Clean ssh known_hosts files for a specified user

ssh_key_clean.sh

#!/bin/bash

# ssh_key_clean.sh user site1 site2 site3 site4

user=$1
hostlist=`echo "${@:2}"`

for hhost in $hostlist; do
  ip=$(dig +short $hhost)
  if [ -z "$ip" ];then
    echo "ERROR: couldn't get ip for host $hhost"
    exit 2
  fi
  sudo -H -u $user bash -c "ssh-keygen -R $hhost"
  sudo -H -u $user bash -c " ssh-keygen -R $ip"
  sudo -H -u $user bash -c "ssh-keyscan -H $ip >> ~/.ssh/known_hosts"
  sudo -H -u $user bash -c "ssh-keyscan -H $hhost >> ~/.ssh/known_hosts"
done