linux 监控进程是否存在

#!/bin/bash
while [ 1 ]
do
    MD_CAPTURE=`ps -ef|grep "md_capture.py"|grep -v grep|wc -l`
    if [ ${MD_CAPTURE} == 0 ];
        then
            cd /usr/local/CCDTSoft/midou/moss/task
        nohup python -u /usr/local/CCDTSoft/midou/moss/task/md_capture.py >> /usr/local/CCDTSoft/midou/moss/task/md_capture.log 2>&1 &
    fi
#   sleep 3
done
exit