rsiedl has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,

I am attempting to write a script which will check back with the main server for the latest version.

Currently I am using LWP::Simple to fetch a copy of the script from the main server and would like to pull $VERSION out of that.

I have several questions:

1. Can anyone see a problem with this method or suggest a better one?
2. Is there a way to temporarily evaluate the code I pull in so I can get the version via something like $temp::VERSION?

Any help would be appreciated. I've attached my test code below

Cheers,
Reagen

#!/usr/bin/perl

use strict;
use warnings;
use LWP::Simple;

BEGIN {
  use vars qw($VERSION $PID);
  $VERSION = '0.01';
  $PID = "/var/run/test.pid";

  # create our running pid file
  open PID, "> $PID";
  print PID $$;
  close PID;

  # check we are the latest version
  my $content = get("http://www.someurl.com/software/$0");
  die "Couldn't get it!" unless defined $content;

  # can we eval $content to get $VERSION?
  $SERVER_VERSION = 0;
  print "Server version: $SERVER_VERSION\n";
  print "Local version: $VERSION\n";

} # end-begin

# cleaning up
END {
  `rm -f /$PID`;
} # end-end

exit;

[download]

Replies are listed 'Best First'.
Re: Checking for latest version
by Anonymous Monk on Jan 06, 2010 at 03:20 UTC
    Why would you be using eval? See Perl::Version

    http://code.google.com/p/get-flash-videos/ 

    sub update {
  if($::SCRIPT_NAME) {
    my $browser = FlashVideo::Mechanize->new;

    $browser->get("http://get-flash-videos.googlecode.com/svn/wiki/Ver
+sion.wiki");

    if(!$browser->response->is_success) {
      die "Unable to retrieve version data: " . $browser->response->st
+atus_line;
    }

    my $version = ($browser->content =~ /version: (\S+)/)[0];
    my $base = ($browser->content =~ /from: (\S+)/)[0];
    my $info = ($browser->content =~ /info: (\S+)/)[0];
    my $url = $base . $::SCRIPT_NAME . "-" . $version;

    die "Unable to parse version data" unless $version and $base;

    my @v = split /\./, $version;
    my @V = split /\./, VERSION;

    my $newer = 0;
    my $i = 0;
    for(@v) {
      $newer = 1 if !defined $V[$i] || $_ > $V[$i];
      last if $V[$i] > $v[$i];
      $i++;
    }

    if($newer) {
      info "Newer version ($version) available, downloading..";
      die "Cannot update -- unable to write to $0\n" unless -w $0;

      my $new_file = $0 . ".new";
      $browser->mirror($url, $new_file);

      if($browser->response->is_success && -f $new_file) {
        rename $0, "$0.old" or die "Unable to rename $0 to $0.old: $!"
+;
        rename $new_file, $0 or die "Unable to rename $new_file to $0:
+ $!";
        chmod 0755, $0;

        info "New version installed as $0";
        info "(previous version backed up to $0.old).";
        info $info;
        exit 0;
      } else {
        die "Download failed: " . $browser->response->status_line;
      }
    } else {
      print STDERR "You already have the latest version.\n";
    }
  } else {
    info "Development version, not updated";
  }

  update_plugins();
}

    [download]
    Also see PAR::WebStart
[reply]
[d/l]
Re: Checking for latest version
by mykl (Monk) on Jan 06, 2010 at 10:26 UTC

    Would you consider comparing by the datestamp on the file rather than the version number? Then you could just use the mirror() method of LWP::Simple to check that the script is up to date, and download the newer version if not. However, whether a datestamp comparison is safe will depend on your particular application - whether an older version could ever get a newer datestamp.

    --

    "Any sufficiently analyzed magic is indistinguishable from science" - Agatha Heterodyne

[reply]
[d/l]

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