wget-monitor

#!/usr/bin/perl
#
# wget-monitor -- simple URL monitor
#
# Stick a list of URLs in ~/.wget-monitor, one per line, (blank lines
# and comment lines with '#' allowed) for wget to retrieve.  First
# invocation fetches the URLs into a local cache; subsequent
# invocations diff the online version against the cache.
#
# Copyright (c) 2003 Adam Spiers <adam@spiers.net>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# 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, see <http://www.gnu.org/licenses/>.

use strict;
use warnings;

use File::Basename;
use File::Path;
use File::Temp 'tempdir';

open(CFG, "$ENV{HOME}/.wget-monitor")
  or die "$0: $!\n";

my $cache = "$ENV{HOME}/.wget-monitor-cache";
-d $cache or mkdir $cache;

my $tempdir = tempdir("/tmp/wget-monitor-XXXXXXX", CLEANUP => 1);

my $changes = 0;
while (<CFG>) {
  next if /^\s*#/ || /^\s*$/;

  chomp;

  m!^((http|ftp):)//! or die "Weird line $.:\n$_\n";
  my $proto = $1;

  chdir $tempdir or die "chdir($tempdir) failed: $!\n";
  my $wget = `wget -nv -x "$_" 2>&1`;
  my ($path) = $wget =~ /-> "(.+)"/
    or die "Weird output from wget:\n$wget\n";
  my $new = "$tempdir/$path";
  my $old = "$cache/$proto/$path";

  if (-e $old) {
    my $diff = `diff -u "$old" "$new"`;
    if ($diff) {
      $changes++;
      $diff =~ s!^--- $cache/!--- !m;
      print $diff;
    }
  }
  else {
    my $dir = dirname($old);
    mkpath($dir, 0, 0700) or die "mkpath($dir) failed: $!\n";
  }

  rename $new, $old
    or warn "rename($new, $old) failed: $!\n";
}

exit $changes;