Passe back Struct from Void function

Hi!

I have this code and inside the fuction print the correct texto and numbers. Outside the function or in the main no print texto and just print a 2 big numbers.

Inside print "500 dados novos 1000"

Otside print: "2686672 2686728" and no print the texto

Someone help me please?

Thanks

Code:

---

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

struct dados
{
    int largura;
    int velocidade;
    char texto[50];
};

void escreve(struct dados  val);
void ler(struct dados val);

int main()
{

  struct dados entdados;
 
          ler(entdados);
    printf("%s\n",entdados.texto);
    printf("%d\n",entdados.largura);
    printf("%d\n",entdados.velocidade);

    getchar();
    getchar();

    return 0;
}




void ler(struct dados  val)
{

  FILE* fin = fopen("c:\\castanha1.txt", "r");
  fread(&val, sizeof(val), 1, fin);
  fclose(fin);
    printf("%d %s %d\n", val.largura, val.texto, val.velocidade);
  return (void) val;
}

---

You need to pass a pointer to your struct.

Quote:

---

Originally Posted by Salem

You need to pass a pointer to your struct.

---

Can you help me how do this?

Please

Thanks

Code:

---

#include <stdio.h>
#include <stdlib.h>
 
struct dados {
    int largura;
    int velocidade;
    char texto[50];
};
 
void ler(struct dados *val);
 
int main() {
    struct dados entdados;
    ler(&entdados);  // pass the address of the object
    printf("%s\n",entdados.texto);
    printf("%d\n",entdados.largura);
    printf("%d\n",entdados.velocidade);
    return 0;
}

void ler(struct dados *val) { // receive as a pointer
    FILE* fin = fopen("c:\\castanha1.txt", "rb"); // open in binary mode
    if (fin == NULL) {
        perror("fopen");
        exit(EXIT_FAILURE);
    }
    fread(val, sizeof(*val), 1, fin);
    fclose(fin);
    printf("%d %s %d\n", val->largura, val->texto, val->velocidade);
}

---

If the file really is a text file, i.e., if it's contents look something like this (in a text editor) :

Code:

---

1234
56
hello there

---

then don't open it in binary mode and you'll need to read it with fscanf instead of fread:

Code:

---

fscanf(fin, "%d %d %[^\n]", &val->largura, &val->velocidade, val->texto);

---

Quote:

---

Originally Posted by totoco

Can you help me how do this?

Please

Thanks

---

You declare this
void ler(struct dados *val)

You use an & when you call it.

You use -> instead of . to access members inside your function.

That whork fine like i need.

with your help, I understand the pointers and I will study them better.

Thankyou for all.

Hi again!

this code if i rebot the PC work, if i press F9 again does not work.

Someone can help me plese?

Code:

---


#include <stdio.h>
#include <string.h>
struct dados
{
    int largura;
    int velocidade;
    char texto[50];
};
void escreve(struct dados  val);
void ler(struct dados *val);
int main()
{
    struct dados entdados;
    scanf("%[^\n]%*c", entdados.texto);
    entdados.largura=10;
    entdados.velocidade=20;
printf("%d %s %d\n", entdados.largura, entdados.texto, entdados.velocidade);

  //Write text in the file
  escreve(entdados);


    //read text in the file
    ler(&entdados);


    printf("%s\n",entdados.texto);
    printf("%d\n",entdados.largura);
    printf("%d\n",entdados.velocidade);
    return 0;
};

void ler(struct dados *val)  // receive as a pointer
{
    FILE* fin = fopen("c:\\castanha1.txt", "r"); // open in binary mode
    if (!fin)
    {
        printf("Unable to open file!");
        return 1;
    }
    fread(&val, sizeof(*val), 1, fin);
    fclose(fin);
    printf("%d %s %d\n", val->largura, val->texto, val->velocidade);
}



void escreve(struct dados  val)
{
    FILE *ficheiro=fopen("c:\\castanha1.txt","w");
    if (!ficheiro)
    {
        printf("Unable to open file!");
        return 1;
    }
    fwrite(&val, sizeof(val), 1, ficheiro);
    fclose(ficheiro);
}

---

Content of the file after recording:
Attachment 15327

Error after read: (Scanf plus first printf. The print after read does not appear )
Attachment 15328

Look carefully at the lines where you call fread() in the function ler(), and where you call fwrite() in the function escreve().

john.c gives an example of calling fread() in his post:

Code:

---

    fread(val, sizeof(*val), 1, fin);

---

Do you see where his call is different? val is already a pointer, so you don't need the &. Since fread() and fwrite() have similar arguments, you don't need to use & in the other function either.

Quote:

---

Originally Posted by whiteflags

Look carefully at the lines where you call fread() in the function ler(), and where you call fwrite() in the function escreve().

john.c gives an example of calling fread() in his post:

Code:

---

    fread(val, sizeof(*val), 1, fin);

---

Do you see where his call is different? val is already a pointer, so you don't need the &. Since fread() and fwrite() have similar arguments, you don't need to use & in the other function either.

---

Ho Ho!...

It was confusion on my parts.

I was tested and it work fine.

Merry Christmas for all.