# Filtering content of command with grep



## techinfozone (Dec 25, 2021)

I am trying to filter out a the output of ssh-keyscan. The goal of this is to filter the output so I can use it in my python code to identify hosts connected to my VPN. Normally I would use grep to filter, one of my greps is filtering properly, but the other is not. The first grep is working to get just the ed25519 ID, but not sure why I am getting the SSH-2.0... lines also. The command I ran along with the output is below:
user@host# ssh-keyscan 10.xx.xx.xx | grep ed25519 | grep -v "#"
  # 10.xx.xx.xx:22 SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3
  # 10.xx.xx.xx:22 SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3
  # 10.xx.xx.xx:22 SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3
  # 10.xx.xx.xx:22 SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3
  # 10.xx.xx.xx:22 SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3
  10.xx.xx.xx ssh-ed25519 <host key>

I need it to print only the ed25519 line. I have also tried AWK to filter, but still not getting the output I need.

Any idea how to filter only the ed25519 line?


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## cvaldes (Jan 4, 2022)

Well if you know the output is going to include "ssh-ed25519" you should grep on that.

Or pipe to that.

Or if you know it will be the last line of the output, pipe to the appropriate "tail" command.

Have you looked at the sed command?


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