#!/usr/bin/perl
use English;

## name of log file is passed by the backup script, get PID of backup (parent) script
$ppid = getppid;

## print "\$ppid: $ppid\n\n";
$logfile = @ARGV[0];
$lastlc  = @ARGV[1];

## print "\$lastlc: $lastlc\n\n";
## look to see if backup job is still running
## run while backup job is still running
while (getppid == $ppid) {
   ## how many lines are currently in the $logfile?
   $wc = `wc $logfile`;
   @awc = split " ", $wc;
   $linect = $awc[0];
   ## are there are more lines than the last time we checked?
   if ($linect > $lastlc) {
      ## display the new lines in the log file.
      &ShowLog ($linect, $lastlc);
      $lastlc = $linect;
   }
   ## I want to sleep for 5 seconds, you can make this shorter if you like.
   ## I don't recommend not sleeping though, since it will chew up CPU cycles
   sleep 5;
}

## backup job is no longer running
## check to see if any new lines have been added
$wc = `wc $logfile`;
@awc = split " ", $wc;
$linect = $awc[0];
if ($linect > $lastlc) {
   ## display new log file lines
   &ShowLog ($linect, $lastlc);
   $lastlc = $linect;
}

exit;

sub ShowLog {
   my ($linect, $lastlc) = @ARG;
   ## determine how many lines have been added
   $showlines = $linect - $lastlc;
   ## use tail command to display newly appended lines
   ## print "$showlines = $linect - $lastlc\n\n";
   system "tail -$showlines $logfile";
}