[erlang-questions] Setting TZ variable

[Alain O'Dea]

On Thursday, December 2, 2010, Alexey Romanov
<alexey.v.romanov@REDACTED> wrote:
> On Thu, Dec 2, 2010 at 8:13 PM, Alain O'Dea <alain.odea@REDACTED> wrote:
>> Out of curiosity, do you need to change the timezone at runtime?
>
> Yes. The requirement probably could be worked around (e.g. by
> restarting the system when the timezone changes) but it would be
> better if I can avoid this.
>
>> Otherwise the shell shook be fine.  I use the shell approach to force
>> Zotonic into EST.
>>
>> If you need runtime timezone handling I recommend using GMT and
>> putting in a dispay module to convert to the timezone needed by the
>> current process.  Otherwise you could get strange behavior when otwo
>> process change the global timezone and get muddled in context
>> switching.
>
> Ah no, I need precisely to handle actual timezone change (the system
> only finds at runtime what timezone it's in by asking a server...)

This sounds like a one-time or synchronized operation so I see no
issue with os:setenv("TZ",...) for that :)

>
>> On Thursday, December 2, 2010, Alexey Romanov
>> <alexey.v.romanov@REDACTED> wrote:
>>> I've tried to follow the advice given by Ulf Wiger in this old thread:
>>> http://www.erlang.org/pipermail/erlang-questions/2006-December/024291.html
>>>
>>> However, it doesn't work for me:
>>>
>>> aromanov@REDACTED:~/workspace/gmcontroller$ erl
>>> Erlang R14B (erts-5.8.1) [source] [smp:2:2] [rq:2] [async-threads:0]
>>> [hipe] [kernel-poll:false]
>>>
>>> Eshell V5.8.1  (abort with ^G)
>>> 1> os:getenv("TZ").
>>> false
>>> 2> time().
>>> {17,49,40}
>>> 3> os:putenv("TZ", "GMT").
>>> true
>>> 4> os:getenv("TZ").
>>> "GMT"
>>> 5> time().
>>> {17,50,8}
>>>
>>> Am I doing something wrong?
>>>
>>> Setting TZ in the shell does work (but isn't suitable for my purposes):
>>>
>>> aromanov@REDACTED:~/workspace/gmcontroller$ TZ=GMT erl
>>> Erlang R14B (erts-5.8.1) [source] [smp:2:2] [rq:2] [async-threads:0]
>>> [hipe] [kernel-poll:false]
>>>
>>> Eshell V5.8.1  (abort with ^G)
>>> 1> os:getenv("TZ").
>>> "GMT"
>>> 2> time().
>>> {14,50,39}
>>>
>>> Yours, Alexey Romanov
>>>
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>>>
>>
>
>
>
> --
> Yours, Alexey Romanov
>