Hello, Monks.
My first query here. I'm excited.

We have a number of machines (Slackware Linux, Perl 5.10) acting as data collectors: each has some number of serial inputs, each serial port writes to a file as stuff (ASCII text) arrives. There is a requirement for real-time viewing of incoming data -- the serial port data files. We came up with an application using Perl/Tk, but in the interest of minimizing our time rebuilding OS's we would rather stay away from X windows and instead have a simple curses application which would ordinarily be the only thing the data viewer user would see. The problem: using Curses::UI::TextViewer, no data ever displays.

To read the data file we discovered a number of sources which all recommended this method:

$errcode = open(FH, " tail -f $filename | ");
[download]

What none of these sources mentioned is that each time one of these filehandles is closed, an orphaned tail PID is left hanging out there. We came up with a little package for opening and closing the files which also tracks the tail PID's and disposes of them appropriately. The Perl/Tk code looks like this:

#!/usr/bin/perl
use strict;
use warnings;
use Tk;
require "./SFDTail.pm";
.
.
#  SFDTail.pm is our file handling package
my $tailer = SFDTail::new();
my $mw = MainWindow->new();
my $txtarea = $mw->Scrolled('Text', ... option stuff ...);
.
.
MainLoop;
.
.
#  grabtext() is our Tk::fileevent callback function
#  $tailer->fh() returns a file handle ($fh), created as:
#     open($fh, "tail -f -n 20 $self->{file} |");
sub grabtext
{
#  $stuff = <$tailer->fh()> don't work --??
 my $glob = $tailer->fh();
 my $stuff = <$glob>;
 $txtarea->insert('end', $stuff);
 $txtarea->yview('end');
}
.
.
#  Tk::Button event callback: select appropriate file, let $tailer ope
+n it.
#  $tailer->tail($file) is where the file gets opened, as above.
sub standard
{
 my $unit = shift;    # typically 'Unit01', 'Unit02', etc

#  clean up: close any previous filehandle and kill any tail PID's
 $tailer->closepipe();

 my $file = "/usr/local/scripts/tk/${unit}.txt";
 $txtarea->delete('1.0', 'end');

# if data input not active, the file may not be there
 if ( -f $file )
 {
  if ( $tailer->tail($file) )
  {
   $mw->fileevent($tailer->fh(), 'readable' => \&grabtext);
  }
 }
 else
 {
  $txtarea->insert('end', "\n No data for $unit. \n");
 }
}
[download]

The Perl/Tk thing works great, but trying to duplicate that in Curses:UI is not going so well. We're guessing that it's a blocking thing which somewhere between Tk::fileevent and Tk::Mainloop just gets quietly handled for us. We so far have been unable to get Curses::UI to go about its business and also display the results of the piped-tail filehandle. We would be most grateful for any suggestions, and thanks in advance.

< five days later >
Tried the select loop, but I guess I'm too dense to figure out how to get it to behave the way I needed it to. Finally found a workable solution using Curses::UI::POE and POE::Wheel::FollowTail. Thanks everybody for your consideration.