Thread: extracting and printing data from a .dat file

I've been given an assignment to calculate the determinant of a 3x3 matrix which I must read from a .dat file. The contents of the .dat file should look something like this:

1 3 2
2 3 3
1 2 2

Basically, I can't work out how to read these values from the .dat file and print them in my program. If anyone can offer any help I'll be very grateful, thanks in advance

EDIT: what I have so far.

Code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char* argv[])
{
	FILE        *input;
	float       v1[3], v2[3], v3[3];
	const char  inp_fn[]="matrix.dat";
	
	input = fopen(inp_fn, "r");

Two basic approaches:

1. .dat is a text file and you read strings from it, then use scanf() or atoi() on the string
2. .dat is a binary file and you read datatypes (such as int) directly

Probably you want to do the former, as this makes creating and checking the .dat file easier. So you read a line of text with fgets(), then you pull numbers from it with sscanf(), or else you use fscanf() to do both.

Originally Posted by z0diark

P.S. I'm very inexperienced at C Programming so sorry if it takes a while for me to understand.

That's fine, but you are going to have to read the documentation for the commands I recommended -- not because I am a cantankerous type, but because if you want to program, you gotta learn "documentation literacy".

Anyway, so if you add this to what you just posted, you will print out each line in the file:

Code:

char buffer[256] /* put this with your other variables */
     while (fgets(buffer,256,input)) {       /* until fgets() returns NULL at EOF */
           printf("%s",buffer);  
      }
      fclose(input);

Now, to get the individual numbers, you will want to use sscanf() on "buffer" inside the while loop. You can also try using fscanf() to do that, replacing fgets().