On Wed, 2007-09-26 at 13:58 -0400, aragonx@xxxxxxxxxx wrote: > >> No, it doesn't. What purpose would that serve? It will cost you a > >> buffer > >> for the I/O (perhaps 8192 bytes) and a FILE control structure. > > > > If I remember rightly its nearer 64K nowdays simply because disks are > > faster, memory is cheaper and its a good buffer size. > > > > Basically the C library will make an intelligent decision on buffering > > which you should assume is right exept in very special cases. That value > > may change depending on library version, kernel, system memory, OS and a > > million other things but its there in the library to save you having to > > worry about it in the app. > > > > If you need to do specific buffering see "man setbuf" > > Thank you for your replies. I think I have a clear understanding of what > is going on but let me air what I think, then you can tell me how stupid I > am. :) > > Okay, so I use fopen and it gives me a stream. Now when I call fread (say > for 100K) on my large file (2G) it will try to read the first 64K > regardless of size and populate *ptr. If size is larger than 64K (100K > here) it will then read another 64K? Does it use the same buffer space > (effectively only using 64K) and is that buffer space outside the memory > footprint of my application? > > Again, thank you for all of your help. > Side question... do you -require- buffering? Using fXXXX on large files may produce noticeable performance hit. If you don't, open (2) may produce (far) better results. (As the price of having to do string parsing/new line searching yourself) - Gilboa
