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Scheduling

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Scheduling with cron

Cron is used as the de-facto job scheduler for Unix.

Cron stands for “chronograph”.

Every user can specify scripts or programs to run at specific time intervals in a text file called “crontab”.

Example crontab file

Access/edit crontab file:

crontab -e

scheduling

scheduling1

cron job definition

* * * * * command to execute

|-->Day of week (0:Sunday to 7)
|-->Month (1 - 12)
|-->Day of month (1 - 31)
|-->Hour (0 - 23)
|-->Minute (0 - 59)

cron shortcuts

Entry Description Equivalant
@reboot Run once at starttup -
@yearly Run once a year 0 0 1 1 *
@annually Same as @yearly 0 0 1 1 *
@monthly Run once a month 0 0 1 * *
@weekly Run once a week 0 0 * * 0
@daily Run once a day 0 0 * * *
@midnight Same as @daily 0 0 * * *
@hourly Run once every hour 0 * * * *


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