Re^2: FileHandles and threads

[zentara]

Thanks for that code example! Passing a filehandle through a thread shared variable was something I've been searching for for awhile. Just for demonstration purposes, it can go the other way too.....create the filehandle in the thread, and read it in main.

#!/usr/bin/perl
use warnings;
use strict;
use threads;
use threads::shared;

my %shash;
#share(%shash); #will work only for first level keys 
my %hash;

 share ($shash{'go'});
 share ($shash{'fileno'});
 share ($shash{'pid'});
 share ($shash{'die'});

 $shash{'go'} = 0;
 $shash{'fileno'} = -1;
 $shash{'pid'} = -1;
 $shash{'die'} = 0;

 $hash{'thread'} = threads->new(\&work);

 $shash{'go'} = 1;

sleep 1;  # cheap hack to allow thread to setup 

my $fileno = $shash{'fileno'};
open (my $fh, "<&=$fileno") or warn "$!\n";

while ( <$fh> ){ print "In main-> $_";  }

#wait for keypress to keep main thread alive 
<>;

# control-c to exit

################################################################## 
sub work{
    $|++;
    while(1){
       if($shash{'die'} == 1){ goto END };

       if ( $shash{'go'} == 1 ){

        my $pid = open(FH, "top -b |" ) or warn "$!\n";
        my $fileno = fileno(FH);
        print "fileno->$fileno\n";
        $shash{'fileno'} = $fileno;

    $shash{'go'} = 0; #turn off self before returning       
       }else
         { sleep 1 }
    }
END:
}
#####################################################################

[BrowserUk]

I first played with this a couple of years ago. I first mentioned it here about a year ago in Re^3: Passing globs between threads.

By using a pool of threads and passing the filenos via a queue, it is possible to efficiently emulate all the usual forms of forking server architecture.