Tutorials about file I/O?

Hi people.

Im making some progress in my quest to learn C, but Im having some problems finding good information about reading/writing files, well beyond just reading lines and typing them to the stdout anyways.

Im looking at stuff like having configuration files, which requires a bit more.

Im going to get myself a book or two, but until I do, I'd love to have some online information.

Does anyone know any good sites with tutorials that dont just briefly touch the fgets, etc functions, but actually goes a little deeper?

Oh and while Im asking, are there any particular books that are better than others?
There are quite a few book on the main page, and Im having a hard time deciding which oens to get.
Right now Im thinking I'll get "The C programming language", since I've read much of "The C++ programming language", and it was a good reference book.
Aside from that Im also thiking a good tutorial style book would be good.

Thanks.

//Sunner

http://www.cprogramming.com/cboard/s...threadid=10358

Haven't really looked, but seems to have some good stuff...

Anyway, try google - bet it helps

Reading/writing files is relatively straight forward. You use a function like either fread() or fwrite().

Essentially any I/O storage device is a "block" device. This means that it isn't really engineered to read/write data in tiny (byte-size) quantities. You can, but that's misusing the power of the device itself.

No, block devices prefer to be read/written in large "blocks" of data. 100K, 500K, or more. That's where they really shine.

Understanding that means that rather than reading file data in in byte-size bits, you read in as big a block as is reasonable (100K, 50K, 10K, or larger like 1MB, or more depending on RAM).

Same thing with writing.

Since RAM is _so much faster_ than disk I/O, you want to do bulk reads and writes and then do your manipulation all in RAM. Makes for faster, more effecient programs.

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With the above basic understand, let's think about how we might use this:

Well, instead of using fgets() to get a dribbling amount of data, you could ideally use fread() with a structure, or list of structures.

A single diimension array of data is essentially a consecutive list of like elements. Because this is the case, you can actually read and write entire arrays as a single block of data from/to a drive.

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File basics--

You can read data
You can write data
You can position the drive head within the file
- Positioning is relative to the start of the file
- Positioning can be relative to the end of the file
- Positioning can be wherever the head is at


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Normally you open a file and get a FILE* pointer to it. This means the code creates a I/O buffer (at the driver level) and allocates a structure with a variety of other information about the file in question.

You access this file by referencing the FILE*.

In order to read from a file, you must create your own buffer (malloc() can do that) of sufficient size to contain the data you want to read in. To write to a file, you must already have a buffer allocated with the data you want written, and you must pass it's address to the fwrite() routine so the disk driver knows where to pull data from.

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What else would you like to know?