Get the Olson TZ name for the local timezone?

Question

How do I get the Olson timezone name (such as Australia/Sydney) corresponding to the value given by C's localtime call?

This is the value overridden via TZ, by symlinking /etc/localtime, or setting a TIMEZONE variable in time-related system configuration files.

Answer 1

This is kind of cheating, I know, but getting from '/etc/localtime' doesn't work for you? Like following:

>>>  import os
>>> '/'.join(os.readlink('/etc/localtime').split('/')[-2:])
'Australia/Sydney'

Hope it helps.

Edit: I liked @A.H.'s idea, in case '/etc/localtime' isn't a symlink. Translating that into Python:

#!/usr/bin/env python

from hashlib import sha224
import os

def get_current_olsonname():
    tzfile = open('/etc/localtime')
    tzfile_digest = sha224(tzfile.read()).hexdigest()
    tzfile.close()

    for root, dirs, filenames in os.walk("/usr/share/zoneinfo/"):
        for filename in filenames:
            fullname = os.path.join(root, filename)
            f = open(fullname)
            digest = sha224(f.read()).hexdigest()
            if digest == tzfile_digest:
                return '/'.join((fullname.split('/'))[-2:])
            f.close()
        return None

if __name__ == '__main__':
    print get_current_olsonname()