Thread: I cant find what is wrong with this code

This program is to read record from a file and then validate
the 5th element str[5].
From the valid check digits out of 45 recs only 5 is reported
valid. I dont know what is wrong with this code

Example of rec on file is c12543256 my name where i leave......\n
please help, am i reading the record wrongly?

Code:

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

    char str[107];
    char temp[5], chk_digit, *c_ptr;
    int  weights[] = {5, 4, 3, 2}, *w_ptr;
    int  total=0, value, rem, check_num;

   while(fgets(str,sizeof(str), fp) != NULL)
     {
   w_ptr = weights;
     strncpy(temp,&str[1],4);

   for(c_ptr=temp; *c_ptr; c_ptr++)
      {
       value = *c_ptr - '0';
       total += value * *w_ptr++;
         }

         rem = total % MODULUS;
         check_num = MODULUS - rem;
      if( check_num < 10 )
       chk_digit = check_num + '0';
        else
         if( check_num == 10 )
          chk_digit = '0';
           else
            chk_digit = 'X';

       if(chk_digit != str[5])
       {
       fprintf(prn_ptr,"\nError in code");
         }
      else
      fputs(str,fv);
        }

      fprintf(prn_ptr,"\f");
            }

thanks