Vidul Nikolaev Petrov: Category Ruby

Sequence Types and Slice

root — Tue, 21 Oct 2008 05:08:00 -0600

Ruby slice:

a = [1, 2, 3, 4, 5, 6]
a[0..-1] # [1, 2, 3, 4, 5, 6]
a[(0..-1)] # tha same

Python slice:

a = [1, 2, 3, 4, 5, 6]
a[:-1] # [1, 2, 3, 4, 5]
a[:] # [1, 2, 3, 4, 5, 6]
a[0:len(a):2] # [2, 4, 6]  Nice, isn't it?

Quick Scanner (Host/Port)

root — Sun, 28 Sep 2008 13:09:00 -0600

#!/usr/bin/ruby

host_port = ARGV[0]
host = host_port.split(':').first
port = host_port.split(':').last

puts %x[nmap -p #{port} #{host}]

Or just:

#!/usr/bin/ruby

host, port = ARGV[0].split(':')

puts %x[nmap -p #{port} #{host}]

Usage (cli and given that the script is named scan_proxy):

./scan_proxy 202.105.182.87:808

Simple Phonebook Script

root — Sat, 20 Sep 2008 08:39:00 -0600


#!/usr/bin/env ruby

class Hash
  def search(arg)
    self.select { |k,v| k =~ /#{arg}/ or v =~ /#{arg}/ }
  end
end

search = ARGV[0]
search =~ /^[0-9]+/ and search = search.to_i

phones = {
  "me"        => "359880101020406",
  "Hitler"     => "+49 666",
  "Van Gog" => "+31",
  "devil"      => "666",
  "God"       => "1",
}

phones.search(search).each do |person|
  print "person:#{person.first}\tnumber:#{person.last}\n"
end

Ruby DATA (embedded data)

root — Fri, 22 Aug 2008 10:04:00 -0600

module Kernel
  RE_THIS_DATA = lambda{ |number| /^__DATA#{number}__\n/ }
  RE_THE_DATA  = /^__DATA\d+__/

  def __data__(num="")
    data = File.read($0).split(RE_THIS_DATA.call(num))
    data[1].split(RE_THE_DATA)[0] if data[1]
  end
end

puts "DATA"
print __data__()

puts "DATA1"
print __data__(1)

puts "DATA2"
print __data__(2)

__END__

__DATA__
data_1
data_2
data_3

__DATA1__
data1_1
data1_2
data1_3

data1_11

__DATA2__
data2_1
data2_2
data2_3

data2_31

Chdir Method with Block

root — Fri, 22 Aug 2008 09:13:00 -0600

# temporary changes the cwd to '/tmp',
# adds content to a file and finally restores cwd

p Dir.getwd

Dir.chdir("/tmp") do
  p Dir.getwd
  File.open("test.txt", "a") do |f|
    f << Time.now << "\n"
  end
end

p Dir.getwd

Random strings

root — Tue, 19 Aug 2008 07:06:00 -0600

module Kernel
  def random_uc(size=16)
    Array.new(size){ rand(26)+65 }.pack('C*')
  end
  def random_lc(size=16)
    Array.new(size){ rand(26)+97 }.pack('C*')
  end
  def random_num(size=16)
    Array.new(size){ rand(10) }.join
  end
end

random_uc => "HRTWYJBJEZDKYPTJ"
random_lc => "onxkvkezqukspmcx"
random_num => "5862195932579950"

Active Support Date and Time

root — Sun, 10 Aug 2008 07:38:00 -0600

n = Time.now

(n.at_end_of_week - n.at_beginning_of_week) / (24 * 3600)

# 6.99998842592593

Shouldn’t it be 7 exactly?

Probably because the start of a week is 00:00:00 and the end is 23:59:59:

>> Time.now.at_beginning_of_week
=> Mon Aug 04 00:00:00 +0300 2008

>> Time.now.at_end_of_week
=> Sun Aug 10 23:59:59 +0300 2008

Setting Core Objects' Methods in RoR

root — Sat, 09 Aug 2008 06:14:00 -0600

mkdir -p RAILS_ROOT/vendor/plugins/core_methods
mkdir -p RAILS_ROOT/vendor/plugins/core_methods/init.rb

The content of init.rb:

module Rails

  empty_and_nil = %q{def empty_and_nil; self.empty?? nil : self end}

  Array.send :class_eval, empty_and_nil
  Hash.send  :class_eval, empty_and_nil

end

The namespace Rails isn’t necessary, it’s a cosmetic feature.

