The running of the cron job for its tasks, jobs, or processes at specific intervals is provided by Linux. These intervals can be annual, in months, weeks, or configured in days. The interval of minutes is commonly used to run a cron job currently.
Can I run a cron job? If yes, how then can it be achieved at every minute?
Running a cron job is possible and can be done at each minute interval.
The /etc/crontab file is where the cron jobs can be seen. By default, this crontab file includes a few jobs. These current tasks are carried out in the space of intervals. The crontab file is formatted to be cat /etc/crontab.
Using the crontab instructions, a task that runs at every minute can be added. The -e option can be used to edit the crontab file with the rights of the current user.
Crontab — e
To create a file at “/tmp/test,” we will use the touch command in this example.
* * * touch/tmp/test
Synthax
To run a synthax for a cron job, the time has to be mentioned first before the command you want is carried out. The synthax responsible for time is divided into a field of five.
* * * * * command(s)
The first is for the minute.
The second is for the hour.
The third is for the month’s day.
The fourth is for the month.
The fifth and last field is for the week’s day.
All potential values for a field are known by the asterisk (*) operator. For example, when you put an asterisk in hour space it will mean every hour, but when you put it in the month’s space it will mean each month. A star in a field indicates that the command or script should be carried out at each minute.
What does a Linux cron job do?
A command-line tool called cron allows you to schedule the planning of short, simple instructions. This useful, traditional administrative system tool can be used together with other programs to automate different kinds of events.
For example, certain people make use of rsync and cron to plan a backup to be created all day or every week at a particular time. Some users use it to check server logs and join it with the mail function to send emails when some types of errors are found.
Similar to the Swiss Army Knife is a cron. It has several potential applications. What you decide to do with it is up to your imagination.
Difference between a crontab, cron, and cron job
You must have come across these three terms which have similar sounds. Cron job and crontab are derived from the word cron.
Let’s quickly see the difference between the three of them:
~ Crontab constitutes the file where specific instructions are given depending on how you want to use it. Different cron jobs are found in a crontab which is ordered in rows and columns.
~ Cron is the program that gets on your laptops, androids, or apple system when it is installed. It functions like a daemon.
~ Cron job can be said to be those tasks that are handled in cron at each given time.
How can a cron job be carried out within 10 minutes intervals?
It can be achieved in two ways within the 10 minutes interval.
It is first done by the use of a comma to separate the minutes’ list; for example, to have a script after 10 minutes interval, you write the syntax of the cron job as:
0, 10, 20, 30, 40, 50 * * * *
/home/linuxuser/script.sh
Isn’t this a little bit of a challenge? Writing each minute when you have an easier way to quickly present your synthax for a cron job at 10 minutes intervals.
*/10 * * * *
/home/linuxuser/script.sh
Conclusion
The usage of cron jobs is for the smooth running of the commands in a particular time interval so that the systems can be updated, their data backed up, and managed effectively.
We have been enlightened on how to carry out cron jobs at each interval, and the difference between crontab, cron, and cron jobs.
FAQs
How can a cron job be carried out at the interval of 20 minutes?
Just like we did for ten minutes, we can adopt the same pattern here.
*/20 * * * * /home/linuxuser/script.sh
How can a cron job be carried out at the interval of 30 minutes?
We will still adopt a similar pattern of the 10 and 20 minutes interval here.
That is, */30 * * * * /home/linuxuser/script.sh
Can crontab run in order?
Yes, crontab does run in order. The system makes sure that commands run in sequence, one at a time.
