Hi again, I figured out a way with pipes. It uses IO::Pipe and is a bit tricky, because you need to pass the IO::Pipe object to the thread, before you call writer or reader on it. Otherwise IO::Pipe throws an error about IO::Pipe::End. But this works as proof of concept. It does not have any disk files involved to avoid the fileno problem. Also, since I detached the threads, you need to hit control-c to exit, or work out a method of detecting when all threads are finished, probably thru a shared variable. 
#!/usr/bin/perl
use warnings; 
use strict;
use threads;
use IO::Select;
use IO::Pipe;

my @ranges = ( [1,10000000],[10000001,20000000],[20000001,30000000],
               [30000001,40000000],[40000001,50000000] );

my $sel = new IO::Select();

# thread launching

foreach (@ranges){

    my $pipe = IO::Pipe->new();
    my $start = $_->[0];
    my $end = $_->[1];
    print "$start $end $pipe\n";

  threads->create( \&thread, $start, $end, $pipe )->detach;

  # only call reader after pipe has been passed to thread  
  $sel->add( $pipe->reader() );
}

# watching thread output
print "Watching\n\n";

while(1){     
     
     foreach my $h ($sel->can_read){
         my $buf;
         if ( (sysread($h, $buf, 1024) > 0 ) ){ 
           print "Main says: $buf\n"; 
         }
     }
}


sub thread{

my( $start, $finish, $pipe ) = @_;

my $wh = $pipe->writer;
$wh->autoflush(1);

print $wh  "thread# ",threads->tid()," -> $start, $finish, $pipe \n"  
+;

sleep 5;

print $wh  "thread# ",threads->tid()," -> finishing \n"  ;
sleep 2;

}

__END__

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Old Perl Programmer Haiku ................... flash japh

In reply to Re^7: how to split huge file reading into multiple threads by zentara
in thread how to split huge file reading into multiple threads by sagarika

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