reading a writing x bytes

[punkCow]

I want to write a cross platform program that reads x bytes from a file, then writes x bytes to a file. I know how to do this under Linux. I would simply use:

#include <unistd.h>
write()
and
read()

Is there something on the fopen family I could use? Sorry if this is a stupid question.

TIA

[Thantos]

#include <stdio.h>

fopen : open the file
fgets, fscanf, fread : different function for getting the data
fprintf, fwrite : different function for writting the data
fclose : close the file


Now look that these function, write some code, and then post it so we can help you with any problems.

[punkCow]

Originally posted by Thantos
#include <stdio.h>

fopen : open the file
fgets, fscanf, fread : different function for getting the data
fprintf, fwrite : different function for writting the data
fclose : close the file


Now look that these function, write some code, and then post it so we can help you with any problems.

Do these functions let me read x numbers of bytes, or x charcaters? I'm looking for something that will let me read x numbers of bytes form a file (I guess thats stupid now that I think of it... will fgetc read one byte at a time?) *runs off to write some code*

[swoopy]

Use fread() and fwrite(). And make sure you open the file in binary mode.

[punkCow]

Originally posted by swoopy
Use fread() and fwrite(). And make sure you open the file in binary mode.

Thank you! I love it here, I can't say how happy it make me to see programming warriors helping the newbies like me :-D

Thank you everyone that has ever helped a newbie! :-D

[Prelude]

>Use fread() and fwrite(). And make sure you open the file in binary mode.
Not a good idea if the data files are intended to be used in a cross platform way as well as the program itself. fread and fwrite do what you would expect: work with a one-to-one mapping of memory and data file. This makes the files themselves as non-portable as it gets.

If the OP doesn't need to move the files around, fread and fwrite will suffice, but if the files do need to be moved around, a more robust solution is required. Unfortunately, that means writing your own binary I/O functions that make sure the data is written the same way everywhere. I touched on this issue here.

[punkCow]

Originally posted by Prelude
>Use fread() and fwrite(). And make sure you open the file in binary mode.
Not a good idea if the data files are intended to be used in a cross platform way as well as the program itself. fread and fwrite do what you would expect: work with a one-to-one mapping of memory and data file. This makes the files themselves as non-portable as it gets.

If the OP doesn't need to move the files around, fread and fwrite will suffice, but if the files do need to be moved around, a more robust solution is required. Unfortunately, that means writing your own binary I/O functions that make sure the data is written the same way everywhere. I touched on this issue here.

Does fputc and fgetc read/write one byte at a time? Would fgetc and fputc do the trick on a file opened in binary mode, or ould I still have to issue of not being cross platform?

Thank you, I'm a little slow ;-)

[Prelude]

>Does fputc and fgetc read/write one byte at a time?
Yes.

>Would fgetc and fputc do the trick on a file opened in binary mode
No. You would still have the problem of size, byte order, floating-point format, padding, etc... But if you can get away with using text files instead of binary files then all of these problems just go away.