How do I setup a Cron job?

: This document is valid for 1&1 Web Hosting 5.0 but not for 1&1 Microsoft Hosting.

Automatize your tasks with cron

Cron jobs can help you to automate certain procedures e.g. backup. This article is a brief "how-to" for creating a cron field which defines when a specific application or script should be executed.

Execute the command crontab -e to generate or edit your cron-file. Alternatively use crontab -l for listing your cron jobs or crontab -r for deleting all cron jobs.

One line in the cron file looks like this:

1 2 3 4 5 /etc/myScript arguments

The five numbers at the beginning of the line represent the following:

1: minutes (0-59)

2: Hours (0-23)

3: Day     (0-31)

4: Month   (0-12 or January, February, ... 0 and 12=December)

5: Day of the week(0-7 or Monday, Tuesday, Wednesday, ... 0 and 7=Sunday)

This enables you to exactly define when a script is supposed to be started.

Wait, there is more! You can make the file even more flexible like this:

*:         applies every time

1-4:       start if 1,2,3 or 4 matches

1-4/2      step-by-step, here: 1 and 3

1,5,6:     enumeration

*/3:       every third

1-4,10-15: enumeration and range combined

Moreover you can define what SHELL is to execute the commands and who you want to send the results to (via e-mail):

SHELL=/bin/bash

MAILTO=me@localhost

A few more examples:

# every day at 0:05

5 0 * * *       $HOME/bin/daily.job >> $HOME/tmp/out 2>&1



# every first day of the month at 14:15

15 14 1 * *     $HOME/bin/monthly



# on weekdays at 22:00

0 22 * * 1-5   mail -s "It's 10pm" joe%Joe,%%Where are your kids?%



# every day 23 minutes after every even hour (0:23, 2:23, ...)

23 0-23/2 * * * $HOME/status.sh



# Sundays at 4:05

5 4 * * sun     $HOME/backup.sh full

Hint

Weekdays and calender days do not exclude each other but are considered separately. If either pattern matches the script will executed.

Print Article

Feedback

Overview	Search
Sitemap	Glossary