1.把定时任务写到一个文件里面

*/1 *1 * * * echo "hello" >> tt.txt

2.使用shell读取定时任务文件写入到 crontab 里面

#!/bin/bash
# 1.start crontab
/bin/systemctl start  crond.service
# 2.remove old crontab
echo > /var/spool/cron/website
# 3.add crontab
cat cron.txt | while read line
do
    echo "$line" >> /var/spool/cron/website
done
# 4.reload crontab
/bin/systemctl reload  crond.service