定时shell 导出多个mysql数据库

每天定时备份所有数据库数据库名字在文件：dbfile中，定时清除3天前的备份文件

#!/bin/bash 
dd=`date +%Y%m%d`
backup_dir="/usr/soft/crontabshell/"
username="uname"
password="password"
for dbname in `cat ${backup_dir}dbfile`
do
     nohup   /usr/local/mysql/bin/mysqldump -u${username} -p${password}  -B $dbname > ${backup_dir}${dbname}_${dd}.sql    2>/dev/null &
     ####echo $?
done
find $backup_dir -ctime +3 -name "*.sql" -exec rm -rf {} \;