C Initialize a char array of a struct array

Question

I can't understand how I can initialize a char array in an array struct. I have written this code:

typedef struct tomo
{
    char titolo[100];
    char autore[100];
    int anno_pubblicazione;
    float prezzo;
} t_libro;

main(){
    t_libro biblio[2];
    biblio[0] = {"Guida al C", "Fabrizio Ciacchi", 2003, 45.2};
    biblio[1] = {"Harry Potter e la Pietra Filosofale", "J.K.Rowling", 2003, 12.5};
}

but when i compile, it says me that before '{' an expression is expected. How i can solve it? These char arrays give me a lot of problems...

P.S. Ive tried also to use

biblio[0].titolo = "Guida al C";

and in this manner for the other fields of struct, but also in this manner I have an error.

David Heffernan · Accepted Answer · 2014-01-14 16:51:34Z

8

biblio[0] = {"Guida al C", "Fabrizio Ciacchi", 2003, 45.2};

That is not an initialization. That is a simple assignment. You can only use initialization syntax in an initialization. It looks like this:

t_libro biblio[] = {
  {"Guida al C", "Fabrizio Ciacchi", 2003, 45.2},
  {"Harry Potter e la Pietra Filosofale", "J.K.Rowling", 2003, 12.5}
};

Your attempt to write

biblio[0].titolo = "Guida al C";

fails because you cannot assign to character arrays. You must either initialize them, or use a function like strcpy.

Your main declaration is wrong too. It should be

int main(void)

answered Jan 14, 2014 at 16:51

David Heffernan

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4 Comments

ProtoTyPus Over a year ago

I always use main() and it works. Now I try your examples and then I say you if it works or not :)

David Heffernan Over a year ago

It might always work for you on your compiler. But it's wrong.

ProtoTyPus Over a year ago

In my academy has learnt me to make in this manner... =S however your solution works! Thank you very much!

David Heffernan Over a year ago

There is a lot of bad teaching going on. main() might work for your compiler, but it is non-standard. Your teachers should be teaching you int main(void) or int main(int argc, char* argv[]).

Naqued · Accepted Answer · 2017-04-24 15:02:26Z

There is an other solution.

define your char array as a typedef and you could initialize your Array like this.

typedef char T_STRING[100] ;

typedef struct tomo
{
    T_STRING titolo;
    T_STRING autore;
    int anno_pubblicazione;
    float prezzo;
} t_libro;

 t_libro biblio[] = {
  {"Guida al C", "Fabrizio Ciacchi", 2003, 45.2},
  {"Harry Potter e la Pietra Filosofale", "J.K.Rowling", 2003, 12.5}
};

On preprocessing you'r compiler will be able to initialize your array

From the respons of David Hefferman

Your attempt to write

biblio[0].titolo = "Guida al C"; fails because you cannot assign to character arrays. You must either initialize them, or use a function like strcpy.

to explain better, you have to initialize each caractere in the right memory zone.

For example

biblio[0].titolo = "Guida al C"; must be in memory to work good :

biblio[0].titolo[0] = 'G';
biblio[0].titolo[1] = 'u';
biblio[0].titolo[2] = 'i';
biblio[0].titolo[3] = 'd';
biblio[0].titolo[4] = 'a';
biblio[0].titolo[5] = ' ';
biblio[0].titolo[6] = 'a';
biblio[0].titolo[7] = 'l';
biblio[0].titolo[8] = ' ';
biblio[0].titolo[9] = 'C';
biblio[0].titolo[0] = '\0'; // (don't forget to initialize the end of your string)

this is what strcpy (or strncpy) do very well.

Ps : main () { }

gcc will automatically put int main () { } by default

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