#include <unistd.h>		// symbolic constants
#include <stdlib.h>		// general utilities
#include <stdio.h>		// printf
#include <sys/time.h>		// gettimeofday, gethrtime
#include <sys/utsname.h>	// uname

//
// Purpose:	Measure the average execution time of the uname(2)
//		system call and the stub function call using gethrtime(3C) or
//		gettimeofday(3C) depending on the OS.  Run each case 3 times.
//
// Usage:	timeit > timeit.out			# produce raw data
//		timeit.sh < timeit.out > timeit.txt	# beautify output
//
// Build:	g++ -o timeit timeit.c
//

const int LIMIT = 1000000;			// limit on N

void stub (void) {	/* null function */ 	}

int
main (int argc, char *argv[]) {

  char	which[2] = { 'f', 's' };

  for (int i=0; i<2; i++) {		// each call type
    for (int N=10; N<=LIMIT; N*=10) {		// N = 10, 100, ... , LIMIT
      double	tavg;

      for (int j=0; j<3; j++) {		// do 3 times
	int64_t	tbegin, tend;		// in nanoseconds
	char	tag;

	if (which[i] == 'f') {
	  for (int k=0; k<N; k++) { stub(); }
	} else {
	  for (int k=0; k<N; k++) { uname(&x); }
	}
	printf ("%c\t%7d\t%f\t%lld\t%lld\t%lld\n",
			which[i], N, tavg/1000, tbegin, tend, (tend-tbegin));
      }
    }
  }

  return 0;
}