as soon as the server replies to ping, do something

ifping.sh

#!/bin/bash
# ifping.sh
# f varas 10 2012

##
## you need to have sshpass or ssh-key
## to grant "passwordless" access to the servers

# execute an action when remote server replies to ping
counter=1

USAGE="usage: $0 hostname {uptime|uname|fallback|script}"

if [ -z $1 ]; then
  echo "$USAGE"
  exit 1
else
  while true; do
    ping -c1 $1 > /dev/null
    if [ $? == 0 ]; then
      echo "doing $2"
      if [ -z $2 ]; then
        echo "please, be more specific"
        exit 2
      else
        case $2 in
        uptime)
        ssh $1 'uptime' 
        ;;
        uname)
        ssh $1 'uname -a' 
        ;;
        fallback)
        ssh $1 echo "\`timeout -s SIGKILL 10 grep -i fall /var/log/syslog  | tail \`"
        ;;
        script)
        ./script.sh $1
        ;;
        *)
        echo "$USAGE"
        esac
      fi
      exit 0
    else
      echo "$1 unreachable, tried $counter times"
    fi
  sleep 5
  let counter++
  done
fi