/*
 * Copyright (c) 2023 Mitchell Riedstra
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 *
 * A fairly basic interface to `strftime`, since dates are apparently difficult
 * to handle with regular command line utilites and the POSIX spec for `date`
 * is rather lacking.
 */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <errno.h>


void
help()
{
	puts("strftime <fmt> [timestamp]");
	exit(1);
}

int
main(int argc, char **argv) {
	time_t t = time(NULL);
	char **a = argv+1;
	struct tm *tm;
	char *fmt;
	char out[256] = {0};

	if (!*a) {
		help();
	}

	fmt = *a;
	a++;

	if (*a) {
		errno = 0;
		t = strtol(*a, NULL, 10);
		if (errno != 0) {
			perror("strtol");
			exit(1);
		}
	}

	tm = localtime(&t);

	if (strftime(out, 256, fmt, tm) == 0) {
		perror("strftime");
		exit(1);
	}

	puts(out);
}