Array of structs in C

Question

I'm trying to create an array of structs and also a pointer to that array. I don't know how large the array is going to be, so it should be dynamic. My struct would look something like this:

typedef struct _stats_t
{
 int hours[24]; int numPostsInHour;
 int days[7]; int numPostsInDay;
 int weeks[20]; int numPostsInWeek;
 int totNumLinesInPosts;
 int numPostsAnalyzed;

} stats_t;

... and I need to have multiple of these structs for each file (unknown amount) that I will analyze. I'm not sure how to do this. I don't like the following approach because of the limit of the size of the array:

# define MAX 10
typedef struct _stats_t
{
 int hours[24]; int numPostsInHour;
 int days[7]; int numPostsInDay;
 int weeks[20]; int numPostsInWeek;
 int totNumLinesInPosts;
 int numPostsAnalyzed;

} stats_t[MAX];

So how would I create this array? Also, would a pointer to this array would look something this?

stats_t stats[];
stats_t *statsPtr = &stats[0];

Questions: Can you manage a dynamic array of int? Can you manage a static array of struct? If there answer to either of these questions is "No.", I'd suggest working on that first. Once you can manage both of those, the answer to this should be obvious. Finally, you can find help on both of the above on Stack Overflow already. — dmckee --- ex-moderator kitten
The _t suffix is reserved for system headers. Don't use it. — Nicholas Shanks

wallyk wallyk · Accepted Answer · 2010-04-04T21:20:09

This is how it is usually done:

size_t n = <number of elements needed>
stats_t *ptr = malloc (n * sizeof (stats_t));

Then, to fill it in,

for (size_t j = 0;  j < n;  ++j)
{
   ptr [j] .hours = whatever
   ptr [j] .days = whatever
   ...
}

Array of structs in C

5 Answers