Trying to write a code in which output should be display text after a delay of 2 seconds using Interval Timer

#include<stdio.h>
#include <time.h>
int main ()
{enter code here
time_t now;
struct tm timespace;
double seconds;
struct timespec t = { 2/*seconds*/, 0/*nanoseconds*/};
while (1){
time(&now); 
seconds=now;
printf ("%.f Timer Counter\n", seconds);
timespace = *localtime(&now);
nanosleep(&t,NULL);
time(&now);
seconds=now;
fflush(stdout); 
printf ("%.f Counter Value After two second delay.\n Hellow.\n", seconds);
seconds=now;
printf("\n\n\n");
timespace = *localtime(&now);
nanosleep(&t,NULL);
fflush(stdout); 

time(&now); 
seconds=now;
printf ("%.f Counter Value After two second delay.\n Hello World 2.\n", seconds);
return 0;
}
}

every time i compile this code it says

variable `timespec t' has initializer but incomplete type

and

'nanosleep' undeclared (first use this function)