On 2017-05-09 07:37, Bruno Haible wrote: > Currently, all commands in a Cygwin command window are run with the TZ > environment variable set. > It is set by /etc/profile.d/tzset.sh (or its csh equivalent, > /etc/profile.d/tzset.csh). > Setting TZ is harmful in two ways: > 1) When the user changes the time zone (through the Windows Control Panel) - > for example when traveling - the programs run in the Cygwin command > window will display a stale notion of local time. Only after the user > closes and re-opens a new Cygwin command window, will the programs > display local time according to the new time zone. > 2) It causes native Windows programs (built through mingw, MSVC) to assume > a time zone that is different from the intended one and different from > the one that the user has set in the Windows Control Panel (see APPENDIX > 1 > below). This is because in most geographies, the values of TZ (produced > by winsup/utils/tzset.c and winsup/utils/tzmap.h) contains a slash, and > the tzset() function in the Microsoft CRT does not understand this syntax > - it understands only a different syntax > https://msdn.microsoft.com/en-us/library/90s5c885.aspx . > When TZ is not set, both Cygwin and native Windows programs take their time > zone information from the Windows Control Panel settings. See APPENDIX 2 > below and https://lists.gnu.org/archive/html/bug-gnulib/2017-05/msg00035.html > . > What are the benefits of setting the TZ environment variable? I don't > see any!
Windows TZ is not POSIX compliant: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03 which allows up to TZNAME_MAX bytes from the portable character set in the current locale and quoting using <> which allows alphanumeric, plus, and minus characters from that set, e.g. TZ=<MSK+3>-6 instead of Asia/Omsk: $ TZ='<MSK+3>-6' date -d2017-01-01 +%Z%z MSK+3+0600 $ TZ=Asia/Omsk date -d2017-01-01 +%Z%z +06+0600 $ TZ='<MSK+3>-6' date -d2017-07-01 +%Z%z MSK+3+0600 $ TZ=Asia/Omsk date -d2017-07-01 +%Z%z +06+0600 Now they have quoting, maybe they will consider allowing other characters from the current locale e.g. UTF-8 <МСК+3>, which works with Cygwin: $ TZ='<МСК+3>-6' date -d2017-01-01 +%Z%z МСК+3+0600 $ TZ='<МСК+3>-6' date -d2017-01-01 +%Z%z | cat -A M-PM-^\M-PM-!M-PM-^Z+3+0600$ -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
