From: "Matthew B." <mebloch@...>
Date: 2010-11-20T04:30:36+09:00
Subject: Re: Is there a ruby way to get the disk size of a directory?

For the web archive :) my slightly shorter effort, possibly more 
portable, is attached.  It relies on libffi being installed:

module Linux; module StatFs

  # The result of a statfs operation, see "man statfs" for more 
information
  # on each field.  We add some helper methods that deal in bytes.
  #
  class Result < Struct.new(:type, :bsize, :blocks, :bfree, :bavail,
                            :files, :ffree)
    def total; blocks * bsize; end
    def free; bfree * bsize; end
    def avail; bavail * bsize; end
  end

  module Lib
    extend FFI::Library
    ffi_lib FFI::Library::LIBC
    attach_function 'statfs64', [:string, :pointer], :int
  end

  # Drives the interface to the C library, returns a StatFs::Result 
object
  # to show filesystem information for the given path.
  #
  def self.statfs(path)
    output = FFI::MemoryPointer.new(128)
    begin
      error_code = Lib::statfs64(path, output)
      raise "statfs raised error #{error_code}" if error_code != 0
      return Result.new(*output[0].read_array_of_long(7))
    ensure
      output.free
    end
  end

end; end

I've only tested it to see that the results tally with "df", so e.g. to 
find the number of free bytes on your root, you run:

Linux::StatFs.statfs(".").free

Regards,

--
Matthew Bloch

-- 
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