Run an magento function cron at every hour

Question

I want to run an magento function that would run at every hour , i am written code in config.xml but i did not working.here the code is

<crontab>
            <jobs>
                <stockalert_autosend>
                <schedule><cron_expr>**/1 * * *</cron_expr></schedule>
                <run><model>stockalert/observer::backinstock</model></run>
            </stockalert_autosend>
            </jobs>
        </crontab>

Please help me

Answer 1

Use this cron expression for each hour:

<cron_expr>0 * * * *</cron_expr>

This will make it run at 12.00, 1.00 and so on.
If you want to make it run at 12.30, 1.30 and so on replace 0 with 30