Tvheadend

What is the command that tvheadend uses to generate the EPG database? I am using mc2xml and modified a /usr/bin/tv_grab_file to simply cat an already generated XML file. I've pointed the web interface in Configuration->Channel/EPG->EPG Grabber to use this new XMLTV option, but my EPG is still blank.

I've tried adding some simple debug statements in the /usr/bin/tv_grab_file script to touch an empty file when it is invoked, and the file never gets created

#!/bin/bash
echo "$@" >> /home/hts/mc2xml/args
echo "test" >> /home/hts/mc2xml/test

dflag=
vflag=
cflag=
if (( $# < 1 ))
then
  #cat ~/.xmltv/tv_grab_file.xmltv
  cat /home/hts/mc2xml/xmltv.xml
  touch /home/hts/mc2xml/grabbed
  exit 0
fi

...snipped...

In the debug log on the interface, I see messages such as:

2015-05-07 02:42:00.005 spawn: Executing "/usr/bin/tv_grab_file" 
2015-05-07 02:42:00.006 /usr/bin/tv_grab_file: no output detected
2015-05-07 02:42:00.006 /usr/bin/tv_grab_file: grab returned no data

But I know this isn't the case since executing the script manually, I get a huge output. I suspect this command isn't being executed at all since my "grabbed" file never exists.

What I need to know is where/how does the EPG get generated and perhaps I will just setup a crontab to invoke it.

Or perhaps this is just a bug in the version of tvheadend I am using. I am currently on build: 3.9.2813~gdec62bf~trusty