Dealing with whitespaces whilst reading a file

[agentsmith]

The aim of my code is to read in a code in a text file and discard comments, i.e. any characters after '#'. So for example, line like this:

main: addi  $3,$0,40   # j  = 40

is transformed into:

main:addi$3,$0,40

I have written a code that does just that. However, if the line only contains a comment I end up with an array of empty characters. Here is my code:

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

#define LEN 60

void comment_remove (char word[LEN])
{
    char temp[LEN];
    int i, j;
    for (i = 0; i < LEN; i++){
        if (word[i] != '#'){
            temp[i] = word[i];
        }else{
            temp[i] = '\0';
        }
    }
    i = 0, j = 0;
    
    while (i < LEN){
        if (temp[i] != ' '){
            word[j] = temp[i];
            i++; 
            j++;
        }else{
            i++;
        }
    }
}

static FILE *open_file (char *file, char *mode) 
{
    FILE *fptr = fopen (file, mode); 

    if (fptr == NULL){			
        perror ("Unable to open file");	
        exit (EXIT_FAILURE);
    }
    return fptr;	
}
    
int main (int argc, char *argv[])
{
    int array_pos = 0;
    char letter, word[LEN];
    FILE *fptr;
    fptr = open_file (argv[1], "r");
    do{
        letter = fgetc (fptr);
        if (letter != '\n'){
            word[array_pos] = letter;
            array_pos++;
        }else{
            word[array_pos] = '\0';
            array_pos = 0;
            comment_remove (word);
            printf ("%s\n", word);
        }
    } while (letter != EOF);
    fclose (fptr);
    return 0;
}

So for example, text file like this:

                       # register allocation:
                       # 
                       # $3 = j
                       # $4 = a = i - 0
                       # $5 = b = i - 1
                       # $6 = c = i - 2
                       # $7 = t1
                       # $8 = t2
                       # $9 = t3

main: addi  $3,$0,40   # j  = 40

comes out like this:

main:addi$3,$0,40

My question is how can I deal with the empty arrays in the beginning of the file?

[vart]

fgetc returns int - so make letter int
Check for EOF before processing the character


why not to read file using fgets line by line, and if th efirst char read is # just skip to reading the next line?