Shell Programming and Scripting

cat serverlist | while read arg
do
        if [ -n $arg ]
        then
                echo "$arg"
                ping -c 4 $arg >> /dev/null
                if [ $? != 0 ]
                then
                        msg_body="msg_subst"
                        host=`nslookup $arg | grep name | sed 's/.*name = //'`
                        cat message | sed "s/srv/$arg - $host/" > msg_subst
                        cat admins | while read line
                        do
                                if [ -n $line ]
                                then
                                        echo "$line"
                                        mail -s Servizio_controllo_server $line                                                                              < "$msg_body"
                                fi
                        done
                fi
        fi
done