Hi waytoperl

I would side with Discipulus here and surmise that your problem is in regard to simultaneously printing the output into multiple filehandles, or multiplexing.

For me it seemed clear that using the single form of perlfunc:select would be necessary to achieve simple multiplexing. However, I managed to rework the code around the perlfunc:pipe function. Thank Strawberry (and Perlmonks) for perldoc.

Essentially, once you have selected a filehandle, the filehandle_special-variables are operational on that filehandle

Any regular output run in a perlfunc:system call will go to that output filehandle, but there, as in the code here, any redirections within the external script, will behave as scripted.

The perlfunc:pipe perlfunc:fork combo sets up a situation where you may select the output filehandle to only print to the output, or select the pipe $writer indirect filehandle, to print to both (or as many as you like) at the same time.

Best not to redirect 0,1,2 unless you understand it well. Even though I have done so here, I am very confident there are better ways. Discipulus' link to log4Perl premise is definetly worth another look.

#!/usr/bin/perl -w

use strict;
use feature qw{ say };
use File::Spec::Functions qw{ catfile };
use Fcntl;
use IO::Handle;

# special Filehandle variables, 
# operate on currently selected fh
$|++;

open my $output, '>', catfile( qw( . output.txt ) )
   or die q{ output open fail },$!;

my $original_selected_default_output =  select $output; $|++;
select $original_selected_default_output;

my $reader = IO::Handle->new();
my $writer = IO::Handle->new();

(select($_),$|++) foreach ($reader,$writer,'STDOUT'); 

pipe($reader,$writer) or die "not today $!";

my $pid = fork();

 if( $pid == 0 ){

    close $writer; 
    open my $stdout, '>&', 'STDOUT'
       or die 'aaaarrrggh!',$!;  

    my @filehandles = ( $stdout, $output ); 

    say( 'firstly from reader' ) foreach($stdout,$output);

    while(my $l = <$reader>){ 
       foreach my $fh ( @filehandles ){
           say { $fh } 'from ',$l, ' reader';
        }
    }continue{} # this is distilled genius  

    say( 'finely from reader' ) foreach( $stdout, $output );
    
    select $original_selected_default_output ;
    close $reader;    
    exit 0;
 
  }elsif($pid){   
    close $reader; 
  }else{ 
    die "there is far better error handling to be had here $!"
  }

# say to ./output.txt
select $output;
say localtime(time),q{ All I need to say is use feature };

# say to both
select $writer;
say localtime(time),' using say is straightforward for simple output';

# set back to good ol' STDOUT
select $original_selected_default_output 
  or die "not working $!";

# clear up the pipe
close $writer;

#scrap most of todays code
#sleep 1; 
say localtime(time),q{ snoozing};

say 'quick, gotta go to bed';

exit 0;
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.