CoCalc provides the best real-time collaborative environment for Jupyter Notebooks, LaTeX documents, and SageMath, scalable from individual users to large groups and classes!

1
/*
2
 * Outputs the value of time(2) with the 16 least significant bits zeroed out.
3
 * For use in context keyed payload encoding.
4
 *
5
 * Author: Dimitris Glynos <dimitris at census-labs.com>
6
 */
7

8
#include <stdlib.h>
9
#include <stdio.h>
10
#define __USE_XOPEN
11
#include <time.h>
12

13
char *app = NULL;
14

15
void croak_usage(void)
16
{
17
	fprintf(stderr, "usage: %s [date & time]\n"
18
		"\tSupported date & time format: 'YYYY-MM-DD HH:MM:SS'\n"
19
		"\te.g. %s '2003-11-04 14:23:10'\n",
20
		app, app);
21
	exit(1);
22
}
23

24
time_t parse_time(const char *input)
25
{
26
	struct tm t;
27
	char *p;
28

29
	p = strptime(input, "%Y-%m-%d %H:%M:%S", &t);
30

31
	if ((!p) || (*p != '\0')) {
32
		fprintf(stderr, "error while processing time spec!\n");
33
		croak_usage();
34
	}
35

36
	return mktime(&t);
37
}
38

39
int main(int argc, char *argv[])
40
{
41
	time_t t;
42

43
	app = argv[0];
44

45
	if (argc > 2)
46
		croak_usage();
47

48
	if (argc == 2) 
49
		t = parse_time(argv[1]);
50
	else 
51
		t = time(NULL);
52

53
	printf("%#.8lx\n", t & 0xffff0000);
54
	return 0;
55
}
56

57