Defining Buffer size for write to file

Hi,
I am writing a code for an I/O Benchmark application in C and I need to change the block size of read and write of a file from and to a disk. I am not able to figure out a way to do that. Can some one help me out with this?
Thanks in advance.

I don't think if you can do it explicitly...

Is there any way to do it???

Is there any way to do this? cos I am not able to find any

What C functions are you using to read/write?
Edit: If you are using stdio.h functions, you could use setvbuf.

Thanks for that...

I am just wondering if the setvbuf function would change the size of the write or read block size?????

Which OS/Compiler are you using?

To get the most representative benchmarks, you need to use the lowest level API routines available from your OS.

The C standard API on top of that varies in complexity from one OS to another.