=head1 NAME

Tk::IO - high level interface to Tk's 'fileevent' mechanism

=for pm IO/IO.pm

=for category Binding Events and Callbacks

=head1 SYNOPSIS

  my $fh = Tk::IO->new(-linecommand => callback, -childcommand => callback);
  $fh->exec("command")
  $fh->wait
  $fh->kill

=head1 WARNING

INTERFACES TO THIS MODULE MAY CHANGE AS PERL'S IO EVOLVES
AND WITH PORT OF TK4.1

=head1 DESCRIPTION

Tk::IO is now layered on perl's IO::Handle class. Interfaces
have changed, and are still evolving.

In theory C methods which enable non-blocking IO as in earlier Tk-b*
release(s) are still there. I have not changed them to use perl's
additional Configure information, or tested them much.

Assumption is that B<exec> is
used to fork a child process and a callback is called each time a
complete line arrives up the implied pipe.

"line" should probably be defined in terms of perl's input record
separator but is not yet.

The -childcommand callback is called when end-of-file occurs.

$fh->B<wait> can be used to wait for child process while processing
other Tk events.

$fh->B<kill> can be used to send signal to child process.

=head1 BUGS

Still not finished.
Idea is to use "exec" to emulate "system" in a non-blocking manner.

=cut