Question

How to write and read an array of structs to and from a binary file in C

Answer 1

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

#define SIZE 3

struct user {
    char name[16];
    int age;
} vip[SIZE] = {
              {"dan", 43},
              {"ben", 51},
              {"tom", 62}
};


int main()
{
    char filename[16] = "d:\\data.bin";

    // write
    FILE* fp = fopen(filename, "wb");
    if (!fp) {
        printf("Unable to open file");
        return 1;
    }

    for (int i = 0; i < SIZE; i++) {
        fwrite(&vip[i], sizeof(struct user), 1, fp);
    }

    fclose(fp);

    // read
    fp = fopen(filename, "rb");
    if (!fp) {
        printf("Unable to open file");
        return 1;
    }

    struct user u;
    for (int i = 0; i < SIZE; i++) {
        fread(&u, sizeof(struct user), 1, fp);
        printf("%s %d\n", u.name, u.age);
    }

    return 0;
}



/*
run:

dan 43
ben 51
tom 62

*/

 

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