C file handling

**valar_king** · 01-22-2002

I have been try OVER and OVER to make a C program that opens a file and parses it. Can anyone explain the C system or just point me to a tutorial that does? And what can I use to make binary files?

Thanks,
Valar_King

**Shiro** · 01-22-2002

I don't know what you mean with parsing a file. But here are some hints which I hope help you further.

Code:

FILE *myfile;

/* Open the file myfile.dat as binary for reading */
myfile = fopen ("myfile.dat", "rb");

while (!feof (myfile))
{
    byte = fgetc (myfile); /* read a byte */
    fputc (byte); /* write a byte */
}

/* Close the file */
fclose (myfile);

Note: a byte is a variable of type unsigned char.

**quzah** · 01-22-2002

> fputc (byte);

Slight problem: You didn't specify the file to put to. Potential secondary problem: You've only opened one file, and since you aren't using update mode, you can't put to it.

Additionally, there is no 'byte' data type in C.

Quzah.

**Shiro** · 01-22-2002

Yep. Correct, forgot that.

Code:

fputc (byte, destination_file);

This destination_file should be opened as binary updating, which was "r+" I guess.

Code:

destination_file = fopen ("destination_file.dat", "rb+");

>Additionally, there is no 'byte' data type in C.

What I meant was: if you want to use bytes, the variables which are representing the bytes should be of type unsigned char.

Code:

typedef unsigned char byte;

**Salem** · 01-22-2002

> typedef unsigned char byte;
Which is no good for storing EOF, so you do not detect the end of file properly

The archetype copy a file a byte at a time is

Code:

int ch;  // must be int
FILE *myfile;

/* Open the file myfile.dat as binary for reading */
myfile = fopen ("myfile.dat", "rb");

while ( (ch = fgetc (myfile) ) != EOF ) {
    fputc (ch, stdout );
}

/* Close the file */
fclose (myfile);

**valar_king** · 01-22-2002

By parsing I meant going through the file and looking for data. The thing I am learning this for is 3d file formats in OpenGL. NeHe has a good tutorial that will hand me the code, but I'd much rather learn how to work with files. Say I make a struct like this:

Code:

struct pixel {
 int x, y, z;
 int r, g, b;
};

That's an example struct I could use. I'd like the program to open a file and read values for an array of pixel or other types of structs. Another example closer to my final goal.

Code:

struct vertex {
 float x, y, z;
 float u, v;
};

struct quadface {
 vertex points[4];
};

I'd like some code to read a file and grab the data for that points object according to a pattern or format. The type of file I am working towards is .md2 Quake2 models, but that's a long way off.

I hope that explains what I am trying to do. Any help would be appreciated. Thanks for the quick replies.

Thanks,
Valar_King

BTW What program should I use to make binary files?

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