in reply to Diagnosing blocking io (or: finding the WHY of my Open2 woes).

Just for the sake of experimenting, you could try a sysread instead of the <> operator, and grab 1 byte at a time. 
  while (my $nread = sysread($JSREAD, my $buf, 1)) {
        print  $buf; 
       last if $nread == 0;
        }

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Re^2: Diagnosing blocking io (or: finding the WHY of my Open2 woes).
by Socrates (Acolyte) on Nov 19, 2008 at 18:21 UTC
    I commented out the line 
    my @output=<$JSREAD>;

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    And replaced it with that code, but but there was no observable difference.
[reply]
[d/l]
      Well, at least now you know that ikegami was right, it's not a Perl piping problem, your js program isn't outputting correctly. Here is a pty example you might want to try. 
      #!/usr/bin/perl -w
# Description: Fool a process into
# thinking that STDOUT is a terminal, when in fact
# it may be a file or a pipe. This can be useful
# with programs like ps and w on linux... which
# will trunc their output to the width of the
# terminal, and, if they cannot detect the terminal
# width, use a default 80 columns. Wouldn't it be
# nice to say "ps -aux | grep etcshadow", and get
# output that looks like when you just say "ps
# -aux"? Well, that's the idea.

#try ./pseudotty "xterm -e top"
#or  ./pseudotty top

use warnings;
use strict; 
use IO::Pty; 

die "usage: ptyexec command [args]\n" unless @ARGV;

my $pty = IO::Pty->new; 
my $slave = $pty->slave;
open TTY,"/dev/tty" or die "not connected to a terminal\n"; 
$pty->clone_winsize_from(\*TTY);
close TTY;

my $pid = fork(); die "bad fork: $!\n" unless defined $pid; 
if (!$pid) {
#  $slave->close();
  open STDOUT,">&=".$pty->fileno() or die $!;
  exec @ARGV;
}else{
  $pty->close();
     while (defined (my $line = <$slave>)) {
       print $line;
     }
}

#cleanup pty for next run
$pty->close();

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      I'm not really a human, but I play one on earth Remember How Lucky You Are
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[d/l]

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