A One-Liner `sed` Command to Format SSH Config File

SED Command

sed -i -e '/^\s*#/!{/^\s*Host /!s/^\s*/\t/}' \

    -e '/^\s*Host /s/^\s*//' \

    ~/.ssh/config

Breakdown

• 
  

  Skip Commented Lines:

  
  
  
  
  
  • 
    /^\s*#/!{} : Ignores lines starting with #, possibly preceded by whitespace.
  
  
  
  
  
  




• Indent Non-Host and Non-Comment Lines:
  
  
  

  {/^\s*Host /!s/^\s*/\t/}

• 
  /^\s*Host /! : Matches lines that do not start with Host.


• 
  

  s/^\s*/\t/ : Replaces leading spaces or tabs with a single tab.

  
  
  
  
  
  • 
    Remove Leading Spaces from Host Lines:
    
  
  
  
  
  
  

  -e '/^\s*Host /s/^\s*//'

• 
  /^\s*Host / : Matches lines that start with Host.


• 
  s/^\s*// : Removes all leading spaces or tabs from those lines.

Example

Input:

Host myserver

HostName ssh.example.com

User myuser

 Port 22

 IdentityFile ~/.ssh/mykey



   Host another-server

    HostName another.example.com

   User anotheruser

Port 2022

IdentityFile ~/.ssh/anotherkey

Output:

Host myserver

    HostName ssh.example.com

    User myuser

    Port 22

    IdentityFile ~/.ssh/mykey



Host another-server

    HostName another.example.com

    User anotheruser

    Port 2022

    IdentityFile ~/.ssh/anotherkey

This formats the file in place (-i flag), ensuring consistent indentation and removing leading spaces.