Fix: 

#!/usr/bin/perl

use strict;
use warnings;

use IO::Select ();
use IPC::Open3 qw( open3 );

$|++;

my $BLOCK_SIZE = 1024;

my $script = shift;
my $pid = open3(undef, \*OUT, \*ERR, "./$script @ARGV");

my $r_sel = IO::Select->new(\*OUT, \*ERR);

my $out = '';
my $err = '';

MAIN_LOOP:
for (;;) {
   my @r = $r_sel->can_read();

   foreach (@r) {
      last MAIN_LOOP if eof($_);
      my $dp = ($_ == \*OUT ? \$out : \$err);
      1 while read($_, $$dp, $BLOCK_SIZE, length($$dp));
   }
}

waitpid($pid, 0);  # Reap child.

print("STDOUT: $out\n");
print("STDERR: $err\n");

[download]

Tested.

It gets more complex if you have multiple children, or if you do bidirectional communication. Refer to Using 'select' to handle multiple sockets to do those things.

I think you can use -s $_ instead of $BLOCK_SIZE on linux (thus eliminating the need for the while loop), but it doesn't work on other OSes such as FreeBSD.

In reply to Re: Script hangs when called via IPC::Open3 (Solution) by ikegami
in thread Script hangs when called via IPC::Open3 by jeffa

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