Node:Initializing structures, Previous:Pointers to structures, Up:struct

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Initializing structures

In the chapter on arrays, we explored how to initialize an array with values at compile time. (See Initializing arrays.) It is also possible to initialize structures at compile time, as shown below. (This code example also shows how to dynamically allocate structures with malloc and initialize them with the -> operator. See Memory allocation, for more information on this technique.)

#include <stdio.h>

/* To shorten example, not using argp */
int main()
{
  struct personal_data
  {
    char name[100];
    char address[200];
    int year_of_birth;
    int month_of_birth;
    int day_of_birth;
  };

  struct personal_data person1 =
  {
    "Liddell, Alice",
    "Wonderland",
    1852,
    5,
    4
  };

  struct personal_data person2 =
  {
    "Hale-Evans, Ron",
    "Seattle, Washington",
    1965,
    6,
    27
  };

  struct personal_data* person_ptr1;
  struct personal_data* person_ptr2;

  person_ptr1 = (struct personal_data*)
    malloc (sizeof (struct personal_data));

  strcpy (person_ptr1->name, "Adams, Douglas");
  strcpy (person_ptr1->address, "The Galaxy");
  person_ptr1->year_of_birth = 1952;
  person_ptr1->month_of_birth = 3;
  /* Don't know his exact birthday */

  person_ptr2 = (struct personal_data*)
    malloc (sizeof (struct personal_data));

  strcpy (person_ptr2->name, "Egan, Greg");
  strcpy (person_ptr2->address, "Permutation City");
  person_ptr2->year_of_birth = 1961;
  /* Don't know his birthday */

  puts ("Data contained:");
  puts (person1.name);
  puts (person2.name);
  puts (person_ptr1->name);
  puts (person_ptr2->name);

  return 0;
}

Any trailing items not initialized by data you specify are set to zero.