Syntax error by using ruby-youtube-dl - ruby

Question

i'm new to this site and also in programming. Actually i'm learning Ruby.
In my first experiments i would like to download a file from Youtube. I decided to use ruby-youtube-dl.
I parse ARGV0 to $url.
Then i'm using:
FileUtils.cd("#{$musicdir}/#{$folder}") do
YoutubeDL::Downloader.download_audio("#{$url}")
end
But that one produces that output:
sh: -c: Zeile 0: Syntaxfehler beim unerwarteten Wort `('
sh: -c: Zeile 0: `/home/sascha/.rvm/gems/ruby-2.0.0-p353/gems/ruby-youtube-dl-0.0.5/bin/youtube-dl.py --no-progress --extract-audio --audio-format=mp3 --output=/tmp/%(stitle)s-%(uploader)s-%(autonumber)s.mp3'
/home/sascha/.rvm/gems/ruby-2.0.0-p353/gems/ruby-youtube-dl-0.0.5/lib/ruby-youtube-dl/downloader.rb:9:in `download_audio': undefined method `[]' for nil:NilClass (NoMethodError)
from /home/sascha/RubymineProjects/ruby_script_collection/youtube_dlhelper/lib/youtube_dlhelper.rb:86:in `block in <top (required)>'
from /home/sascha/.rvm/rubies/ruby-2.0.0-p353/lib64/ruby/2.0.0/fileutils.rb:125:in `chdir'
from /home/sascha/.rvm/rubies/ruby-2.0.0-p353/lib64/ruby/2.0.0/fileutils.rb:125:in `cd'
from /home/sascha/RubymineProjects/ruby_script_collection/youtube_dlhelper/lib/youtube_dlhelper.rb:84:in `<top (required)>'
from -e:1:in `load'
from -e:1:in `<main>'
The full sourcefile is placed there: http://pastebin.com/jAwjHanw
Maybe anyone can help out?

Answer 1

I've looked into the log, and it seems to be a bug. You can do the following steps the solve, or partially solve the problem:
Check out gem:
$ cd ~/git
$ git clone https://github.com/bnmrrs/ruby-youtube-dl.git
Specify the path folder in your project's Gemfile that will point to the newly checked out gem:
gem 'ruby-youtube-dl', :path => '~/git/ruby-youtube-dl'
Try to fix the gem locally, for example by removing parentheses, and # chars, and replacing them with constants. Of course it will be a workaround.
In case if you are developing a gem or rails app, you shell to publish you changes to web, and you are able to do that by forking the gem on github, pushing you changed into you version branch:
$ git clone git://github.com/yourname/ruby-youtube-dl.git
$ cd ruby-youtube-dl
$ git branch fixbranch
$ git checkout fixbranch
# do your changes...
$ git push origin fixbranch
Use your changes as the main gem version. In this case you are need to change your Gemfile for example as follows:
gem 'ruby-youtube-dl', :git => 'git://github.com/yourname/ruby-youtube-dl.git', :branch => 'fixbranch'
In case if your changes are not workaround you can open a pull request on github to commit your changes into the mainstream.
If you are unable to solve the problem even with a workaround, it will be beast to report the issue to the gem developers here, supplying the error logs unto them.