The crontab command of linux is executed at the end of every three months

1. Basic usage of crontab:

Edit scheduled tasks

# crontab -e 

View all scheduled tasks

# crontab -l

delete crontask

# crontab -r

2. Commands executed on time-sharing days, months and weeks, for example:

①, logbak.sh content:

#!/bin/bash

#打包/var/log
tar -zcf /opt/shell/log-`date +%Y-%m-%d-%H-%M`.tar.gz /var/log

②, Execute logbak.sh once every minute

# crontab -e

* * * * * /opt/shell/logbak.sh

3. The meaning of * - and /n appearing in regular expressions

(1) Use the month to say:

*Equivalent to: 1,2,3,4,6,7,8,9,10,11,12

1-3 is equivalent to: 1,2,3

1,4,7,10 is equivalent to 1,4,7,10

*/3 is equivalent to 1,4,7,10

*/4 is equivalent to 1,5,9

4. If it is May 2019, it will be executed at 23:59 at the end of every three months

59 23 28-31 2,5,8,11 * [ `date -d tomorrow +\%e` -eq 1 ] && /opt/shell/logbak.sh