How to wait for time to expire - c

Question

I would like to have a function run periodically, given a time step. What is the most efficient way to do this?
I know I could use a while look and just keep checking till the dt period has elapsed. But I'd like to know if there is a better, more efficient/elegant function to use.
I was looking into virtual timers and sigaction. Using this method, I would have the sigaction handler set a flag when the time has elapsed, but I would still need to sit in a while loop checking for that flag to be set in my main function. Alternatively I wonder if I could actually have the handler run the function, but then I would have to pass a lot of arguments, and as far as I have read, handlers don't take arguments, so I would have to use lots of global variables.
What would be the best way to tackled this?

Answer 1

On an *IX'ish system you could
install a handler for SIGALRM, which does nothing
set an alarm using alarm()
call blocking pause()
If the alarm signal is sent pause() will return and
you can run the function in question,
again set the alarm
start over calling pause()
#define _POSIX_SOURCE 1
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
void handler_SIGALRM(int signo)
{
signo = 0; /* Get rid of warning "unused parameter ‘signo’" (in a portable way). */
/* Do nothing. */
}
int main()
{
/* Override SIGALRM's default handler, as the default handler might end the program. */
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = handler_SIGALRM;
if (-1 == sigaction(SIGALRM, &sa, NULL ))
{
perror("sigaction() failed");
exit(EXIT_FAILURE);
}
}
while (1)
{
alarm(2); /* Set alarm to occur in two seconds. */
pause(); /* The call blocks until a signal is received; in theis case typically SIGARLM. */
/* Do what is to be done every 2 seconds. */
}
return EXIT_SUCCESS;
}

Answer 2

The easiest way is to use sleep or usleep as defined in unistd.h.
If neither of those are available then a common workaround is to use a select with a timeout on no file descriptors.

Answer 3

Include time.h and use sleep function like
#include <time.h>
#include <stdio.h>
#include<windows.h>
#include <conio.h>
int main() {
printf("I am going to wait for 4 sec");
Sleep(4000); //sleep for 4000 microsecond= 4 second
printf("Finaaly the wait is over");
getch();
return 0;
}
It will give you a precise delay on microsecond level.
Hope it helped.