Scheduling cronjobs at specified time
Can I suggest you look into using LaunchD. Cron is officially deprecated on OSX. LaunchD has a lot of really nice features too.

The plist files can be a pain at first, but you get used to them.

Something like this can help:

http://blog.mattbrock.co.uk/2010/02/25/moving-from-cron-to-launchd-on-mac-os-x-server/

It can be as simple as this:

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
    &lt;key&gt;Label&lt;/key&gt;
    &lt;string&gt;BatchFF&lt;/string&gt;
    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
        &lt;string&gt;/Users/sri/files/BatchFF.sh&lt;/string&gt;
    &lt;/array&gt;
    &lt;key&gt;StartCalendarInterval&lt;/key&gt;
    &lt;dict&gt;
        &lt;key&gt;Hour&lt;/key&gt;
        &lt;integer&gt;15&lt;/integer&gt;
        &lt;key&gt;Minute&lt;/key&gt;
        &lt;integer&gt;10&lt;/integer&gt;
    &lt;/dict&gt;
&lt;/dict&gt;


Save the file as batchFF.plist in ~/Library/LaunchAgents