#!/usr/bin/perl -w
#
# pipe-watcher
# John Simpson 2005-10-07
#
# watch a pipe for activity
# when it sees activity, runs a script
#
###############################################################################
#
# Copyright (C) 2005 John Simpson.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 2, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
# or visit http://www.gnu.org/licenses/gpl.txt
#
###############################################################################

require 5.003 ;
use strict ;

$| = 1 ;

# the name of the pipe to watch
my $pfile		= "/tmp/update-qmail" ;

# the script (or program) we run whenever activity is seen
my $cmd			= "/service/qmail-updater/update-qmail" ;
my $cmd_needs_data	= 0 ;

# delay (in seconds) to keep the program from being flooded
my $min_delay		= 5 ;

###############################################################################
###############################################################################
###############################################################################

print "starting\n" ;

unlink $pfile ;
system "mkfifo -m u=rw,go=w $pfile" ;

unless ( -p $pfile )
{
	print "ERROR: Can\'t create fifo $pfile: $!\n" ;
	sleep 30 ;
	exit 1 ;
}

my @s = stat $pfile ;
unless ( $< == $s[4] )
{
	print "ERROR: My uid doesn't own $pfile (me=$< owner=$s[4])\n" ;
	sleep 30 ;
	exit 1 ;
}

my $lastrun = 0 ;

while ( 1 )
{
	my $text = "" ;
	my ( $rv ) ;

	### wait on the pipe to give us data

	print "waiting for input on $pfile\n" ;
	open ( I , "<$pfile" ) or die "Can\'t open $pfile for reading: $!\n" ;

	print "gathering input\n" ;
	while ( my $line = <I> )
	{
		$text .= $line ;
	}
	close I ;

	chomp $text ;
	print "/-----\n$text\n\\-----\n" ;

	$lastrun = time ;

	########################################
	# run the command.
	# the input from the pipe is in "$text" if you need it.
	# remember to include "2>&1" in your command if you want
	#   the output from the command to end up in the log file

	print "running [$cmd] (output follows)\n/-----\n" ;

	if ( $cmd_needs_data )
	{
		if ( open ( C , "| $cmd 2>&1" ) )
		{
			print C $text ;
			close C ;
			print "\\-----\n" ;
		}
		else
		{
			print "\\----- Unable to run: $!\n" ;
		}
	}
	else
	{
		$rv = system ( "$cmd 2>&1" ) ;
		print "\\----- rv=$rv\n" ;
	}

	if ( time < ( $lastrun + $min_delay ) )
	{
		my $nsec = $lastrun + $min_delay - time ;
		print "sleeping $nsec seconds...\n" ;
		sleep $nsec ;
	}
}