#!/usr/bin/perl

use strict;
use warnings;
use Fcntl;
use POSIX ":sys_wait_h";
use IPC::Open3;
use IO::Handle;
use IO::Select;

my $out = shift @ARGV;
die unless @ARGV;

open my $fout, ">>", $out or die "Can't write to $out: $!" if $out;

my $select = IO::Select->new();
my $alive = 1;
my $pid;
my $interactive = -t STDOUT;

my $code;
sub sigchld
{
	my $kid;
	do {
		$kid = waitpid( -1, WNOHANG );
		if ( $kid == $pid ) {
			$code = $? >> 8;
			$alive = 0
		}
	} while ( $kid > 0 );
}
$SIG{CHLD} = \&sigchld;

$pid = open3( "<&STDIN",  \*child_out, \*child_err, @ARGV );

sub sethandle
{
	my $h = shift;
	my $flags = 0;

	fcntl ( $h, F_GETFL, $flags )
		or die "Couldn't get flags for HANDLE : $!\n";
	$flags |= O_NONBLOCK;
	fcntl ( $h, F_SETFL, $flags )
		or die "Couldn't set flags for HANDLE: $!\n";

	$select->add( $h );
}

sethandle( \*child_out );
sethandle( \*child_err );

while ( $alive ) {
	foreach my $h ( $select->can_read() ) {
		sysread $h, $_, 102400;
		print $fout $_ if $fout;
		if ( $interactive && $h == \*child_err ) {
			print "\033[31m$_\033[0m";
		} else {
			print $_;
		}
		STDOUT->flush();
	}
}

exit $code;