OS=`uname -s`
RSH="rsh -l user"
RSH2=""
PING="ping -c1 -w 3"
PING2=""

case $OS in
   HP-UX*)
           PING=ping
           PING2="-n 1"
           RSH="remsh"
           RSH2="-l user"
      ;;
   SunOS*)
      PING="ping"
      PING2=""
      ;;
esac
...

for i in server1 server2 server3 workstation1 workstation2
do
$PING $i $PING2 > /dev/null
        if [ "$?" != "0" ]; then
                echo 
                echo " Couldn't reach Host $i !"
                echo
      continue
        fi
$RSH $i $RSH2 uptime
done