${ipaddr/ */}
    echo $ipaddr

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