viktor:

If you're on a unix box, then you can glue files together like this:

generatefile foo
cat foo >>the_big_file
generatefile foo
cat foo >>the_big_file
[download]

So you can use the same trick in your script. If you're on DOS, there's a similar trick using copy, but you'll have to read the help page on it, as I don't recall it well.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

So you neither want to override the files, nor do you want to preserve them. What do you want?

and it is a long file so i cannot generate hundreds of files

Uhm, why not? A decent computer can handle hundreds of long files, whatever that means.

If disc space is an issue, you could compress the files after they are generated. Or extract the information you want from them, and then delete them.