int to time_t* type for printing

Question

Reading info from files and printing them out. I save the modification time from stat as an int called mod_time into a struct to recall later. However, when I want to use the ctime()function, I run into a problem because that takes a time_t* type variable. I tried using a typecast but that just resulted in a seg fault. Any help would be much appreciated.

void print(struct file_info **array)
{
    int i;
    for (i = 0; array[i] != NULL; i++)
    {
            printf("%s\n", array[i]->name);
            printf("mod_time: %s\n", ctime((time_t*)array[i]->mod_time));
    }
}

The above is the example with the typecast, which yielded a seg fault. The original one just excluded the (time_t*) typecast, which resulted in a "without a cast" warning.

I don't mind saving the time as `time_t`; what bothers me is having to save it as a pointer, because then I have to deal with a triple line of pointers and I'm already overwhelmed enough as it is with deleting the two iterations of pointers I presently have. If I saved it as a regular `time_t`, how would I turn it into a pointer to be used by `ctime()`? — jiccan, Sep 13 '15 at 05:45
I think you can simply use `&` operator to get a pointer from a variable. example: `&array[i]->mod_time` — MikeCAT, Sep 13 '15 at 05:47

score 2 · Answer 1 · answered Sep 13 '15 at 05:42

Since ctime function takes a pointer to time_t, I think a data of time_t must be on the memory, not only in an expression.

An example of making time_t data on the memory:

void print(struct file_info **array)
{
    int i;
    for (i = 0; array[i] != NULL; i++)
    {
            time_t tmp = (time_t)array[i]->mod_time; /* I'm not sure if this works */
            printf("%s\n", array[i]->name);
            printf("mod_time: %s\n", ctime(&tmp));
    }
}

score 2 · Answer 2 · answered Sep 13 '15 at 05:42

Use of explicit casting in ctime((time_t*)array[i]->mod_time) is not right. You are taking an int and casting it to a pointer. It's not surprising that you get segmentation fault.

It will be better to use time_t for mod_time instead of an int.

If you don't have that option, you can use:

time_t t = array[i]->mod_time;
printf("mod_time: %s\n", ctime(&t));

score 0 · Answer 3 · answered Sep 13 '15 at 07:42

0

Assuming POSIX/C99 or more you could use a compound:

printf("mod_time: %s\n", ctime(&((time_t){array[i]->mod_time})));

answered Sep 13 '15 at 07:42

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int to time_t* type for printing

3 Answers3