#!/bin/sh

ips="192.168.178.79 192.168.178.52 10.7.0.1 none"

for ip in $ips
do ping -i .2 -c 1 "$ip" > /dev/null 2>&1 && break 
done

if [ "$ip" = "none" ]
then
	>&2 printf 'No ip.\n'
	exit 1
fi

sed -i "/Host db/,/^$/s/.*HostName.*/\tHostname $ip/" "$HOME"/.ssh/config
>&2 printf 'Done: %s \n' "$ip"