Run Cronjob from Web server

I have a Pi that has motion installed and working. I am consuming this and displaying it on a page that is also running on my LAMP stack on the Pi. I don't want the camera to run all of the time and would like the ability to start and stop the motion service (via cronjob) by clicking a link on the page. So the all in all is I need to execute a cronjob by clicking a link on the site. Ideas?

This will all be secured behind a firewall and if made public with a username and password so you can skip the risk speech on this one.

Former Member over 12 years ago

There are some examples here using javascript:
http://stackoverflow.com/questions/5636051/cronjobs-in-node-js
depending on whether you're worried about restarts.
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Former Member over 12 years ago in reply to Former Member

Restarts are not a problem as I have some cron jobs in place to handle that.

I am not a Java programmer so you may have to bare with me. I am not looking to schedule jobs with js but rather to fire one with it with a click of a link.

example:

Link would be "Start Motion"
on click would do - sudo service motion start

So a cron job may not even be necessary but they already exist. Launching a command with a link click would work as well.
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Former Member over 12 years ago in reply to Former Member

Javascript is different from Java. Just unfortunately similar names.
Edited to clarify: Javascript can be run either client-side or
server-side. I think you want server-side.
see http://en.wikipedia.org/wiki/Server-side_scripting

Instead of Javascript, you might be better off with PHP for
server-side scripts. In PHP, you can execute a shell command
using shell_exec() or exec().
http://stackoverflow.com/questions/7540847/html-button-to-call-php-shell-exec-command
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Former Member over 12 years ago in reply to Former Member

I have changed directions and am now going down the path of using cgi scripts. I have the scripts running from the web but the "service start" comand never fires.
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Problemchild over 12 years ago in reply to Former Member

A Cron job is something quite independant to the webserver call.#
The Motion S/W can be started and stopped via Startup/Shutdown scripts put into the Crontab via a comman like crontab -e orwhat ever tool you have used to edit the file.

You could have this ssytem run independantly to the "on demand" web call but in both cases you would need to have a check inthe startup script to check it wasn't already running and also have the shutdown script not complain too much if the Motion S/W has been stopped already by the web script for example.

Another way would to have the Web server call touch a file when you want to start or stop the Motion S/W then have a Crontab script check it every min and stop or start motion appropriately ...Remember that cron has a granularity of 1 min here !!
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Former Member over 12 years ago in reply to Former Member

Hi coder27,
I got a simple question,, I am only leary of power surges,,, but may I plug my R-pi into a power strip and just turn everything on and off with it ?
Sonny
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mgt6910 over 12 years ago in reply to Former Member

The shutdown that you propose is exactly what I do after entering the command "sudo shutdown now". Wait 30 seconds for a few lines of shutdown messages, then throw that switch. Ditto for startup, I have everything on a strip: screen, Pi, USB-Hub. No problems.
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