How to setup CRON job to run every 10 seconds in Linux?

Question

I need to run a CRON job every 10 seconds from started time.

In Linux how to run a CRON job on every 10 seconds from the time its started?

I am trying to solve that as following: when I make a request (or start) at 04:28:34 it should start at 04:28:44 not at 4:28:40

This is what I have done

# m h  dom mon dow   command
*/10 * * * * /usr/bin/wget http://api.us/application/

What did I do wrong? Why does this not trigger wget every 10 seconds?

Solution 1

To elaborate on Sougata Bose's answer, I think the OP wants a command to be run every 10 seconds from a start time; not 10 seconds after the first minute and every subsequent minute.

cron only has a resolution of 1 minute (there are other tools I think that may have finer resolutions but they are not standard on unix).

Therefore, to resolve your issue you need 60 seconds / 10 seconds = 6 cron jobs, each with a sleep.

e.g. run crontab -e and add the following lines to your chosen editor:

* * * * * ( /usr/bin/wget http://api.us/application/ )  
* * * * * ( sleep 10 ; /usr/bin/wget http://api.us/application/ )  
* * * * * ( sleep 20 ; /usr/bin/wget http://api.us/application/ )  
* * * * * ( sleep 30 ; /usr/bin/wget http://api.us/application/ )  
* * * * * ( sleep 40 ; /usr/bin/wget http://api.us/application/ )  
* * * * * ( sleep 50 ; /usr/bin/wget http://api.us/application/ )  

Solution 2

Another option is to edit your crontab with crontab -e and write:

* * * * * for i in {1..6}; do /usr/bin/wget http://api.us/application/ & sleep 10; done

Solution 3

*/10 * * * * will run every 10 min.
*/10 * * * * * will run every 10 sec.

You can checkout the cron editor for more options.

Solution 4

Using commas in seconds field works too:

0,10,20,30,40,50 * * * * *

Solution 5

If something should run every 10 seconds it does not have to be cron job. It can be a script with endless loop with sleep inside like:

while true
do
  # or whatever command you need to run
  rm -rf /var/www/some-directory
  sleep 10
done

and run it with

nohup bash my-endless-script.sh 

which will run it on background and will continue also if you shut down the terminal.

You can kill the run with kill command.

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