Crontab

Crontab is a tool in Linux which automates tasks that need to be executed at specific times or intervals. This can include tasks such as backups, cleaning up temporary files, sending reports, updating software, and much more.

One of the benefits of using crontab is that it allows you to free up your time by automating repetitive tasks. Instead of having to manually perform a task at a specific time or interval, you can set up a crontab schedule to do it for you automatically.

Crontab is also useful for ensuring that tasks are executed consistently and reliably. By setting up a crontab schedule, you can be sure that a task will run at the exact time or interval you specify, regardless of whether you’re available to run it manually.

Another benefit of using crontab is that it can help you avoid human error. When you perform a task manually, there is always a risk of making a mistake or forgetting to perform the task altogether. By automating the task with crontab, you can eliminate this risk and ensure that the task is performed correctly every time.

Here is an overview of how to use crontab:

Open your terminal and type crontab -e to open the crontab editor.

Each line in the editor represents a task you want to schedule. The format of a crontab line is as follows:

*     *     *     *     *  command to be executed
-     -     -     -     -
|     |     |     |     |
|     |     |     |     +----- day of the week (0 - 6) (Sunday=0)
|     |     |     +------- month (1 - 12)
|     |     +--------- day of the month (1 - 31)
|     +----------- hour (0 - 23)
+------------- min (0 - 59)

The first five fields represent the schedule of the task, and the last field is the command you want to execute. After you’ve added your task, save the file and exit the editor. Crontab will automatically start executing your task according to the schedule you’ve set.

Here are some examples of crontab commands:

0 0 * * * /path/to/backup-script.sh

To run a backup script every day at midnight

0 3 * * 0 /path/to/cleanup-script.sh

To clean up temporary files every week on Sunday at 3am

0 8 * * * /path/to/send-report.sh

To send a daily email report at 8am

0 9 * * 1-5 /path/to/command

To run a command every weekday at 9am

0 4 * * * apt-get update && apt-get upgrade -y

To update your system every day at 4am