Thread: Reading binary files

I/O on binary files is done by fread() / fwrite(). The first call to fread() gets 2 ints worth of data (row and column). Now malloc() storage for the 2D array with those dimensions. Subsequent calls to fread() get no. of ints from the binary file equal to the no. of columns instead of just two.

Sorry I have no updated this in a while, I got carried way with other things. Anyways, I keep getting a segmentation fault when I run my program. Here is my code:

Code:

#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>


int main (int argc, char *argv)
{
FILE *fp;
float q;
int m;
fp=fopen("C:\\Users\\MyName\\Desktop\\Matrices\\matrixA.bin", "rb");
m=fread(&q, sizeof(q), 1, fp);
printf("\n%f and %i \n\n", q,m);


fclose(fp);

return 0;
}

Any idea whats wrong? And just to clarify, I said I was reading in two bytes before (which I still am going to need to do) but for now I am just doing one.

You need to test fp to make sure the file is opening correctly. If it doesn't you'll be asking your program to read from a null pointer....

How do I test for that? I've tried isolating different lines of code throughout the program, and the fread line is the only one that gives a segmentation fault when I run it. Could there be something wrong with the way I am reading the file from the folder on my desktop?

So I just wrote a quick little if statement after I try to assign the *fp a value to check if it still was equal to NULL and it was. So something is wrong with my fopen statement but I have no idea what. Any suggestions would be great. Thank you.

I am programming on a UNIX server which is why I included unistd.h. It prints "No such file or directory." I have also tried using a web address where the binary file is located as a download and I get the same error message. I suppose after further thought it would make sense for me to set up some sort of ftp to my computer, but I still don't know why the web address wouldn't work. Any suggestions? Thank you.

You speak of web address but your file name is a simple path name.
The fopen should work unless the file doesn’t exist (or doesn’t have read permission, or is locked, etc.)

Originally Posted by nonoob

You speak of web address but your file name is a simple path name.
The fopen should work unless the file doesn’t exist (or doesn’t have read permission, or is locked, etc.)

Yes I know I have a pathname in my code, I was just saying I tried a web address as well.

So you want it to work for web address? That would take more than what an fopen can do as far as I know. Sorry I can't help you there.

I have tried slashes both ways, using both one and two slashes. I have no idea how to read this file on my system from this UNIX server. Any and all suggestions are greatly appreciated.