I am new to the community and this is my first question, I hope I am doing it correctly.

My question: I am learning some networking and analysis and have a very long list of MAC addresses that I want to put in the same sentence using the command line but I do not know how.

Example: MAC addresses:


The output I need:

The mac address xx:xx:xx:xx:xx:xx:xx:xx is not found - but...
The mac address yy:yy:yy:yy:yy:yy:yy:yy is not found - but...
The mac address zz:zz:zz:zz:zz:zz:zz:zz is not found - but...

How can I achieve this?

I hope you have the time to help and excuse my ignorance, I am still learning and wouldn't ask if I didn't spend some time searching. I saw people using sed, awk, and perl but I understood nothing sense the whole linux world is new for me. Please provide me with some explanation with the commands so I learn how to do it myself for the next time.


2 Answers 2


Assuming your list is in a file called file with nothing else in it (as appears to be the case), you could use:

sed 's/.*/The mac address & is not found - but.../' file
  • s/old/new replace old with new
  • .* match any number of any characters on each line
  • & print what was matched earlier here

If you see the output you want, repeat the command (hit the up arrow to see and edit the previous command) adding redirection (>) to a new file at the end like this:

sed 's/.*/The mac address & is not found - but.../' file > newfile

Answer to first question:

sed 's/$/ is not found - but.../' FILENAME | sed 's/^/The mac address /'

This usage of sed just replaces fist string with the second one. $ means end of the line. ^ means beginning of the line.

Answer to second question:

sed 'N;s/\n/ /' FILENAME | sed 's/IP address:/This computer ip address is/' | sed 's/Computer name:/and is under the name/'

First sed merge every two lines. Remain seds replace old expression with new expression to build your new line.

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