Why pointer to structure element is not working on sscanf?

Question

I need help with a C function I'm trying to do:

#define MAXLEN 128
typedef struct
{
    char *title;
    char *autor;
    int year;
    int num_sh;
    char *sec_sh;
    int flooor;
    char *building;
    char *city;
} book;

void csvToStruct(char *line, book *pBook)
{
    char sec_sh[MAXLEN], title[MAXLEN], autor[MAXLEN], building[MAXLEN], city[MAXLEN];
    int year, num_sh, flooor;
    sscanf(line, "\"%[^\"]\",\"%[^\"]\",%d,%d,\"%[^\"]\",%d,\"%[^\"]\",\"%[^\"]\"",
           title, autor, &year, &num_sh, sec_sh, &flooor, building, city);

    pBook->title = title;
    pBook->autor = autor;
    pBook->year = year;
    pBook->num_sh = num_sh;
    pBook->sec_sh = sec_sh;
    pBook->flooor = flooor;
    pBook->building = building;
    pBook->city = city;
}

I was trying to, instead of asigning my strucure elements values using pBook->element=value, putting pBook->element directly into sscanf. But it isn't working. Why it doesn't work? In my main function, I'm calling csvToStruct in the following way:

int main(void)
{
    book newBook = (book*)malloc(sizeof(book));
    csvToStruct(line, newBook);
};

The line variable is of type char * that I'm getting from a csv file using fgets() function.

Answer 1

I am going to guess what you old code looked like (its frustrating when you say - "I tried changing this code to something else and it didnt work", but dont show that code you tried).

Anyway you did this (simplifying to one field)

      sscanf(line, "%s",pBook->title);

this doesnt work becuase pbook->title doesnt point to any valid memory to store the data in.

You can do a few things

Reserve space in the book struct

typedef struct
{
    char title[MAXLEN];

} book;

Or you can allocate some heap memory of the correct size so as not to be so wasteful., sadly that is not doable in a one liner because we need to know how big it is.

This is what you must do (your old code was wrong too and will be fixed the same)

 sscanf(line, "%s", title);
 pBook->title = strdup(title);

strdup will allocate memory of the correct size and copy the string into it for you.

Note that you old code was wrong too, becuaseyou set pBook->title to point to stack memory in this function. That memory is released once this function returns.