Question

I need to put a string (from a file) in a matrix and print out the result. I have some issue in understanding the right way to do this so:

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

int main (int argc, char *argv[])
{
    const int MAX = 50;
    char mat[MAX][MAX];
    char str[MAX];
    char word[MAX];
    int row = 0;
    int i = 0;

    FILE * fp;

    fp = fopen ("file.txt", "r");

    if (fp == NULL)
        printf ("Error!\n");

    while (fgets(str, MAX, fp) != NULL)
    {
        sscanf (str, "%s\n", word);

        strcpy(mat[i][0], word);

        row++;
    }

    for (i = 0; i <= row; i++)
    {
            puts(mat[i][0]);
    }

    return 0;
}

I’m obliviously doing something wrong but… what?

I have a file like this:

One
Two
Three
Four
Five
Six
Hello

Answer 1

If you compile this with gcc, it will give you two warnings: each warning points to one of the three major errors in the code:

main.c: In function 'main':
main.c:24: warning: passing argument 1 of 'strcpy' makes pointer from integer without a cast
main.c:31: warning: passing argument 1 of 'puts' makes pointer from integer without a cast

Each of those line numbers — 24 and 31 — is a line where you’re using mat[i][0], which is a character, when you should instead use mat[i], which is a character array. Fix those, and then there’s just one problem: you use i, which is always 0, in the while loop. Use row, which is incremented as the row progresses, and the program should work exactly as designed.

There are a couple of other things I would change to improve the program: your while loop reads a string into one buffer, copies it into a second buffer, then copies it into the matrix; you could just scan it directly into the matrix and be done with it!