From: John Carter <john.carter@...>
Date: 2009-03-30T13:19:35+09:00
Subject: Re: Is there a ruby way to get the disk size of a directory?

On Mon, 30 Mar 2009, Juan Zanos wrote:

> I was wondering if there was something to du -h?

Umm, it's pretty ugly what I do have... it invokes the Linux statfs
system call...

$ irb -r StatFs64.rb 
irb(main):001:0> a = StatFs64.new( "/home")
=> #<StatFs64:0xb7cd8108 @statfs64={"f_spare0"=>0, "f_spare1"=>0, "f_files"=>5750784, "f_bfree"=>3332642, "f_bsize"=>4096, "f_spare2"=>0, "f_blocks"=>11299984, "f_spare3"=>0, "f_spare4"=>0, "f_ffree"=>4574344, "f_fsid0"=>1992275371, "f_fsid1"=>157862524, "f_frsize"=>4096, "f_namelen"=>255, "f_bavail"=>2758620, "f_type"=>61267}>
irb(main):002:0> p a.free_gigabytes
10.5233001708984
=> nil



John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand

----------------------------------------------------------------------
=begin rdoc
This stuff can depend on the exact version of linux you have.
Ugly, I know.

__extension__ typedef unsigned long long int __u_quad_t;
__extension__ typedef __u_quad_t __fsblkcnt64_t;
__extension__ typedef __u_quad_t __fsfilcnt64_t;
__extension__ typedef struct { int __val[2]; } __fsid_t;

struct statfs64
   {
     int f_type;
     int f_bsize;
     __fsblkcnt64_t f_blocks;
     __fsblkcnt64_t f_bfree;
     __fsblkcnt64_t f_bavail;
     __fsfilcnt64_t f_files;
     __fsfilcnt64_t f_ffree;
     __fsid_t f_fsid;
     int f_namelen;
     int f_frsize;
     int f_spare[5];
   };

#define __NR_statfs64		268
#define __NR_fstatfs64		269

I dug the above info out using the follow trick....
tmp = "/tmp/struct.c"
open(tmp, 'w') do |c|
   c.puts "
#define _GNU_SOURCE 1
#include <sys/syscall.h>
#include <sys/statfs.h>

struct statfs64 s;

"
end

puts `gcc -E  #{tmp}`

=end

require 'pp'

class StatFs64
   STRUCT_STATFS64 = [
                      [0, 'i', 'f_type'],
                      [0, 'i', 'f_bsize'],
                      [0, 'Q', 'f_blocks'],
                      [0, 'Q', 'f_bfree'],
                      [0, 'Q', 'f_bavail'],
                      [0, 'Q', 'f_files'],
                      [0, 'Q', 'f_ffree'],
                      [0, 'i', 'f_fsid0'],
                      [0, 'i', 'f_fsid1'],
                      [0, 'i', 'f_namelen'],
                      [0, 'i', 'f_frsize'],
                      [0, 'i', 'f_spare0'],
                      [0, 'i', 'f_spare1'],
                      [0, 'i', 'f_spare2'],
                      [0, 'i', 'f_spare3'],
                      [0, 'i', 'f_spare4'],
                     ]

   def syscall_pack( triplets)
     template = ''
     default = []
     triplets.each do |value, directive, name|
       default << value
       template += directive
     end
     default.pack( template)
   end

   def syscall_unpack( triplets, string)
     template = ''
     names = []
     triplets.each do |value, directive, name|
       names << name
       template += directive
     end

     result = {}
     values = string.unpack( template)
     names.each_with_index do |name,i|
       value = values[i]
       result[name] = value
     end

     result
   end

   def initialize( path)
     string = syscall_pack( STRUCT_STATFS64)
     result = syscall( 268, path, string.size, string)
     raise "Unexpected return value '#{result}'" unless
       result == 0

     @statfs64 = syscall_unpack( STRUCT_STATFS64, string)
   end

   def free_megabytes
     (@statfs64['f_bavail'] * @statfs64['f_bsize']) / (1024 * 1024.0)
   end

   def free_gigabytes
     free_megabytes / 1024.0
   end

   attr_reader :statfs64
end