🚀 go-pugleaf

>In article <25884@mimsy.umd.edu> chris@mimsy.umd.edu (Chris Torek) writes:
>In article <140087@sun.Eng.Sun.COM> jasonf@cetemp.Eng.Sun.COM
>(Jason Freund) writes:
>>"fwrite(pointer, sizeof, *pointer, items, stream)" which somehow magically
>>saves every piece of data (specified in the arguments) in such a way that it
>>will be able to read in every piece of data back into their correct cells in
>>the data structure?
>
>No.
>
>The primary rule of magic is this: `There is no magic'.  Fread and fwrite
> ...

    fwrite(ptr, blockSize, numBlocks, fi);

    const void *ptr;		pointer into memory, fwrite does not know or
				care what the pointer is actually pointing
				to!  const means the memory is not modified
				by fwrite() (obvious).

    int blockSize;		fwrite writes blockSize * numBlocks bytes
    int numBlocks;		of data from the memory location given by
				'ptr' to the file, no interpretation of the
				data is done.

    FILE *fi;			da file.


    Why am I interjecting what has already been said?  Because nobody has
    yet explained the one point that confused the hell out of me when I
    first started learning C, and that is WHY are there two size arguments?!!

    fwrite() simply multiplies numBlocks * blockSize to determine how many
    bytes to write to the file.  The ONLY difference between these two
    arguments is that fwrite() returns the number of successful blocks that
    were written, i.e. it returns  bytes_written_without_error / blockSize
    or a negative number on total error.  I do not even think fwrite() tries
    to keep low level flushes (write()s) on block boundries.

						    -Matt

--


    Matthew Dillon	    dillon@Overload.Berkeley.CA.US
    891 Regal Rd.	    uunet.uu.net!overload!dillon
    Berkeley, Ca. 94708
    USA