Make connecting to huge lists of new hosts easier with this simple ssh hostkey importer (using ssh-keyscan)

keyscan

#!/bin/bash
hostlist=$1
outputfile=$2
if [ -z "${2}" ];then
	outputfile=~/.ssh/known_hosts
fi
time while read -r host; do
	ip=$(dig +short "$host" 2> /dev/null)
	#remove the key from the file
	ssh-keygen -R "$host" -f "$outputfile" >/dev/null 2>&1;
	ssh-keygen -R "$ip" -f "$outputfile" >/dev/null 2>&1;
	#scan for the new key
	ssh-keyscan "$host" 2> /dev/null >> "$outputfile" && echo "Added hostkey for $host to $outputfile";
	if [ ! -z "${ip}" ]; then
		ssh-keyscan "$ip" 2> /dev/null >> "$outputfile" && echo "Added hostkey for $ip to $outputfile";
	fi
done < "$hostlist"
sort -u "$hostlist" -o "$hostlist"