Shell Programming and Scripting

#!/bin/bash
(( $# < 1 )) && {
    printf "usage: %s <file_name>\n" "${0##*/}"
    exit 1
}
 
_server_list=( server1 server2 )
 
_fn=$1
_cmd=/usr/bin/md5sum
 
function dossh
{
ssh "$1" "
   [ -f \"$_fn\" ] && 
      $_cmd $_fn ||
      printf \"error executing %s %s on %s\n\" \\
\"$_cmd\" \"$_fn\" \"$1\""
}
 
select s in "${_server_list[@]}" "All the above" "quit"; do
    if [[ -z "$s" ]]
    then
        echo "Option $REPLY is invalid - Please select a number from 1 to $(( ${#_server_list[@]} + 2))"
    else
      [[ "$s" = "quit" ]] && break
      if [[ "$s" == All* ]]
      then
            for s in "${_server_list[@]}"
            do
                dossh $s
            done
            continue
      fi
      dossh $s
    fi
done