disk_free_space

• This function’s solution assumes a Unix-like operating system.

  The disk_free_space function in PHP will return the number of bytes remaining on the filesystem containing a given directory.

  PHP

  $bytes = disk_free_space('/');
  print $bytes;
   
  //=> 1048576

  Ruby does not have an equivalent method and the Ruby Standard Library also does not provide an easy way to get this same information.

  Scraping the output of df

  On Unix-like systems, the df shell command returns this same information. One solution is to scrape the output of df into a form that’s easier to use in Ruby.

  Ruby

  class DiskReporter
    def self.usage(path='/')
      arg = "'#{path.gsub "'", "\\\\'"}'"
      header, stats = `df -P #{arg}`.split(/\n/)
   
      # sanity check on df posix output
      posix = /Filesystem\s+(\d+)-blocks\s+Used\s+Avail(?:able)*\s+Capacity\s+Mount/
      header_matches = posix.match(header)
      return false unless header_matches
   
      # split stats and check for expected results length
      stats = stats.split(/\s+/, 6) unless stats.nil?
      return false if stats.nil? || stats.size != 6
   
      # calculate percent free/used on this filesystem
      percent_used = stats[4].match(/(\d+)%/)[1].to_i
      percent_free = (100 - percent_used)
   
      {
       :block_size   => header_matches[1].to_i,
       :filesystem   => stats[0],
       :blocks_total => stats[1].to_i,
       :blocks_used  => stats[2].to_i,
       :blocks_avail => stats[3].to_i,
       :percent_used => percent_used,
       :percent_free => percent_free,
       :mounted_on   => stats[5]
      }
    end
  end
  

  When DiskReporter.usage is called, it will return a Hash containing the information returned by the df command.

  Ruby

  require 'diskreporter'
   
  usage = DiskReporter.usage('/path/to/foo')
   
  p usage
  #=> {:filesystem=>"/dev/disk0s2", :blocks_total=>194699744, 
  #    :blocks_used=>142675528, :percent_used=>73, 
  #    :blocks_avail=>51512216, :percent_free=>27, 
  #    :mounted_on=>"/", :block_size=>512}
   
  p usage[:percent_free]
  #=> 27

  It’s worth noting that the PHP’s disk_free_space only results in a single system call, while this solution launches a process with the df command.

  This is a more expensive operation, making this solution best for command line scripts and not for during the HTTP request of a Rails application.

  see also

  • disk_total_space
  • flush

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