Categories
Command Line Linux Posts

One Line IP Address Bash Command

ifconfig eth0 | sed -n '/^[A-Za-z0-9]/ {N;/dr:/{;s/.*dr://;s/ .*//;p;}}'

So you want to display just your IP address and not all the other stuff that comes with using the ifconfig command. Then use the above command.

It’s useful if you need your IP address in a script but you don’t want to set a static address for your machine, it outputs just the IP address on a single line as shown below:

Categories
Arch Linux Blog Command Line HowTo Linux Posts Ubuntu

HowTo: Remove Every Other Line in Text Files – Linux

Let’s say you’ve got a text file, of any size, big or small, and you want to remove every other line of that file, well here are a few commands in Linux that allow you to do this.

Example, you want to get from this:

1
2
3
4
5
6
7
8
9
10

To this:

1
3
5
7
9

The sed way:

 sed -n "p;N;" file.txt > newfile.txt

The awk way:

 awk 'NR%2 != 0' file.txt > newfile.txt

Here you can actually specify N lines, replace 2 in the above command and you’ll be able to take out every N’th number. As an example, here’s the above replaced with a 3 on the file:

1
2
4
5
7
8
10

Easy as pie, right?