Seems to work just fine but it doesn't make me happy. Perhaps this might offer a clue to someone else who does know what's going on?

-mark

Hm. Weird. I've modified code like this:

#!/usr/bin/perl -w

use Time::HiRes;

$SIG{"ALRM"}=\&sigAlarm;

my $interval=1;
my $uInterval=$interval*10**6;
Time::HiRes::ualarm($uInterval, $uInterval);
open TAIL, "tail -f xyz|" or die 'couldnt open xyz';
while (1)
{
  while ($line=<TAIL>)
  {
      $X = $!;
      print $line;
  }
  if (eof(TAIL)) {
    print "EOF TAIL!\n";
  }
  print "Fell through... $!\n";
}

sub sigAlarm
{
    print "alarm\n";
}
[download]

After first EOF found, it never works normal again. It just prints EOF TAIL + Fell through... in infinite loop. So, I think filehandle never recovered after Perl finds EOF.

I think the problem is once you've done the first $line=<TAIL> it's too late. Here's what I wrote that DOES work correctly and will not exit the loop, but as I said I'm not proud of it ;):

#!/usr/bin/perl -w

use Time::HiRes;

$SIG{"ALRM"}=\&sigAlarm;

my $interval=1;
my $uInterval=$interval*10**6;
Time::HiRes::ualarm($uInterval, $uInterval);

my $logname='xyz';
open TAIL, "tail -f $logname|" or die "couldn't open $logname";
while (1)
{
  while(1)
  {
    if (eof(TAIL))
    {
      printf "EOF: %d\n", eof(TAIL);
      $line=<TAIL>;
      next;
    }

    last    if !($line=<TAIL>);
    print $line;
  }
  print "Fell through...\n";
}

sub sigAlarm
{
  print "alarm\n";
}
[download]

I also wonder if doing that eof() test at the beginning go throw me into an infinite loop under some conditions, but as so far this seems to be ok for now.

-mark