#!/usr/bin/perl
use strict;
use warnings;

use Tk;
use Tk::ROText;
use IO::File;
use POSIX qw/tmpnam/;
use File::Basename qw/dirname/;

use FindBin;

#
# create tempory file name:
#
my $File;
my $Handle;
my $Mw;
{
    do {
        $File = tmpnam();
    }
    until my $fh = new IO::File ($File, O_RDWR | O_CREAT | O_EXCL);
}
print "File: [$File]\n";



#
# create $File and open $Handle:
#
fill_in();
system('ls', '-l', dirname($File));
open($Handle, "tail -f $File|") or die "Nope: $!";

#
# Start Tk
#
tk_start();
exit;


sub tk_start {
    my $mw = $Mw = new MainWindow;
    #$mw->title("fileevent.pl - tmpfile: [$File]"); 

    $mw->Label(
        -text  => "tmpfile: [$File]",
        -anchor => 'w',
    )->pack(
        -fill   => 'x',
        -expand => 0,
    );

    $mw->Button(
        -text => 'Daten in Datei schreiben',
        -command => \&fill_in,
    )->pack(
        -fill   => 'x',
        -expand => 0,
        -padx   => 10,
        -pady   => 10,
        -ipadx  => 10,
    );

    my $t = $mw->Scrolled(
        'ROText',
        -scrollbars => 'oe',
        -height     => 10,
        -width      => 50,
    )->pack(
        -fill   => 'both',
        -expand => 1,
        -pady   => 10,
    );

    $mw->fileevent(\*$Handle, 'readable', [ \&fill_text_widget, $t ]);

    MainLoop();

} # sub tk_start

sub fill_in {
    system("date >> $File");
}

sub fill_text_widget {
    my ($widget) = @_;

    my $stat = sysread $Handle, $_, 4096;
    die "sysread error:  $!" unless defined $stat;

    $widget->insert('end', $_);
    $widget->yview('end');

} # sub fill_text_widget

END {
    print "Anfang vom ENDE\n";
    #$Mw->fileevent(\*$Handle, 'readable');
    #$Handle->close();
    unlink $File or die "Konnte '$File' nicht loeschen: $!";
    print "Ende vom ENDE\n";
    system "kill -9 $$";
} # END