Hi,
I can't figure out from the man pages why
mktime() is giving a different result than date -f.
Both strptime and mktime are supposed to use the
local timezone, as does date.
The output of date is correct; mktime() is an hour later.
What am I missing here?
Thanks,
m
$ uname -s; uname -r
FreeBSD
6.0-RELEASE-p9
$ gcc test.c
$ ./a.out
date -j -f "%Y-%m-%d %H:%M:%S" "2008-10-14 08:06:21" +%s returns 1223985981
a.out: tm.tm_sec= 21
a.out: tm.tm_min= 6
a.out: tm.tm_hour = 8
a.out: tm.tm_mday = 14
a.out: tm.tm_mon= 9
a.out: tm.tm_year = 108
a.out: tm.tm_wday = 0
a.out: tm.tm_yday = 0
a.out: tm.tm_isdst = 0
a.out: tm.tm_zone = (null)
a.out: tm.tm_gmtoff = 0
exp 1223985981, got 1223989581: delta = -3600
$ date -j -r 1223985981
Tue Oct 14 08:06:21 EDT 2008
$ date -j -r 1223989581
Tue Oct 14 09:06:21 EDT 2008
$ cat test.c
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define EXITOK(rc) (WIFEXITED(rc) && WEXITSTATUS(rc) == 0)
static char *time_s = "2008-10-14 08:06:21";
static char *fmt= "%Y-%m-%d %H:%M:%S";
/* Return seconds since epoch computed from date utility. */
time_t
expected()
{
char cmd[500] = {0};
char outbuf[4096];
unsigned longexp, act;
int rc;
FILE*pfp;
/* date -j -f "%Y-%m-%d %H:%M:%S" "2008-10-14 08:06:21" +%s */
(void) snprintf(cmd, sizeof(cmd),
"date -j -f \"%s\" \"%s\" +%%s", fmt, time_s);
if ((pfp = popen(cmd, "r")) == NULL)
errx(1, "popen failed.");
while (fgets(outbuf, sizeof(outbuf), pfp) != NULL)
printf("%s returns %s", cmd, outbuf);
if((rc = pclose(pfp)) == -1)
errx(1, "pclose returns -1");
if (!EXITOK(rc))
errx(1, "%s didn't terminate normally", cmd);
return (time_t) strtoul(outbuf, 0, 10);
}
/* Returns seconds since epoch using strptime() and mktime() */
time_t
actual()
{
struct tm tm;
time_t rval;
rval = (time_t) 0;
memset(&tm, 0, sizeof(tm));
if (strptime(time_s, fmt, &tm) == NULL)
errx(1, "fmt '%s' didn't match '%s'", fmt, time_s);
warnx("tm.tm_sec= %d", tm.tm_sec);
warnx("tm.tm_min= %d", tm.tm_min);
warnx("tm.tm_hour = %d", tm.tm_hour);
warnx("tm.tm_mday = %d", tm.tm_mday);
warnx("tm.tm_mon= %d", tm.tm_mon);
warnx("tm.tm_year = %d", tm.tm_year);
warnx("tm.tm_wday = %d", tm.tm_wday);
warnx("tm.tm_yday = %d", tm.tm_yday);
warnx("tm.tm_isdst = %d", tm.tm_isdst);
warnx("tm.tm_zone = %s", tm.tm_zone);
warnx("tm.tm_gmtoff = %lu", tm.tm_gmtoff);
return mktime(&tm);
}
int
main(void)
{
time_t act, exp;
double delta;
exp = expected();
act = actual();
delta = difftime(exp, act);
if (fabs(delta) > DBL_EPSILON) {
printf("exp %llu, got %llu: delta = %.0f\n",
(long long int) exp, (long long int) act,
delta);
return 1;
}
else
return 0;
}
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