tailrate -- read STDIN, showing how many lines per X seconds; good for tailing an Apache access log, etc.

tailrate.pl

#!/usr/bin/perl

use strict;
use warnings;

# tailrate -- read STDIN, showing how many lines per X seconds
# Example invocation to tail a log file and print lines per second every 5 seconds:
#   tail -f /var/log/httpd/access_log | perl tailrate.pl 5

my $interval = shift || 1;
my $count = 0;
my $previous_count = 0;

alarm $interval;

$SIG{ALRM} = sub {
  alarm $interval;
  my $lines_per_sec = ($count - $previous_count) / $interval;
  print "$lines_per_sec lines per sec\n";
  $previous_count = $count;
};

while (<>) {
  $count++;
}