crontab—timed task (pronounced: cron table)
1. Main timing tasks
/etc/cron.d/ This directory is used to store any crontab files or scripts to be executed.
Two, crontab main commands
crontab -e # 编辑定时任务
crontab -l # 表示列出所有的定时任务
crontab -r # 表示删除用户的定时任务，当执行此命令后，所有用户下面的定时任务会被删除，执行crontab -l后会提示用户：“no crontab for admin”
[Note: 5 stars in timed tasks]
* * * * *
Respectively
Minute, hour, day, month, week
Three, basic timing
| Features | command |
|---|---|
| Execute every 1 minute | * * * * * myCommand |
| Executed at the 3rd and 15th minutes of every hour | 3,15 * * * * myCommand |
| Executed at the 3rd and 15th minutes from 8 am to 11 am | 3,15 8-11 * * * myCommand |
| Executed at the 3rd and 15th minutes from 8 am to 11 am every two days | 3,15 8-11 */2 * * myCommand |
| Executed on the 3rd and 15th minutes from 8 am to 11 am every Monday | 3,15 8-11 * * 1 myCommand |
| Restart smb at 21:30 every night | 30 21 * * * /etc/init.d/smb restart |
| Restart smb at 4:45 on the 1, 10, and 22 of each month | 45 4 1,10,22 * * /etc/init.d/smb restart |
| Restart smb at 1:10 every Saturday and Sunday | 10 1 * * 6,0 /etc/init.d/smb restart |
| Restart smb every 30 minutes between 18:00 and 23:00 every day | 0,30 18-23 * * * /etc/init.d/smb restart |
| Restart smb every Saturday at 11: 00 pm | 0 23 * * 6 /etc/init.d/smb restart |
| Restart smb every hour | 0 */1 * * * /etc/init.d/smb restart |
| Between 11pm and 7am, restart smb every hour | 0 23-7/1 * * * /etc/init.d/smb restart |
Example: output the print result of a function in a shell to another file every minute
After entering the edit mode, output the following code
* * * * * sh /opt/test/func.sh >> /opt/test/a.txt
[Supplement: The function of func.sh is to output hello world]
View the a.txt file under test The
result shows:
