grab_all_ssh_host_keys.sh

#!/bin/bash

#find all of the hosts listed in ~/.ssh/config
#apparently finding all the hosts ip/dns values is not trivial
grep -oPz 'Host .*\n  HostName .*' ~/.ssh/config |
sed -n 'N;s/Host \(.*\)\n  HostName \(.*\)/\1\n\2/p' |

while read hosts && read hostname; do
  echo "$hostname"

  if [[ "$hostname" == "%h"* ]]; then
    for host in $hosts; do
      echo "    ${hostname//'%h'/$host}"
    done
  else
    echo "    $hostname"
  fi |

  while read host; do
    echo -n "    "
    ssh-keygen -lf <(ssh-keyscan $host 2>/dev/null | awk '{print $2 " " $3 " " $1}')
  done
done