JohnAllen.us

Merry Christmas!!
I love the ability that Ruby has to extend common value types and add my own personal methods.  One that I use alot is a simple ‘Hexdump’ method for the String class:

#!/usr/bin/ruby

class String

  def hexdump
    i = 1
    rr = ""
    while (self.length > 16*(i-1))
      a=self.slice(16*(i-1)..(16*i)-1)
      rr += sprintf("%06x: %4.4x %4.4x %4.4x %4.4x   %4.4x %4.4x %4.4x %4.4x ", (i-1)*16,  *a.unpack("n16"))
      rr += sprintf("|%s|\n", a.tr("^\040-\176","."))
      i += 1
    end
    return rr
  end

end

if __FILE__ == $0
   infile = File.new(ARGV[0], "r")
   ff = infile.read
   infile.close
   puts ff.hexdump
end
exit

The first part extends the String class, adding the ‘hexdump’ method. Calling this method on any string will return a dump of the string in hex. Its patterned after a very old BASIC program I used long ago. The bottom part of the code implements a file hexdump program:

 john@Orb:~/Dev/Ruby$ ./hexdump.rb /etc/rc.local
000000: 2321 2f62 696e 2f73   6820 2d65 0a23 0a23 |#!/bin/sh -e.#.#|
000010: 2072 632e 6c6f 6361   6c0a 230a 2320 5468 | rc.local.#.# Th|
000020: 6973 2073 6372 6970   7420 6973 2065 7865 |is script is exe|
000030: 6375 7465 6420 6174   2074 6865 2065 6e64 |cuted at the end|
000040: 206f 6620 6561 6368   206d 756c 7469 7573 | of each multius|
000050: 6572 2072 756e 6c65   7665 6c2e 0a23 204d |er runlevel..# M|
000060: 616b 6520 7375 7265   2074 6861 7420 7468 |ake sure that th|
000070: 6520 7363 7269 7074   2077 696c 6c20 2265 |e script will "e|
000080: 7869 7420 3022 206f   6e20 7375 6363 6573 |xit 0" on succes|
000090: 7320 6f72 2061 6e79   206f 7468 6572 0a23 |s or any other.#|
0000a0: 2076 616c 7565 206f   6e20 6572 726f 722e | value on error.|
0000b0: 0a23 0a23 2049 6e20   6f72 6465 7220 746f |.#.# In order to|
0000c0: 2065 6e61 626c 6520   6f72 2064 6973 6162 | enable or disab|
0000d0: 6c65 2074 6869 7320   7363 7269 7074 206a |le this script j|
0000e0: 7573 7420 6368 616e   6765 2074 6865 2065 |ust change the e|
0000f0: 7865 6375 7469 6f6e   0a23 2062 6974 732e |xecution.# bits.|
000100: 0a23 0a23 2042 7920   6465 6661 756c 7420 |.#.# By default |
000110: 7468 6973 2073 6372   6970 7420 646f 6573 |this script does|
000120: 206e 6f74 6869 6e67   2e0a 0a65 7869 7420 | nothing...exit |
000130: 300a 0000 0000 0000   0000 0000 0000 0000 |0.|