Example of C variadic macros and some vfprintf wrapping.

printfTS.c

#include <stdio.h>
#include <stdarg.h>
#include <unistd.h>
#include <time.h>

#define printfTS(msg, ...) fprintfTS(stdout, msg, ## __VA_ARGS__)

// This is *not* threadsafe (localtime & strftime)
int fprintfTS(FILE * stream, const char * const msg, ...)
{
   int rc = 0;
   time_t t;
   struct tm *now_p;
   char datetime[20] = "";
   va_list arg;

   time(&t);
   now_p = localtime(&t);
   strftime(datetime, sizeof(datetime), "%H:%M:%S", now_p);
   fprintf(stream, "%s - ", datetime);

   va_start (arg, msg);
   rc = vfprintf(stream, msg, arg);
   va_end(arg);

   return rc;
}

int main()
{
   fprintfTS(stdout, "Some random message #1\n");
   printfTS("Some random message #%d\n", 2);

   return 0;
}

if you need a license, BSDNEW.