Notify > file / challenges

I am trying to use the notify > file for exporting entity and its attributes
Two issues for which I do not find a simple solution

  1. the generated file is appended with each ‘notify’, instead of overwriting it. I do not know if overwrite exists (doc does not say so) so would I then need some command_line to delete it?
  2. the generated file contains two header lines which (also for me) add no value at all, also here the doc does not help, so would I then need another some command_line to delete them (I use grep -vE)?

All in all, the notify>file seems quite rigid (to me)