%ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl

dda has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks!

Consider the following code:


$ENV{TZ} = "DST";   # something different than current TZ
print localtime();
[download]

The code does not work properly at each invocation. Looks like $ENV{TZ} is cached somewhere. If I add some debug messages, like 'warn "$ENV{TZ}"', before calling localtime(), it works always.

The problem exists only at one of our linux boxes, with perl, v5.8.0 built for i386-linux-thread-multi. Another machines with perl 5.6.1, single-treaded, are not affected.

Probably it is a known issue?

--dda

Comment on %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl Download Code

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Re: %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl by Chmrr (Vicar) on Apr 16, 2003 at 22:35 UTC
This is a problem on the C level, I believe. The `localtime(3)` call does not always check the current value of the TZ environment variable. To force it to do so, POSIX-compliant systems should use the `tzset(3)` call. You can imitate this in perl via: `use POSIX; $\ = "\n"; $ENV{TZ} = "EST"; POSIX::tzset(); print scalar localtime(); $ENV{TZ} = "DST"; POSIX::tzset(); print scalar localtime();` [download] perl -pe '"I lo`+$^X$\"$]!$/"=~m%(.)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'	[reply] [d/l] [select]
Re: Re: %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl by dtr (Scribe) on Jul 23, 2003 at 17:08 UTC
This works fine from a script, but does not work under mod_perl_2! Do you have any suggestions as to how I might go about getting this working under mod_perl_2?????	[reply]
Re: %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl by The Mad Hatter (Priest) on Apr 16, 2003 at 20:23 UTC
I have perl v5.8.0 built for i686-linux-thread-multi-ld and doing `perl -e '$ENV{TZ} = "DST";print scalar localtime(), "\n";'` [download] works fine for me.	[reply] [d/l]
Re: Re: %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl by dda (Friar) on Apr 16, 2003 at 20:31 UTC
Could you please try this: `perl -e '$ENV{TZ} = "EST";print scalar localtime(), "\n";$ENV{TZ} = "DST";print scalar localtime(), "\n";'` [download] It works correctly at 5.6.1 and misbehaves at 5.8.0 --dda	[reply] [d/l]
Re: Re: Re: %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl by Anonymous Monk on Apr 16, 2003 at 20:51 UTC
What dda means to say is: here is the output on a redhat 8, perl 5.8.0 (multithreaded) box (actually we have tried 3 redhat 8 boxes): perl -e '$ENV{TZ} = "EST";print scalar localtime(), "\n";$ENV{TZ} = "DST";print scalar localtime(), "\n";' Wed Apr 16 15:47:41 2003 Wed Apr 16 15:47:41 2003 whereas on a redhat 7.2, perl 5.6.1 box, the output is Wed Apr 16 15:42:25 2003 Wed Apr 16 20:42:25 2003 and on a freebsd box, perl 5.8.0, the output is also correct, i.e. Wed Apr 16 15:42:25 2003 Wed Apr 16 20:42:25 2003 perl 5.6.1 under cygwin seems to manifest the problem also.	[reply]
Re: Re: Re: %ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl by The Mad Hatter (Priest) on Apr 16, 2003 at 21:00 UTC
Hmmmm, I see what you mean. Seems like a bug (like you said). Just to let every know, output is: `Wed Apr 16 15:56:22 2003 Wed Apr 16 15:56:22 2003` [download]	[reply] [d/l]