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---
title: "Write and read structs to/from files in C"
url: write-and-read-structs-to-files-in-c.html
date: 2024-06-22T16:13:13+02:00
type: note
draft: false
tags: [c]
---
First let's define a shared header file for the struct definition.
```c
// struct.h
typedef struct {
char name[50];
int health;
float damage;
} Character;
```
Now lets write it to a `character.dat` file.
```c
// write.c
#include <stdio.h>
#include <string.h>
#include "struct.h"
int main(void) {
printf("Write struct\n");
Character ch;
strcpy(ch.name, "John Doe");
ch.health = 30;
ch.damage = 5.9;
FILE* file = fopen("character.dat", "wb");
if (file == NULL) {
perror("Error opening file");
return 1;
}
fwrite(&ch, sizeof(Character), 1, file);
fclose(file);
return 0;
}
```
If we check the contents of the `character.dat` file it should look like this.
```txt
$ xxd character.dat
00000000: 4a6f 686e 2044 6f65 0000 0000 0000 0000 John Doe........
00000010: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000030: 0000 0000 1e00 0000 cdcc bc40 ...........@
```
Reading and serializing back to a struct.
```c
// read.c
#include <stdio.h>
#include "struct.h"
int main(void) {
printf("Read struct\n");
Character ch;
FILE* file = fopen("character.dat", "rb");
if (file == NULL) {
perror("Error opening file");
return 1;
}
fread(&ch, sizeof(Character), 1, file);
fclose(file);
printf("Name: %s\n", ch.name);
printf("Health: %d\n", ch.health);
printf("Damage: %.1f\n", ch.damage);
return 0;
}
```
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