Recipe 12.11. Reading and Writing ZIP Files
Problem
You want to create or examine a ZIP archive from within Ruby code.
Solution
Use the
rubyzip gem. Its Zip module gives you several ways of putting files into ZIP archives, and taking them out again. The simplest interface is the Zip::ZipFileSystem, which duplicates most of the File and Dir operations within the context of a ZIP file. You can use this to create ZIP files:
require 'rubygems'
require 'zip/zipfilesystem'
Zip::ZipFile.open('zipfile.zip', Zip::ZipFile::CREATE) do |zip|
zip.file.open('file1', 'w') { |f1| f1 << 'This is file 1.' }
zip.dir.mkdir('subdirectory')
zip.file.open('subdirectory/file2', 'w') { |f1| f1 << 'This is file 2.' }
end
You can use the same interface to read a ZIP file. Here's a method that uses the equivalent of Dir#foreach to recursively print out the contents of a ZIP file:
def process_zipfile(zip, path='')
if zip.file.file? path
puts %{#{path}: "#{zip.read(path)}"}
else
unless path.empty?
path += '/'
puts path
end
zip.dir.foreach(path) do |filename|
process_zipfile(zip, path + filename)
end
end
end
And here it is running against the
ZIP file I just created:
Zip::ZipFile.open('zipfile.zip') do |zip|
process_zipfile(zip)
end
# subdirectory/
# subdirectory/file2: "This is file 2."
# file1: "This is file 1."
Discussion
ZIP, or
PKZip, is the most popular compression format on Windows. As seen in the previous recipe, Unix separates the tasks of stuffing several files into a single archive (tar), and compressing the resulting file (gzip). On Windows,
ZIP files perform both tasks. If you want to compress a single file, you need to put it into a ZIP file all by itself.
The
rubyzip library provides several interfaces for creating and reading ZIP files. Zip::ZipFileSystem is the easiest for most programmers: in the example above, zip.file has about the same interface as the File class, and zip.dir is similar to the Dir class. The analogy holds because a ZIP file actually contains a tiny filesystem inside it.
If you're porting Java code, or you're already familiar with Java's java.util.zip library, you might prefer the Zip::ZipFile class. It more or less duplicates Java's ZipFile class in a Ruby idiom. Here it is being used to create the same ZIP file I created in the Solution:
Zip::ZipFile.open('zipfile2.zip', Zip::ZipFile::CREATE) do |zip|
zip.get_output_stream('file1') { |f| f << 'This is file 1.' }
zip.mkdir('subdirectory')
zip.get_output_stream('subdirectory/file2') { |f| f << 'This is file 2.' }
end
See Also
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