I need to append a line at the bottom of /etc/hosts file to include the current ip address for my pc.

I found the following command that obtains the ip address, but it echo's it to the display and I need to use it as a variable in a shell script in conjunction with the cat command.

Here is the command that echo's the ip address to the display: ifconfig | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}'

I am using CentOS 6.5

Thanks

Will echo Hello to stdout.
Will append Hello to file.txt

You might also want to have a bit more of a look at the awk command as on its own it would be able to complete all the steps where you use grep and cut

this will append in /etc/hosts an entry with ip address and hostname, which is probabbly what you want anyway.

regards awk I have seen it described as 'glorified grep'

Building on previous example


Makes little difference here, but consider large complex scripts running on a loaded server and limiting the no. of pipes (and sub shells ) can make all the difference



A great guide for scripting

http://mywiki.wooledge.org/BashGuide/

It highlights many bad habits you can pickup from the net..

It also depends if you have multiple interfaces. Do you want the internet routable IP? And whether you want the public or private IP of your system.

If you want the public IP.

If you want the IP of the interface that has a default route set up for internet then you'd want something like the following command.

I blogged about it here on LQ.

I tried both the awk & ifconfig examples below and they both give me what I want except the have a leading "addr:" at the beginning of the output line. Is there anyway to clean that up?

awk -v host=$(hostname) '/inet / && !/127\.0\.0\.1/ {printf("%s %s\n",$2,host)}' < <(/sbin/ifconfig) >> /etc/hosts
ifconfig |grep "inet " | grep -v "127\.0\.0\.1" |awk -v host=$(hostname) '{printf("%s %s\n",$2,host)}' >> /etc/hosts

You should not have any leading "addr" ulness that's an IP address:

If you have more then one interface configured (or alias) you get multiple lines with different IP but same hostname ... you just need to redirect output to /etc/hosts instead of having it shown on standard output.
If you are still getting text in front of the IP address I suspect that your distro is writing something like "inet:192.168.1.4"
so you might haveto work a bit hardet to get the result you want.

Why are you doing this ? do you have a machine that is configuring IP via DHCP and you want to add itself to hosts ?
If so you might want to have an IP reserved on DHCP server so that you get the same one each time and you can do without this thing.

Alternatively you can have the post ip up hook scripts fix the address in hosts for you. This depends on the dhcp client you are using. Look at your client's man page for more details on how you might go about it.

Actually the addr: string comes from the output of ifconfig. Anyway, an alternative method is the ip command. Here is an example:

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Thanks for the help Colucix! That worked perfectly.

Again it depends on what you want. If you want the default interface that has internet access you'll want to account for that.

That is the exact command I used in my first post but I added the $HOSTNAME env variable and I'm appending it to /etc/hosts. You should look up the man pages and understand the commands that are being handed to you in this thread. Attempting to filter out the loopback (lo) interface is not very good and you should be using a command similar to what I've given you.

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