Often I find myself doing tail -f file | grep --line-buffered "kernel" and your program has given me the inspiration to automate that. This is my version. It features taint mode and File::Tail:

#!/usr/bin/perl -T

use strict;
use warnings;
use File::Tail;

die "Not enough arguments\n" unless @ARGV;
my ($file, $regex) = @ARGV;
$regex = '.' unless defined $regex && length $regex;

my $tail = File::Tail->new (
    name        => $file,
    maxinterval => 5,
    adjustafter => 10,
);

$SIG{ALRM} = sub { printf "\n%s\n", '='x80; };

while (defined ($_ = $tail->read)) {
    print && alarm 2 if /$regex/;
}

[download]

Let me anticipate that someone is going to reply talking about code interpolation in the regex:

# ~/bin/tf2.pl file '(??{print "Hello, world!\n"})'
Eval-group not allowed at runtime, use re 'eval' in regex m/(??{print 
+"Hello, world!\n"})/ at /root/bin/tf2.pl line 20.

[download]

Update: Minor change according to imp's comment.

--
David Serrano

In reply to Re: tf - tail a file and output separator line when inactive by Hue-Bond
in thread tf - tail a file and output separator line when inactive by imp

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