In Ubuntu use Cron and Crontab to Run Schedule Tasks

Open/Close/Restart Cron in Ubuntu

Config file usurally is /etc/init.d/cron

Start: 

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sudo /etc/init.d/cron start

Close:

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sudo /etc/init.d/cron stop

Restart:

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sudo /etc/init.d/cron restart
sudo service cron restart

Reload config:

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sudo /etc/init.d/cron reload

Create a cron task

Normally we use “crontab -u username -e” to add new task in the cron config file.

If edit the exists task, the same command.

running command line

example to write “hello world” to /home/tonytan/helloworld.txt every 5 seconds.

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*/5 * * * * echo "hello world" >> /home/tonytan/helloworld.txt
use shell file
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*/5 * * * * /home/tonytan/helloworld.sh

Write the following codes into /home/tonytan/helloworld.sh

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#!/bin/sh
cd /home/tonytan/
echo "hello world" >> helloworld.txt

Note: after edit the config file everytime must restart cron, unless unuseable.

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sudo service cron restart
sudo service cron status    #look the cron status
crontab -l    #look the cron
crontab -e    #edit cron

Attached is the normally example in cron config:

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every 5 sec run task:
*/5 * * * * ?

every 1 min run task:
0 */1 * * * ?

everyday 23:00 run task:
0 0 23 * * ?

everyday 1:00 run task:
0 0 1 * * ?

every month first day 1:00 run task:
0 0 1 1 * ?

every month last day 23:00 run task:
0 0 23 L * ?

every Sunday 1:00 run task:
0 0 1 ? * L

in 26min,29min,33min run task:
0 26,29,33 * * * ?

every day 0:00,13:00,18:00,21:00 run task:
0 0 0,13,18,21 * * ?