Awk/grep

Shell Programming and Scripting
1

Basically what I'm trying to do is pull the first three octets from the ipaddr out of ifconfig

ifconfig eth0 |awk -F" " '{ print $2 }'|grep addr: |awk -F":" '{ print $2 }'| awk -F"." '{print $1"."$2"."$3}'

keeps giving me

192.168.0
..

and I can not for the life of me get rid of the bottom half (the ..'s)

2

You could probably add one more pipeline:

... | head -1

But there may be a shorter way depending on your OS.

I.e. in Redhat:

$ hostname -I

Which OS are you using?

3 
root@bt:~# ifconfig eth0 |grep "inet addr" |awk -F":" '{print$2}'|awk -F"." '{print $1"."$2"."$3}'
192.168.0
root@bt:~# inet=$?
root@bt:~# echo "$inet"
0

my head is going to explode

---------- Post updated at 09:40 PM ---------- Previous update was at 09:39 PM ----------

Backtrack 5r3

Ubuntu

4

You're testing the result of the command with $?, not the output. If you want to store the output:

inet=$(...)

i.e.

$ inet=$(ip addr show eth0 | awk -F"[ /]" '/inet /{print $6}')
$ echo $inet
5

I'm trying to trim off that last octet so I can input the variable inet.* and run a nmap on specific ports.

---------- Post updated at 09:48 PM ---------- Previous update was at 09:46 PM ----------

Wait a tick, I see what you did. Thank you!

6 
# ip addr show eth0 | awk -F"[ /.]" '/inet /{print $6"."$7"."$8}'
10.10.44
7 
root@bt:~# inet=$(ifconfig eth0 |grep "inet addr" |awk -F":" '{print$2}'|awk -F"." '{print $1"."$2"."$3}')
root@bt:~# echo $inet
192.168.0

I've just started using awk. At the moment I only know how to grab fields. So the fancy things you're doing, I have no idea. This works though, thank's a bunch!

8

polishing your code snippet a bit:

inet=$(ifconfig eth0 | awk '/inet addr/ {gsub (/^.*:|\.[^.]*$/,"",$2);  print $2}')
echo $inet
10.1.1

... as awk can replace grep in certain instances...