Cron every minute

1. Introduction

The cron is a time-based function used for scheduling jobs. In this short article, we are going to present how to create a cron expression that will be used to run tasks every minute.

2. Cron expression every minute for crontab

A crontab is a special file in unix system with instructions for 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 minute looks like the following:


We can break down the expression into the following components:

1. * - means every minute,
2. * - every hour,
3. * - every day of the month,
4. * - every month,
5. * - every day of the week.

Example crontabs:

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

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

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

3. Cron expression every minute for Spring Scheduler

In Spring scheduler a cron expression contains 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 1-minute intervals looks like the following:


Let's break down the expression into separate components:

1. 0 - at second :00,
2. 0/1 - every minute starting at minute :00,
3. * - every hour,
4. * - every day,
5. * - every month,
6. ? - any day of the week.

Example Spring scheduler configuration that executes task every minute could have the following structure:

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


@Component
public class MyScheduler {

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

}

4. Cron expression every minute for Quartz

The Quartz project is an open-source task scheduling library that can be integrated with any Java application. Quartz in comparison to Spring scheduler has the additional 7th parameter in cron expression that stands for the year.


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

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

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

sched.scheduleJob(job, trigger);

5. Conclusion

In this article we presented quick tip for creating cron expression that executes specific task every minute. We created ready to copy/paste snippets for Spring applications, Quartz library, and linux crontab.