Question

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

struct stCrimeArchive {
   char id_student[10];
   int id_document;
   char judgement[30];
   int id_crime;
   char date[12];
   char id_police[12];
};

int main()
{
   struct stCrimeArchive *regi;
   FILE *filea;
   filea = fopen("crimearchives.dat", "r+b");          
   if(!filea) 
 filea = fopen("crimearchives.dat", "w+b");

   int i;
   char num[6];

   regi = (struct stCrimeArchive*)malloc (sizeof(struct stCrimeArchive));

   printf("ID DOCUMENT: ");
   fgets(num, 6, stdin);
   regi->id_document= atoi(num);

   printf("ID STUDENT: ");
   fgets(regi->id_student, 30, stdin);
   for(i = strlen(regi->id_student)-1; i && regi->id_student[i] < ' '; i--)
    regi->id_student[i] = 0;

   printf("CRIME CODE: ");
   fgets(num, 6, stdin);
   regi->id_crime = atoi(num);

   printf("DATE OF THE CRIME: ");
   fgets(regi->date, 30, stdin);
   for(i = strlen(regi->date)-1; i && regi->date[i] < ' '; i--)
    regi->date[i] = 0;   

   printf("ID POLICE: ");
   fgets(regi->id_police, 30, stdin);
   for(i = strlen(regi->id_police)-1; i && regi->id_police[i] < ' '; i--)
    regi->id_police[i] = 0;  

   printf("JUDGEMENT: ");
   fgets(regi->judgement, 30, stdin);
   for(i = strlen(regi->judgement)-1; i && regi->judgement[i] < ' '; i--)
    regi->judgement[i] = 0;     

   fseek(filea, 0, SEEK_END);
   fwrite(&regi, sizeof(struct stCrimeArchive*), 1, filea);

   free(regi);
   fclose(filea);
}  

The context is the following: I am making a variable length file, and on it i’m writing many crime archive with the struct shown above. To do it i need to do a malloc for the struct involved. The problem is when I write it to file, it doesn’t write anything, and I don’t know what mistake(s) I’m doing.

Also I want to read the crime archives from the same file, but I also don’t know what I am doing wrong. Here’s the code for what I am trying to do:

int main()
{ 
   struct stCrimeArchive *regi;
   regi = (struct stCrimeArchive*)malloc (sizeof(struct stCrimeArchive));
   FILE *filea;
   filea = fopen("crimearchives.dat", "r+b");          
   if(!filea) 
    filea = fopen("crimearchives.dat", "w+b");
   rewind(filea);
   while  (fread(&regi, sizeof(struct stCrimeArchive), 1, filea))
    printf("%2d %-11s %-11s %8d %-13s %-14s\n", regi->id_document, regi->id_police, regi->date, regi->id_crime, regi->id_student, regi->judgement);
   fclose(filea);
}

Answer 1

You’ll want to write the size of the struct and not the size of the pointer to the struct.

 fwrite(regi, sizeof(struct stCrimeArchive), 1, filea);

Or maybe this would be more clear:

 fwrite(regi, sizeof(*regi), 1, filea);