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	date.c - sbase - suckless unix tools
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	---
	date.c (1858B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include <ctype.h>
	3 #include <stdio.h>
	4 #include <stdlib.h>
	5 #include <string.h>
	6 #include <time.h>
	7
	8 #include "util.h"
	9
	10 static void
	11 usage(void)
	12 {
	13 eprintf("usage: %s [-u] [-d time] [+format \| mmddHHMM[[CC]yy]]\n…
	14 }
	15
	16 static int
	17 datefield(const char *s, size_t i)
	18 {
	19 if (!isdigit(s[i]) \|\| !isdigit(s[i+1]))
	20 eprintf("invalid date format: %s\n", s);
	21
	22 return (s[i] - '0') * 10 + (s[i+1] - '0');
	23 }
	24
	25 static void
	26 setdate(const char s, struct tm now)
	27 {
	28 struct tm date;
	29 struct timespec ts;
	30
	31 switch (strlen(s)) {
	32 case 8:
	33 date.tm_year = now->tm_year;
	34 break;
	35 case 10:
	36 date.tm_year = datefield(s, 8);
	37 if (date.tm_year < 69)
	38 date.tm_year += 100;
	39 break;
	40 case 12:
	41 date.tm_year = ((datefield(s, 8) - 19) * 100) + datefiel…
	42 break;
	43 default:
	44 eprintf("invalid date format: %s\n", s);
	45 break;
	46 }
	47
	48 date.tm_mon = datefield(s, 0) - 1;
	49 date.tm_mday = datefield(s, 2);
	50 date.tm_hour = datefield(s, 4);
	51 date.tm_min = datefield(s, 6);
	52 date.tm_sec = 0;
	53 date.tm_isdst = -1;
	54
	55 ts.tv_sec = mktime(&date);
	56 if (ts.tv_sec == -1)
	57 eprintf("mktime:");
	58 ts.tv_nsec = 0;
	59
	60 if (clock_settime(CLOCK_REALTIME, &ts) == -1)
	61 eprintf("clock_settime:");
	62 }
	63
	64 int
	65 main(int argc, char *argv[])
	66 {
	67 struct tm *now;
	68 time_t t;
	69 char buf[BUFSIZ], *fmt = "%a %b %e %H:%M:%S %Z %Y";
	70
	71 t = time(NULL);
	72 if (t == -1)
	73 eprintf("time:");
	74
	75 ARGBEGIN {
	76 case 'd':
	77 t = estrtonum(EARGF(usage()), 0, LLONG_MAX);
	78 break;
	79 case 'u':
	80 if (setenv("TZ", "UTC0", 1) < 0)
	81 eprintf("setenv:");
	82 break;
	83 default:
	84 usage();
	85 } ARGEND
	86
	87 if (!(now = localtime(&t)))
	88 eprintf("localtime:");
	89 if (argc) {
	90 if (argc != 1)
	91 usage();
	92 if (argv[0][0] != '+') {
	93 setdate(argv[0], now);
	94 return 0;
	95 }
	96 fmt = &argv[0][1];
	97 }
	98
	99 strftime(buf, sizeof(buf), fmt, now);
	100 puts(buf);
	101
	102 return fshut(stdout, "<stdout>");
	103 }