How do I create a dynamic array of struct pointers?

Question

I need to read in some data from a csv file, and store each component into a struct.

The csv file has the following headers: name, last name, phone number, age

The csv file has an unknown number of records, and I want to create a dynamic array of pointers to structs to store this data.

I started with this:

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

int main(int argc, char **argv){
    typedef struct{
    char** name; 
    char** last_name; 
    int * number;
    int* age}person_t;

    person_t **storage;


}

But now I am absolutely stuck and have no idea how to proceed. Please help!

Does this answer your question? [Allocating memory for a Structure in C](https://stackoverflow.com/questions/2177391/allocating-memory-for-a-structure-in-c) — Mark Benningfield, Aug 20 '21 at 15:43
Or this [one](https://stackoverflow.com/questions/19613752/how-to-properly-malloc-for-array-of-struct-in-c) — Mark Benningfield, Aug 20 '21 at 15:44
@MarkBenningfield I understand how to do that, I'm confused about how to create an array of struct pointers — Aquila, Aug 20 '21 at 15:44
Not necessarily the question you asked about, but: you've got a bunch of unnecessary extra pointer levels in your `person_t` type. You want `int age`, not `int *age`. You might want `char *name` and `char *last_name`, but those will require allocation, too, so for a start maybe go with `char name[10]` and `char last_name[20]`. Not sure about the phone number. — Steve Summit, Aug 20 '21 at 15:50
You need to decide whether you want an array of pointers to your structures, or just an array of your structures. The simpler array of structures will be easier at first, which will be `person_t *storage`. — Steve Summit, Aug 20 '21 at 15:54

score 0 · Answer 1 · answered Aug 20 '21 at 16:24

You probably want something like this:

typedef struct{
  char name[20];        // can store names of maximum length 19
  char last_name[20];   // can store last names of maximum length 19
  int number;
  int age
} person_t;


int main(int argc, char **argv){
  person_t **storage;
  ...
  // allocate an array of nbOfElements pointers to person_t
  storage = malloc(nbOfElements * sizeof(person_t*));

  for (int i = 0; i < nbOfElements; i++)
  {
     ...
     ... read one CSV line 
     ...
     // allocate memory for one person_t and store the pointer
     storage[i] = malloc(sizeof(person_t));
   
     // fill the structure
     strcpy(storage[i]->name, ...);
     strcpy(storage[i]->last_name, ...);
     storage[i]->number = ...
     storage[i]->age = ...;
  }        
}

This is not complete code, just an outline of what you could do. Also there are no error checks for malloc for brevity.

And the OP said "The csv file has an unknown number of records", so pretty soon there'll be an opportunity to learn about `realloc`. — Steve Summit, Aug 20 '21 at 17:58

How do I create a dynamic array of struct pointers?

1 Answers1