Question

i want to read text file containing the data of 4X4 matrix each element is separated by a space and it is divided into 4 rows which represent the matrix. it is in Following form

1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

now i came across the code that

 static const char filename[] = "file.txt";
   FILE *file = fopen ( filename, "r" );
   if ( file != NULL )
   {
      char line [ 128 ]; /* or other suitable maximum line size */

      while ( fgets ( line, sizeof line, file ) != NULL ) /* read a line */
      {
         fputs ( line, stdout ); /* write the line */
      }
      fclose ( file );
   }
   else
   {
      perror ( filename ); /* why didn't the file open? */
   }
   return 0;

which reads the file but i want to know that how to read them element wise so that i can store them in 2D array

Answer 1

fscanf to the rescue:

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

int main()
{
    FILE* file = fopen("input.txt", "r");
    if (!file)
        perror("Can't open input");

    int matrix[4][4] = {
        { 0, 0, 0, 0, },
        { 0, 0, 0, 0, },
        { 0, 0, 0, 0, },
        { 0, 0, 0, 0, },
    };

    int i;
    for (i=0; i<4; i++)
    {
        int n = fscanf(file, "%i %i %i %i", &matrix[i][0], 
                &matrix[i][1],
                &matrix[i][2],
                &matrix[i][3]);
        if (n != 4) {
            if (errno != 0)
                perror("scanf");
            else 
                fprintf(stderr, "No matching characters\n");
        }
    }

    for (i=0; i<4; i++)
        printf("%i %i %i %i\n", matrix[i][0], 
                matrix[i][1],
                matrix[i][2],
                matrix[i][3]);
}

Of course you need to make the code more generic