comment on

Hello monks.

I'm looking for any standard way to convert a timestamp from one timezone to another inside perl thread.

I have no problem if this happens in main thread, but if I try to change $ENV{TZ} in any other thread, this gives nothing.

Script to demonstrate the problem:

#!/usr/bin/perl

use strict;
use warnings;
use threads;
use POSIX qw(tzset);

my $t=localtime();
print "local time: ",$t,"\n";

my ($tr) = threads->create(\&thr_proc);

$tr->join;

$ENV{TZ}="Europe/Paris";
$t=localtime();
print "main: ",$t,"\n";

$ENV{TZ}="Europe/Moscow";
$t=localtime();
print "main: ",$t,"\n";

sub thr_proc {

    $ENV{TZ} = 'Europe/Paris';
    $t = localtime;
    print "in thread: ",$t,"\n";

    $ENV{TZ} = 'Europe/Moscow';
    $t = localtime;
    print "in thread: ",$t,"\n";
}
[download]

Output:

$ ./mt-demo.pl
local time: Mon Nov 23 15:14:06 2009
in thread: Mon Nov 23 15:14:06 2009
in thread: Mon Nov 23 15:14:06 2009
main: Mon Nov 23 16:14:06 2009
main: Mon Nov 23 18:14:06 2009
[download]

I tried adding of tzset() or some other tricks but with no luck. Here is my perl:

$ perl -V
Summary of my perl5 (revision 5 version 10 subversion 0) configuration
+:
  Platform:
    osname=linux, osvers=2.6.18-128.7.1.el5xen, archname=x86_64-linux-
+thread-multi
    uname='linux testbox-blizzard.didit.com 2.6.18-128.7.1.el5xen #1 s
+mp mon aug 24 09:14:33 edt 2009 x86_64 x86_64 x86_64 gnulinux '
    config_args='-Duseshrplib -Duseithreads -d'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=und
+ef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing
+ -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=6
+4',
    optimize='-O2',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -I
+/usr/local/include'
    ccversion='', gccversion='4.1.2 20080704 (Red Hat 4.1.2-46)', gcco
+sandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+6
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64 /usr/local/l
+ib64
    libs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.5.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.5'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -
+Wl,-rpath,/usr/local/lib/perl5/5.10.0/x86_64-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib'


Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY PERL_DONT_CREATE_GVSV
                        PERL_IMPLICIT_CONTEXT PERL_MALLOC_WRAP USE_64_
+BIT_ALL
                        USE_64_BIT_INT USE_ITHREADS USE_LARGE_FILES
                        USE_PERLIO USE_REENTRANT_API
  Built under linux
  Compiled at Nov 16 2009 16:44:01
  @INC:
    /usr/local/lib/perl5/5.10.0/x86_64-linux-thread-multi
    /usr/local/lib/perl5/5.10.0
    /usr/local/lib/perl5/site_perl/5.10.0/x86_64-linux-thread-multi
    /usr/local/lib/perl5/site_perl/5.10.0
[download]

I'm ready to write some thread-safe TZ manipulation module, but maybe I'm missing something obvious. Thanks.

In reply to Standard way to convert timezone in multithreaded script by whale2

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