Extract one or multiple archives of any type

gistfile1.rb

#!/usr/bin/env ruby

# check if a command exists
def command_exists?(command)
  system("which #{command} > /dev/null 2>/dev/null")
  $?.exitstatus == 0
end

def usage
  usage  = "Usage: extract [-vz] <file> [<file> <file> ..]\n\n"
  usage << "-v\tVerbose output. This option doesn't work will all the archive types\n"
end


def extract(file, verbose = false)
  parts = file.split('.')
  extension = parts.pop
  if (extension == "gz" || extension == "bz2") && parts.last == "tar"
    extension = parts.pop  + "." + extension
  end
  
  case extension
    when "tar.gz", "tgz"
      command = verbose ? "tar xvzf" : "tar xzf"
      system("#{command} #{file}") if command_exists?("tar")
    when "tar.bz2", "tbz2"  
      command = verbose ? "tar xvjf" : "tar xjf"
      system("#{command} #{file}") if command_exists?("tar")
    when "tar"
      command = verbose ? "tar xvf" : "tar xf"
      system("#{command} #{file}") if command_exists?("tar")
    when "bz2"
      command = verbose ? "bunzip2 -v" : "bunzip2"
      system("#{command} #{file}") if command_exists?("bunzip2")
    when "rar"
      system("unrar #{file}") if command_exists?("unrar")
    when "gz"
      command = verbose ? "gunzip -v" : "gunzip"
      system("#{command} #{file}") if command_exists?("gunzip")
    when "zip"
      command = verbose ? "unzip" : "unzip -q"
      system("#{command} #{file}") if command_exists?("unzip")
    when "Z"
      system("uncompress #{file}") if command_exists?("uncompress")
    when "7z"
      system("7z x #{file}") if command_exists?("7z")
    else
      false
  end
end

# ------------------------------------------------------------------------

extracted_file_list = []

if ARGV.empty?
  print usage
else
  # parse options
  verbose = ARGV.include?("-v")
  ARGV.delete("-v")
  
  ARGV.each do |file|
    if File.file?(file)
      sucess = extract file, verbose
      if sucess
        extracted_file_list << file
      else
        puts "#{file} cannot be extracted using this script..."
      end
    elsif File.directory?(file)
      puts "#{file} is a directory not an archive..."
    end
  end
end

# Show a nice exit message with the list of extracted archives
unless extracted_file_list.empty?
  puts "\nThe following archives have been extracted successfully:"
  extracted_file_list.each do |archive|
    puts "\t#{archive}"
  end
end