#!/usr/bin/perl
# Time-stamp: "2005-08-19 01:37:15 ADT"     sburke@cpan.org
#desc{    diffs the active crontab against a given file    }

use strict;
my $x;
unless(@ARGV == 1 and defined($x = $ARGV[0]) and length $x
  and -e $x and -f _
) {
  require File::Basename;
  die "Usage: ", File::Basename::basename($0), " filespec\n";
}

my(@content) = (`crontab -l 2>&1`);   # Get the current crontab
print("[No crontab?]\n"), exit() unless @content;
print("[No crontab.]\n"), exit()
 if @content == 1 and $content[0] =~ m<^no crontab>si;

splice @content, 0, 3  # remove the hoohah that might be there.
   if @content >= 3
  and $content[0] =~ m<^# DO NOT EDIT THIS FILE>s
  and $content[1] =~ m<^# \(.* installed on>s
  and $content[2] =~ m<^# \(Cron version>s
;

# Make the temp file:
my $temp = "/tmp/diff_crontab_$$";
open(OUT, ">$temp") or die "Can't write-open $temp: $!";
print OUT @content;
close(OUT);

sleep 0;
my(@diffy) = `diff $temp $x`;

# So output goes:
#   < line in existing crontab, missing in new crontab
#   > line in new crontab, missing in existing crontab

sleep 0;
unlink $temp;  # nix temp file
print @diffy;
print "(No differences)\n" unless @diffy;
exit;