Problem with const char* in C

Question

I am basically trying to get the time with

struct timeval tv = { };
gettimeofday(&tv, NULL);

And it works. The problem is that the function that is going to accept as an argument the time is of type const char*

So i did

const char *time;
time = &tv.tv_sec;

The problem is, that tv.tv_sec is of type time_t and i need to plug it in

const char *time

to pass it on to the function that needs const char*

How do i do it? Placing an integer into a const char* I've tried some simple ways of casting it, however i am not that experienced with C

Answer 1

When you find yourself needing to cast a time pointer into a char pointer, that is a hint that there is something very wrong. You should take a second look at the problem.

You don't describe the other function that is accepting a const char*, or I would have a better idea of what is happening.

I suspect that you may be required to convert the time integers into a character string and pass a pointer to the beginning of that string. To do that you might want to use a function called strftime.

Answer 2

To format an integer as a string you should use snprintf .

For example:

char resultString[64];

snprintf(resultString, sizeof(resultString), "Current time : %d", tv.tv_sec);

Answer 3

Directly useable C functions are:

• ctime (input is of type time_t )
• asctime (input is of type struct tm )

If you need control over format use:

• strftime (input is of type struct tm )

The linked pages contain examples of use. The string has to be preallocated.

Answer 4

Check sprintf or snprintf .