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我正在用Ruby編寫一個程序，將RSS源中的文件下載到我的本地硬盤。以前，我用Perl編寫了這個應用程序，並認爲一種學習Ruby的好方法就是使用Ruby代碼重新創建該程序。直接從RSS源下載文件使用Ruby - 處理重定向
在Perl程序（它的工作原理）中，我能夠直接從它所在的服務器上下載原始文件（保留原始文件名）並且工作得很好。在Ruby程序中（這不起作用），我必須將我想要的文件中的數據「流」到我在硬盤上創建的新文件中。不幸的是，這不起作用，「流」數據總是回到空白。我的假設是，Perl可以處理某種類型的重定向來直接檢索文件，而Ruby不能。
我打算髮布這兩個程序（它們相對較小），並希望這有助於解決我的問題。如果您有問題，請告訴我。作爲一個便箋，我指出這個程序在一個更加靜態的URL（一個jpeg）上，並且它下載了這個文件就好了。這就是爲什麼我推理某種重定向導致了問題。
Ruby代碼（不工作）
require 'net/http';
require 'open-uri';
require 'rexml/document';
require 'sqlite3';
# Create new SQLite3 database connection
db_connection = SQLite3::Database.new('fiend.db');
# Make sure I can reference records in the query result by column name instead of index number
db_connection.results_as_hash = true;
# Grab all TV shows from the shows table
query = '
SELECT
id,
name,
current_season,
last_episode
FROM
shows
ORDER BY
name
';
# Run through each record in the result set
db_connection.execute(query) { |show|
# Pad the current season number with a zero for later user in a search query
season = '%02d' % show['current_season'].to_s;
# Calculate the next episode number and pad with a zero
next_episode = '%02d' % (Integer(show['last_episode']) + 1).to_s;
# Store the name of the show
name = show['name'];
# Generate the URL of the RSS feed that will hold the list of torrents
feed_url = URI.encode("http://btjunkie.org/rss.xml?query=#{name} S#{season}E#{next_episode}&o=52");
# Generate a simple string the denotes the show, season and episode number being retrieved
episode_id = "#{name} S#{season}E#{next_episode}";
puts "Loading feed for #{name}..";
# Store the response from the download of the feed
feed_download_response = Net::HTTP.get_response(URI.parse(feed_url));
# Store the contents of the response (in this case, XML data)
xml_data = feed_download_response.body;
puts "Feed Loaded. Parsing items.."
# Create a new REXML Document and pass in the XML from the Net::HTTP response
doc = REXML::Document.new(xml_data);
# Loop through each in the feed
doc.root.each_element('//item') { |item|
# Find and store the URL of the torrent we wish to download
torrent_url = item.elements['link'].text + '/download.torrent';
puts "Downloading #{episode_id} from #{torrent_url}";
## This is where crap stops working
# Open Connection to the host
Net::HTTP.start(URI.parse(torrent_url).host, 80) { |http|
# Create a torrent file to dump the data into
File.open("#{episode_id}.torrent", 'wb') { |torrent_file|
# Try to grab the torrent data
data = http.get(torrent_url[19..torrent_url.size], "User-Agent" => "Mozilla/4.0").body;
# Write the data to the torrent file (the data is always coming back blank)
torrent_file.write(data);
# Close the torrent file
torrent_file.close();
}
}
break;
}
}
Perl代碼（即不工作）
use strict;
use XML::Parser;
use LWP::UserAgent;
use HTTP::Status;
use DBI;
my $dbh = DBI->connect("dbi:SQLite:dbname=fiend.db", "", "", { RaiseError => 1, AutoCommit => 1 });
my $userAgent = new LWP::UserAgent; # Create new user agent
$userAgent->agent("Mozilla/4.0"); # Spoof our user agent as Mozilla
$userAgent->timeout(20); # Set timeout limit for request
my $currentTag = ""; # Stores what tag is currently being parsed
my $torrentUrl = ""; # Stores the data found in any node
my $isDownloaded = 0; # 1 or zero that states whether or not we've downloaded a particular episode
my $shows = $dbh->selectall_arrayref("SELECT id, name, current_season, last_episode FROM shows ORDER BY name");
my $id = 0;
my $name = "";
my $season = 0;
my $last_episode = 0;
foreach my $show (@$shows) {
$isDownloaded = 0;
($id, $name, $season, $last_episode) = (@$show);
$season = sprintf("%02d", $season); # Append a zero to the season (e.g. 6 becomes 06)
$last_episode = sprintf("%02d", ($last_episode + 1)); # Append a zero to the last episode (e.g. 6 becomes 06) and increment it by one
print("Checking $name S" . $season . "E" . "$last_episode \n");
my $request = new HTTP::Request(GET => "http://btjunkie.org/rss.xml?query=$name S" . $season . "E" . $last_episode . "&o=52"); # Retrieve the torrent feed
my $rssFeed = $userAgent->request($request); # Store the feed in a variable for later access
if($rssFeed->is_success) { # We retrieved the feed
my $parser = new XML::Parser(); # Make a new instance of XML::Parser
$parser->setHandlers # Set the functions that will be called when the parser encounters different kinds of data within the XML file.
(
Start => \&startHandler, # Handles start tags (e.g.)
End => \&endHandler, # Handles end tags (e.g.
Char => \&DataHandler # Handles data inside of start and end tags
);
$parser->parsestring($rssFeed->content); # Parse the feed
}
}
#
# Called every time XML::Parser encounters a start tag
# @param: $parseInstance {object} | Instance of the XML::Parser. Passed automatically when feed is parsed.
# @param: $element {string} | The name of the XML element being parsed (e.g. "title"). Passed automatically when feed is parsed.
# @attributes {array} | An array of all of the attributes of $element
# @returns: void
#
sub startHandler {
my($parseInstance, $element, %attributes) = @_;
$currentTag = $element;
}
#
# Called every time XML::Parser encounters anything that is not a start or end tag (i.e, all the data in between tags)
# @param: $parseInstance {object} | Instance of the XML::Parser. Passed automatically when feed is parsed.
# @param: $element {string} | The name of the XML element being parsed (e.g. "title"). Passed automatically when feed is parsed.
# @attributes {array} | An array of all of the attributes of $element
# @returns: void
#
sub DataHandler {
my($parseInstance, $element, %attributes) = @_;
if($currentTag eq "link" && $element ne "\n") {
$torrentUrl = $element;
}
}
#
# Called every time XML::Parser encounters an end tag
# @param: $parseInstance {object} | Instance of the XML::Parser. Passed automatically when feed is parsed.
# @param: $element {string} | The name of the XML element being parsed (e.g. "title"). Passed automatically when feed is parsed.
# @attributes {array} | An array of all of the attributes of $element
# @returns: void
#
sub endHandler {
my($parseInstance, $element, %attributes) = @_;
if($element eq "item" && $isDownloaded == 0) { # We just finished parsing an element so let's attempt to download a torrent
print("DOWNLOADING: $torrentUrl" . "/download.torrent \n");
system("echo.|lwp-download " . $torrentUrl . "/download.torrent"); # We echo the "return " key into the command to force it to skip any file-overwite prompts
if(unlink("download.torrent.html")) { # We tried to download a 'locked' torrent
$isDownloaded = 0; # Forces program to download next torrent on list from current show
}
else {
$isDownloaded = 1;
$dbh->do("UPDATE shows SET last_episode = '$last_episode' WHERE id = '$id'"); # Update DB with new show information
}
}
}