update-known-hosts.sh

#! /bin/zsh

usage () {
  echo "usage: ${0:t} [-f known_hosts] host..."
}

KNOWN_HOSTS="$HOME/.ssh/known_hosts"

expanded_hosts() {
  case $(uname) in
    Darwin)
      echo -e "$1\t$(host $1 | awk '/address/ {print $4 "\t" $1}')"
      ;;
    *)
      echo -e "$1\t$(getent hosts $1)"
      ;;
  esac
}

while getopts ':hf:' opt; do
  case "$opt" in
    f)
      $KNOWN_HOSTS="$OPTARG"
      ;;
    h|?)
      usage
      exit
      ;;
  esac
done

if [[ $# -lt 1 ]]; then
  usage
  exit
fi

for arg in $*; do
  hosts="$(expanded_hosts $arg)"
  for h in ${=hosts}; do
    ssh-keygen -f "$KNOWN_HOSTS" -R $h 
  done

  ssh-keyscan -tdsa,rsa ${=hosts} >>"$KNOWN_HOSTS" 2>/dev/null
done

I use it with zsh parameter generation like:

 $ update-known-hosts.sh vdb-{001..016}

But you could do this on BSD:

$ update-known-hosts.sh $(jot -w vdb-%03d 16)

Or this on Linux: :-(

$ update-known-hosts.sh $(printf 'vdb-%03d\n' $(seq 16))