Hi,

> ruby-1.9.2-p136 :009 > data = StringIO.new( open( 'test.zip', 'r' ).read )

I see that you want to read a ZIP format file, "test.zip". Right?

> ruby-1.9.2-p136 :010 > Zlib::GzipReader.new(data).read
> Zlib::GzipFile::Error: not in gzip format

However, you used Zlib::GzipReader. This class is used for not zip format,
but gzip format [1], so that error occurred.

One way to unzip a file is to use zipruby gem [2]. Please try it.

[1] http://www.ruby-doc.org/stdlib/libdoc/zlib/rdoc/classes/Zlib/GzipReader.html
[2] https://rubygems.org/search?utf8=%E2%9C%93&query=zipruby

Regards,
-- 
NOBUOKA Yu
http://www.vividcode.info/