It is a bad news (at least for me) that this command will never get added

. The reason why i want this command:
I've a script which creates a txt file somewhere between 90Mb to 160Mb. It indexes every file on the hard disk with lots of details (Time created, Full Path, etc etc)... so i constantly need to delete this file and create again (Though few files are changed). So if this command was there... i could only check which File (Line) was not there in the current Loop (And Delete it-OR- Overwrite it) and if some file was not there(according to Drive, Or Extension) it will add it on the right spot... instead of the End of the File.
Anyways.,,
Thanks