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Subject Author Date
global variables in threaded perl programs iloveperl 04-12-2008
Posted by iloveperl on April 12, 2008, 8:23 pm
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 Hi,

I am thinking of writing a new script as a multi threaded
program. This is my first threaded program.
I wrote a small program to understand how
to share global variables in all threads.

use warnings;
use strict ;
use threads ;
use vars qw($sub1 $sub2) ;
$sub1 = 0 ;
$sub2 = 0 ;
my $thr1 = threads->new(\&sub1);
my $thr2 = threads->new(\&sub2);
sleep(10);
print "current $sub1 $sub2..\n" ;
sub sub1() {
$sub1 = 1000 ;
print "$sub1\n" ;
}
sub sub2() {
$sub2 = 2000 ;
print "$sub2\n" ;
}


In the above code it starts two threads in which global variables are
set to a value.
output of the program

1000
2000
current 0 0..

why does the last print line does not take the value of 1000 or 2000.

thanks.

print "current $sub1 $sub2..\n" ;
it does not print 1000 and 2000. rather it


Posted by Joost Diepenmaat on April 12, 2008, 8:28 pm
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 iloveperl@abc.com writes:

> In the above code it starts two threads in which global variables are

> set to a value.
> output of the program
>
> 1000
> 2000
> current 0 0..
>
> why does the last print line does not take the value of 1000 or 2000.

Because no variables are shared by default. See perldoc threads::shared

--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/

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