[Freeswitch-users] CDR using lua script

I am trying to insert CDR using a lua script. <action application="export" data="nolocal:api_hangup_hook=luarun cdr2.lua ${start_stamp} ${created_time} ${progress_time} ${progress_media_time} ${answer_stamp} ${end_stamp} ${duration} ${billsec}....." But when this executes many of the parameters passed to script as nil like billsec , How can I get all parameters related to CDR (Like other CDR modules)