tzname doesn't always get set. Assuming it's meant to be
POSIX-compliant (not necessarily XSI/SUS here, but POSIX) then the
following behavior is buggy:
Doing the following:
export TZ=CAT0
cat > daytime.c <<EOF
#include <stdio.h>
#include <time.h>
int main(void)
{
tzset();
printf("tzname[0]: %s\n", tzname[0]);
printf("tzname[1]: %s\n", tzname[1]);
/*
printf("daylight: %d\n", daylight);
printf("timezone: %ld\n", timezone);
*/
}
EOF
cc daytime.c
./a.out
The following is the output:
tzname[0]:
tzname[1]:
nota bene: both of those aren't null/empty, they're three spaces.
This is incorrect, as CAT0 is a valid value of TZ. If we set it to
CAT0DOG0 instead, the output changes dramatically:
tzname[0]: CAT
tzname[1]: DOG
This is the expected output for when TZ is CAT0DOG0.
Back to TZ just being CAT0, a friend using GNU/Linux was able to show
me the output there:
tzname[0]: CAT
tzname[1]: CAT
If I read POSIX correctly, GNU's implementation and output are correct
here. This is the output I expect.
I found FreeBSD's output was also buggy, in a different way:
tzname[0]: EST
tzname[1]:
I'll be sending them a bug report too.
References:
https://man.openbsd.org/ctime.3
https://pubs.opengroup.org/onlinepubs/9699919799/functions/tzset.html
