for-each

for-each

is a simple command line tool to execute a command or a list of commands on a list of servers. You can provide the list of servers either as a file or via stdin.
The list must be formatted as a table, with the server name in the first column and the server IP in the second column.
The tool does not parse the rest of the table, which can contain any data convenient for filtering the list.

The tool utilizes the system's SSH utility and does not request passwords from the tty. Therefore, key-based authentication is required for the tool (as well as membership in the 'wheel' group for passwordless sudo, if needed).

The tool automatically creates log files for each server in the ./logs folder unless the --no-logs option is specified.
Each log file created by the tool contains all executed commands, along with timestamps and the output for each command.

Examples:

• Execute cat /etc/hostname on a list of servers, piping the list from servers from stdin:

  cat <<END | for-each cat /etc/hostname  
  server1 192.168.0.10  
  server2 192.168.0.11   
  END  
  

• Execute cat /etc/hostname on a list of servers, specifying the list of servers as a file:

  cat > servers.txt <<END  
  server1 192.168.0.10 =gpu  
  server2 192.168.0.11 =worker  
  server3 192.168.0.12 =gpu  
  END  
  
  for-each -f servers.txt cat /etc/hostname 
  

• Execute cat /etc/hostname on gpu servers only:

  cat > servers.txt <<END  
  server1 192.168.0.10 =gpu  
  server2 192.168.0.11 =worker  
  server3 192.168.0.12 =gpu  
  END  
  
  grep =gpu servers.txt | for-each cat /etc/hostname
  

• Execute a list of commands on a list of servers.
  I intentionally don't call it a script, because the tool does not really run it as a remote script.
  Instead it executes the commands from the list via ssh one by one.
  This way it does not create any files on the remote servers.

  cat > commands.txt <<END  
  apt update  
  apt install -y   
  END
  
  cat <<END | for-each -s commands.txt  
  server1 192.168.0.10  
  server2 192.168.0.11   
  END