FWrite best practice during loops - once or each loop?

[pepsi_max2k]

Hey all, just wondering about how I should best go about adding an fwrite command to a small loop...

 

I want to write one line to a file every time I pass through one loop. I could loop up to 20,000 times, around 50 bytes per line, around 1 MB if doing 20,000 entries.

 

So, do I fwrite for every entry (which I presume is taking up extra processing time) or do I continuously append lines to one super large up-to 1 MB string then perform a single fwrite once the loop has finished?

 

Thinking about it, that doesn't sound so great, I'm only fwriting to debug if something does wrong during the loop... one fwrite = no output at all if something goes wrong... I think I found my answer :|