#!/usr/bin/perl
#
# $Id: lockit.pl,v 1.3 2003/01/13 05:28:42 jmates Exp $
# Jeremy Mates <mailto:jmates@sial.org>
#
# Attempts to lock files.
# 
# For documentation, use the -h option or run perldoc on this script.
#
# Distributed under the Artistic License:
# http://sial.org/artistic_license.txt
#
######################################################################
#
# MODULES

use Carp;
use Getopt::Std;

# file locking related modules
use Fcntl qw(:DEFAULT :flock);
use IO::Handle;

use strict;
use vars qw:$VERSION:;

######################################################################
#
# CONSTANTS

my (%opts);

($VERSION = '$Revision: 1.3 $ ') =~ s/[^0-9.]//g;

######################################################################
#
# MAIN

# parse command-line options
getopts('h?z', \%opts);

help() if exists($opts{'h'}) || exists($opts{'?'});

my $logfile = shift; # filename to lock

# attempt lock on named file...
# open & aquire write lock on the logfile
open (FD, "+< $logfile") or die "Error opening $logfile: $!\n";
FD->autoflush(1);
    
unless (flock (FD, LOCK_EX|LOCK_NB)) {
    warn "Waiting for write lock on $logfile ...\n";
    flock (FD, LOCK_EX);
}

# zap the file if you want to...
if (exists $opts{'z'}) {
    seek     (FD, 0, 0) or die "Problem seeking $logfile: $!\n";
    truncate (FD, 0) or die "Problem truncating $logfile: $!\n";
}

sleep 60;

flock (FD, LOCK_UN);
close (FD);

######################################################################
#
# SUBROUTINES

# a generic help blarb
sub help {
    print <<"HELP";
$0 v.$VERSION
Usage: $0 [options] [LOGFILE]
Purpose: simple file locker.

Options:
  -h/-?  Display this message

  -z     Zap the file (empty contents thereof), too.

Run perldoc on this script for more documentation.

HELP
    exit;
}

__END__

=head1 NAME

lockit.pl - simple file locker.

=head1 SYNOPSIS

Pretty simple, just run:

  $ lockit.pl

=head1 DESCRIPTION

Locks files, or gives it a good shot, anyways.

Sleeps for 60 seconds, probably enough for you to test stuff.

=head1 USAGE

  $ lockit.pl [options] LOCKFILE

=head1 OPTIONS

lockit.pl supports the following command line options:

-h     Get a brief help blarb

-z     Zap the file.

Truncates the file down the 0 bytes.

=head1 LICENSE

This script is distributed under the terms of the Artistic License:

http://sial.org/artistic_license.txt

=head1 BUGS

Lots, probably.

=head1 SEE ALSO

flock(2), perl(1)

=head1 AUTHOR

Jeremy Mates, jmates@sial.org

=cut