Cron every hour

January 28, 2021 No comments Cron Quartz Job Scheduler Java crontab

1. Introduction

In this article, we are going to present cron expressions which are responsible for executing specific task every hour. Cron expression is a special format used for defining time for scheduled tasks.

2. Cron expression every hour for crontab

In Linux operation system there are a special crontab files used to configure cron jobs. Each line in the crontab file contains six fields separated by a space followed by the command to be run. The cron expression for crontab daemons that execute task every hour looks like the following:


We can break down the expression into the following components:
  1. 0 - at minute 0,
  2. * - every hour,
  3. * - every day of the month,
  4. * - every month,
  5. * - every day of the week.

Example crontabs:

Run PHP script every hour:
0 * * * * /usr/bin/php /home/username/public_html/cron.php >/dev/null 2>&1

Create MySQL dump every hour:
0 * * * * mysqldump -u root -pPASSWORD database > /root/db.sql >/dev/null 2>&1

Run bash script every hour:
0 * * * * /bin/bash /home/username/backup.sh >/dev/null 2>&1

3. Cron expression every hour for Spring Scheduler

In Spring scheduler a cron expression consists of six sequential fields: second, minute, hour, day of the month, month, day(s) of the week. In Spring cron expression use to run tasks in 5-minute intervals looks like the following:


Let's break down the expression into separate components:
  1. 0 - at second :00,
  2. 0 - at minute :00,
  3. 0/1 - starting at 0 every 1 hour,
  4. 1/1 - starting at 1 every 1,
  5. * - every month,
  6. ? - any day of the week.

Note that:
  • for the minutes, hours, and day of week columns the 0/1 and * are equivalent as these are 0 based.
  • for the Day Of Month and Month columns 1/1 and * are equivalent as these are 1 based.
According to that our cron expression could also looks like: 0 0 * * * ?

Example Spring scheduler configuration that executes task every hour:

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;


@Component
public class MyScheduler {

    @Scheduled(cron = "0 0 0/1 1/1 * ?")
    public void doSomething() {
        // this code will be executed every hour
    }

}

4. Cron expression every hour for Quartz

The Quartz is an open-source scheduling tasks library for Java application. Quartz expression has seven parameters: The last one stands for the year.


The following snippet creates a simple cron scheduler using Quartz library:

JobDetail job = newJob(SimpleJob.class)
    .withIdentity("job1", "group1")
    .build();

CronTrigger trigger = newTrigger()
    .withIdentity("trigger1", "group1")
    .withSchedule(cronSchedule("0 0 0/1 1/1 * ? *"))
    .build();

sched.scheduleJob(job, trigger);

5. Conclusion

In this article we presented several cron expression used for executing task every hour. Presented crons are ready to copy/paste.
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