Why do you want to prepend?

It's probably wiser to cope with the weaknesses of flat files by avoiding them (the weaknesses) altogether and concentrating on their strengths.

It is more efficient to read a file backwards (by seeking backwards from the end, reading in a chunk and looking for an end-of-line) than it is to prepend data to a file.

-sauoq
"My two cents aren't worth a dime.";