when-down

#!/bin/sh
#
# Wait until a given host is down (determined by ping) then execute the
# given command
#
# Usage:
# ./when-down HOST COMMAND...
#
# Example
# ./when-down 1.2.3.4 ssh 1.2.3.4
#


#
#  Ensure we received the correct number of arguments.
#
if [ $# -lt 2 ]; then
    echo "Usage: when-down HOST COMMAND..."
    exit 1
fi

HOST=$1

echo "Waiting for $HOST to get down..."

true
while [ $? -ne 1 ]; do
    ping -c 1 -W 1 $HOST >/dev/null
done

shift
$*