merging similar hashes in ruby?

Question

I've tried and tried, but I can't make this less ugly/more ruby-like. It seems like there just must be a better way. Help me learn.

class Df
  attr_accessor :thresh
  attr_reader :dfo

  def initialize
      @dfo    = []
      @df     = '/opt/TWWfsw/bin/gdf'

      case RUBY_PLATFORM
      when /hpux/i
          @fstyp = 'vxfs'
      when /solaris/i
          # fix: need /tmp too
          @fstyp = 'ufs'
      when /linux/i
          @df = '/bin/df'
          @fstyp = 'ext3'
      end
      @dfo  = parsedf
  end
  def parsedf
      ldf = []
      [" "," -i"] .each do |arg|
          fields = %w{device size used avail capp mount}
          fields = %w{device inodes inodesused inodesavail iusep mount} if arg == ' -i'
          ldf.push %x{#{@df} -P -t #{@fstyp}#{arg}}.split(/\n/)[1..-1].collect{|line| Hash[*fields.zip(line.split).flatten]}
      end
      out = []
      # surely there must be an easier way
      ldf[0].each do |x|
          ldf[1].select { |y|
              if y['device'] == x['device']
                  out.push x.merge(y)
              end
          }
      end
      out
  end
end

Answer 1

In my machine, your ldf array after the df calls yields the following:

irb(main):011:0> ldf
=> [[{"device"=>"/dev/sda5", "size"=>"49399372", "mount"=>"/", "avail"=>"22728988", "used"=>"24161036", "capp"=>"52%"}], [{"device"=>"/dev/sda5", "inodes"=>"3137536", "mount"=>"/", "iusep"=>"13%", "inodesavail"=>"2752040", "inodesused"=>"385496"}]]

The most flexible approach to merging such a structure is probably something along these lines:

irb(main):013:0> ldf.flatten.inject {|a,b| a.merge(b)}
=> {"device"=>"/dev/sda5", "inodes"=>"3137536", "size"=>"49399372", "mount"=>"/", "avail"=>"22728988", "inodesavail"=>"2752040", "iusep"=>"13%", "used"=>"24161036", "capp"=>"52%", "inodesused"=>"385496"}

Some ruby programmers frown on this use of inject, but I like it, so your mileage may vary.

As for helping making your code more ruby like, I suggest you talk to some experienced rubyist you might know over your code to help you rewriting it in a way that follows good style and best practices. Probably that would the preferable than to just have someone rewrite it for you here.

Best of Luck!

Answer 2

Didn't test the code, but here goes:

ARGUMENTS = {
  " "   => %w{size used avail capp mount},
  " -i" => %w{inodes inodesused inodesavail iusep mount}
}

def parsedf
  # Store resulting info in a hash:
  device_info = Hash.new do |h, dev|
    h[dev] = {} # Each value will be a empty hash by default
  end

  ARGUMENTS.each do |arg, fields|
    %x{#{@df} -P -t #{@fstyp}#{arg}}.split(/\n/)[1..-1].each do |line|
      device, *data = line.split
      device_info[device].merge! Hash[fields.zip(data)]
    end
  end
  device_info
end

Notes: returns something a bit different than what you had:

{ "/dev/sda5" => {"inodes" => "...", ...},
  "other device" => {...}
}

Also, I'm assuming Ruby 1.8.7 or better for Hash[key_value_pairs], otherwise you can resort to the Hash[*key_value_pairs.flatten] form you had

Depending on your needs, you should consider switch the fields from string to symbols; they are the best type of keys.

Finally, I'd recommend using http://refactormycode.com or similar for that type of question, since it's unlikely to help many people.