shell判断某进程是否仍存在

#!/bin/sh
while :                          #循环，为了让脚本一直运行监控
do
sleep 60                        # 每次监测时间60秒
DTTERM=`pgrep nfsd`     #nfsd 为nfs进程名
if [ -n "$DTTERM" ]
then  echo "nfs service is ok" >> /var/log/nfs-mrtg.log 
#正确输入信息到日志文件
else
  echo "nfs servicie not exist" >> /var/log/nfs-erro.log
  /etc/init.d/nfs restart
  /etc/init.d/portmap restart
fi
done