How can we schedule automatic tasks in Unix

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Stratos Matzouranis

The journey began in 2008 where I officially started working in the field of IT (IT). Starting the first semester of school I realized a special attraction towards databases and automation. I have been involved with databases such as Microsoft SQL Server / Oracle Database, data analysis and automations using the command line (CLI), Visual Basic for Applications and Python. Through years of experience I have developed these capabilities so that I can make my life easier. For me, the purpose of every IT guy and every office worker is to have the knowledge so that through tools he can work a little but produce a lot. Through this his website DataPlatform.gr I try to offer knowledge and propose solutions to everyday problems.

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Unix-based operating systems such as Linux and MacOS have the Cron program installed.

Cron allows us to schedule tasks to run automatically over time.

Its usefulness stands out in repetitive tasks.

The editorial

To see the list of all the schedules we already have in cron

crontab –l 

To add new schedules or change existing ones

crontab –e 

Each entry is a separate program.

The way it is drafted

# ┌───────────── λεπτό (0 - 59)
# │ ┌───────────── ώρα (0 - 23)
# │ │ ┌───────────── μέρα (1 - 31)
# │ │ │ ┌───────────── μήνας (1 - 12)
# │ │ │ │ ┌───────────── ημέρα της εβδομάδας (0 - 6) (0 είναι η Κυριακή)
# │ │ │ │ │                                  
# │ │ │ │ │
# │ │ │ │ │
# * * * * * <η εντολή που θα εκτελεστεί>

The order in the asterisks is minutes 0-59, hours 0-23, day 1-31, month 1-12, day of the week 0-6 with 0 being Sunday to begin with. However we can select some days by putting ' , ' between the days.

Examples

To run the test.sh file

Every 5 minutes

*/5 * * * * /home/user/test.sh

Every hour

0 * * * * /home/user/test.sh

At 10 in the morning

0 10 * * * /home/user/test.sh

Every Monday at 10:15 am

15 10 * * 1 /home/user/test.sh

Every first and 15th of the month at 8 am

0 8 1,15 * * /home/user/test.sh

To see the log

tail -f /var/spool/mail/onoma_xristi

Sources:

• Cron Wiki