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Sorry to post them quick and thick, but when one problem is solved, ten other follow. I'm sure we all know how that is.

Basically, I'm wondering how much of a file should remain loaded in memory until it's freed. I mean, you fopen a file and you've got this pointer hanging around and you're fseeking in it, but should the OS keep updating like a 1kb buffer for the file, or does it allocate more as it goes up to a point?

Also, I understand that successive reads to a file can be much simplified on an ext2 or 3 implementation because you can just keep track of a single inode number and then use that to reference the rest of the file. With other file systems like VFAT and etc. still have one little datum that I can store to quickly re-lookup a file? The reason I ask is that I'm thinking of the generic file pointer for a file on any fs, and how I can generalize it.

wangpeng wrote: Basically, I'm wondering how much of a file should remain loaded in memory until it's freed. I mean, you fopen a file and you've got this pointer hanging around and you're fseeking in it, but should the OS keep updating like a 1kb buffer for the file, or does it allocate more as it goes up to a point?

You might want to have a closer look at <stdio.h>, more specifically the setbuf() function and the BUFSIZ macro. In a nutshell, C assumes a fixed-size buffer and allows the user to set the buffer (and its size) explicitly.