how to get a dynamic array using struct in c

Question

In the code below I have my cars array set to max length of 10000, but what should I do if I want to set the array size to a number that the user will input?

#define MAX 10000

typedef struct Car{
    char model[20];
    char numberCode[20];
    float weight, height, width, length;
}cars[MAX];

Do you know how to use malloc and free for the primitive types like int? Then you know how to dynamically allocate memory for a structure as well. — Some programmer dude
– Some programmer dude, Commented Jun 29, 2015 at 5:20
I'm currently studying how to use them. But they seem complicated to me. — Gianlucca
– Gianlucca, Commented Jun 29, 2015 at 5:21
This will probably make a type definition of an array instead of creating an array of objects. — Raman
– Raman, Commented Jun 29, 2015 at 5:24

Spikatrix · Accepted Answer · 2015-06-29 05:31:08Z

6

#include <stdlib.h> /*Header for using malloc and free*/

typedef struct Car{
    char model[20];
    char numberCode[20];
    float weight, height, width, lenght;
} Car_t;
/*^^^^^^ <-- Type name */

Car_t *pCars = malloc(numOfCars * sizeof(Car_t));
/*                       ^            ^         */
/*                      count     size of object*/
if(pCars) {
  /* Use pCars[0], pCars[1] ... pCars[numOfCars - 1] */
  ...
} else {
  /* Memory allocation failed. */
}
...
free(pCars); /* Dont forget to free at last to avoid memory leaks */

When you write:

typedef struct Car{
  ...
}cars[MAX];

cars is a type which is a composite type containing MAX cars and possibly this is not something you want.

edited Jun 29, 2015 at 5:31

Spikatrix

20.3k7 gold badges44 silver badges85 bronze badges

answered Jun 29, 2015 at 5:23

Mohit Jain

30.6k8 gold badges80 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Raman · Accepted Answer · 2015-06-29 05:35:42Z

1

First of all use typedef like this

typedef struct Car
{
   char model[20];
   char numberCode[20];
   float weight, height, width, lenght;
}car_type;

Then in main() you go like this:

 main()
 {
    ...
   int n;
   scanf("%d",&n);
   car_type *cars =(car_type *) malloc(n*sizeof(car_type));
    ...  
 }

answered Jun 29, 2015 at 5:35

Raman

2,8052 gold badges31 silver badges48 bronze badges

Collectives™ on Stack Overflow

how to get a dynamic array using struct in c

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related