注：原脚本存在大量重复报警的问题，改写后问题得以解决


实现一：借助临时文件

#!/bin/bash
#
PF=0
while true
do
     touch /tmp/reppoe.txt       
     PPP=`ifconfig -a | grep -o ppp`
     PING=` ping -c 4 www.baidu.com 2>&1 | grep ttl | wc -l`
     LINE=`cat /tmp/reppoe.txt | wc -l`
  if [ "$PPP" != 'ppp' ] || [ "$PING" -eq 0 ];then
     echo "`date` pppoe is down" >> /tmp/reppoe.txt
    if [ $LINE -gt 20 ]; then
            echo "pppoe is dowm " | mail -s "pppoe is down" mailaddr && PF=1
            true > /tmp/reppoe.txt
    fi
           adsl-start;
               PING2=` ping -c 4 www.baidu.com 2>&1 | grep ttl | wc -l`
    if  [ $PING2 != 0 -a  $PF != 0 ];then         
            IP=`LC_ALL=C ifconfig | grep -P -A2 "ppp" | grep 'inet addr' | cut -d: -f2  | awk '{ print $1}'  `
            echo "pppoe is up and ip is $IP" | mail -s "pppoe is up" mailaddr && PF=0
    fi
  fi
sleep 10
done




实现二：

#!/bin/bash
mfcount=0
while true
do
PPP=`ifconfig -a | grep -o ppp`
PING=` ping -c 4 www.baidu.com 2>&1 | grep ttl | wc -l`
[ "$PPP" != 'PPP' ] || [ "$PING" -eq 0 ]
        status=$?
    if [ $status != 1 ] ;then
        mccount=`expr $mfcount + 1`
        [  $mfcount -lt 1  -o  $mccount -gt 3  ] && echo "pppoe is down" | mail -s "pppoe is down"  mailaddr && mfcount=`expr $mfcount + 1`
        ppstatus=1
           while [ $ppstatus != 0 -o $PING = 0 ]
                 do
                    adsl-start;
                    ppstatus=$?
                    PING=` ping -c 4 www.baidu.com 2>&1 | grep ttl | wc -l`
                          if [ $PING != 0 ] ;then
                              echo ok && echo "pppoe is up and ip is $IP" | mail -s "pppoe is up" mailaddr && mfcount=0
                          fi
                    sleep 3
           done
        IP=`LC_ALL=C ifconfig | grep -P -A2 "eth0" | grep 'inet addr' | cut -d: -f2  | awk '{ print $1}'  `
    fi
sleep 10
done