Question

How to read struct from binary file in C

Answer 1

#include <stdio.h>

typedef struct Point {
    int x, y;
} Point;
 
int main(void) {
	Point p;
    
    FILE* in = fopen("data.bin", "rb");
	
    if (in == NULL) {
        return 1;
    }
    
    size_t total_read = fread(&p, sizeof(Point), 1, in);
    fclose(in);
    if (total_read == 0) {
        return 2;
    }
    
    printf("%d, %d\n", p.x, p.y);
 
    return 0;
}

 

 
 
/*
run:
 
89731, 26
   
*/

 

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Answer 2

// A c program that read a struct from binary file 
 
#include <stdio.h>
  
struct Numbers {
   int n1, n2;
};
 
int main(void)
{
    struct Numbers N;
    FILE *fp;
 
    if ((fp = fopen("d:\\data.bin", "rb")) == NULL) {
        printf("Error open file");
        return 1;
    }
 
    for (int i = 1; i <= 3; i++) {
        fread(&N, sizeof(struct Numbers), 1, fp); 
        printf("n1 = %d n2 = %d\n", N.n1, N.n2);
    }
     
    fclose(fp); 
  
    return 0;
}
 
 
   
/*
run:
 
n1 = 1 n2 = 2
n1 = 2 n2 = 3
n1 = 3 n2 = 4
 
*/

 

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