How do I tail -f a file if it is NFS mounted?

[tim]

The standard answers to this question, found in the FAQ and in the perl cookbook, don't seem to be working. I'd like to avoid a tell-close-open-seek series of calls, as it seems that would add a lot of overhead.

Originally posted as a Categorized Question.

[lhoward]

I've used this technique before with quite a bit of success. Only problem is that it can't detect a "real" EOF (writer has stopped writing to the file) but that will be the case with just about any method:

#!/usr/bin/perl -w
use IO::File;
use strict;

my $tail = new IO::File;
$tail->open("<./log.dat");

while(1){
  my @lines=$tail->getlines();
  if(0==scalar(@lines)){
    # wait 1 second before trying again...
    # to keep from hogging CPU cycles
    sleep 1;
  }else{
    my $line;
    foreach $line(@lines){
      chomp $line;
      print "  \"$line\"\n";
    }
  }
}

[merlyn]

I would use File::Tail.

[tim]

Whoops :( My implementation of the example found in "perldoc -f seek" was incomplete. This one seems to work:

    for (;;) {
        for ($curpos = tell(FILE); $_ = <FILE>;
             $curpos = tell(FILE)) {
            # search for some stuff and put it into files
        }
        sleep($for_a_while);
        seek(FILE, $curpos, 0);
    }

I'm really not that much of an idiot. really.