Getting the Weekday

root — Sat, 09 Aug 2008 03:50:00 -0600

# if the birthdate is 1978-12-03

Time.gm(1978, 12, 3).strftime("%a") 
Time.gm(1978, 12, 3).strftime("%A") 

# the weekday day is "Sun" (%a), "Sunday" (%A)

Ruby core docs

Return nil Instead Of empty Array instance

root — Fri, 08 Aug 2008 04:35:00 -0600

class Array
  def empty_and_nil
    self.empty?? nil : self
  end
end

result = [1,2,3].empty_and_nil # [1, 2, 3]
result = [].empty_and_nil        # nil

How false Is nil

root — Mon, 04 Aug 2008 07:59:00 -0600

Use nil when the return is a boolean value.
Use false when the return is either false or not true object.
Otherwise they have pretty much the same semantic:

nil == false => false
nil.nil?        => true
false.nil?     => false
true.nil?      => false

if !nil && !false
  puts 'true'
end

if nil.nil? && !true.nil?
  puts 'true'
end

>> TrueClass.ancestors
=> [TrueClass, Object, Kernel]
>> FalseClass.ancestors
=> [FalseClass, Object, Kernel]
>> NilClass.ancestors
=> [NilClass, Object, Kernel]

Ruby core docs

Multiplication Table In AoH Structure

root — Sun, 03 Aug 2008 12:09:00 -0600

mt = Array.new(10) { |e| Hash.new { |h,k| h[k] = k * e } }

mt[1][2] => 2
mt[2][2] => 4
mt[5][4] => 20
mt[9][5] => 45

Converting Between Numeric Bases

root — Thu, 31 Jul 2008 23:58:00 -0600

Sample .bashrc file:

# decimal to binary
alias d2b='ruby -e "puts ARGV.first.to_i.to_s(2)"'
# decimal to hexademical
alias d2h='ruby -e "puts ARGV.first.to_i.to_s(16)"'
# decimal to octal
alias d2o='ruby -e "puts ARGV.first.to_i.to_s(8)"'

# binary to decimal
alias b2d='ruby -e "puts eval(%q|0b| + ARGV.first)"'
# binary to hexademical
alias b2h='ruby -e "puts eval(%q|0b| + ARGV.first).to_s(16)"'
# binary to octal
alias b2o='ruby -e "puts eval(%q|0b| + ARGV.first).to_s(8)"'

# hexademical to decimal
alias h2d='ruby -e "puts eval(%q|0x| + ARGV.first)"'
# hexademical to binary
alias h2b='ruby -e "puts eval(%q|0x| + ARGV.first).to_s(2)"'
# hexademical to octal
alias h2o='ruby -e "puts eval(%q|0x| + ARGV.first).to_s(8)"'

# octal to decimal
alias o2d='ruby -e "puts eval(%q|0o| + ARGV.first)"'
# octal to binary
alias o2b='ruby -e "puts eval(%q|0o| + ARGV.first).to_s(2)"'
# octal to hexademical
alias o2h='ruby -e "puts eval(%q|0o| + ARGV.first).to_s(16)"'

Google::Translate, A Simple API In Ruby

root — Thu, 31 Jul 2008 05:03:00 -0600

require 'rubygems'
require 'google_translate'

tr = Google::Translate.new

# from English to German
tr.translate :from => "en", :to => "de", :text => "Hello, World!"
 => Hallo, Welt!

# from English to Spanish
tr.translate :from => "en", :to => "es", :text => "Hello, World!"
 => Hola, Mundo!

# WWW::Mechanize constructor usage
tr = Google::Translate.new { |agent| agent.user_agent_alias = 'Mac Safari' }

The project home page

String Substitution

root — Wed, 30 Jul 2008 07:59:00 -0600

require 'benchmark'

n = 1_000_000
s = " : : : "

Benchmark.bm do |x|
  x.report("tr:")   { n.times{ s.tr(":", ";") } }
  x.report("tr_s:") { n.times{ s.tr_s(":", ";") } }
  x.report("gsub:") { n.times{ s.gsub(":", ";") } }
end

Right, tr beats the other methods:

    user     system      total        real
tr:  2.760000   0.120000   2.880000 (  2.897022)
tr_s:  5.310000   0.240000   5.550000 (  5.822026)
gsub:  8.850000   0.200000   9.050000 (  9.311452)

Google Translation API for Ruby

root — Sun, 27 Jul 2008 05:47:00 -0600

In essence (from bulgarian to japanese):

  agent = WWW::Mechanize.new
  agent.post("http://translate.google.com/translate_t", 
    "sl" => "bg", 
    "tl" => "ja", 
    "text" => "Здравей, свят!").search("#result_box").inner_html

results in こんにちは、世界！

three ways to print the alphabet

root — Sun, 27 Jul 2008 01:55:00 -0600

String methods:

"a".upto("z"){ |i| puts i }

a = String.new "a"
0.upto(0){ p a }
1.upto(25){ p a.next! }

Range method:

("a".."z").each{ |e| puts e }

def and undef a method

root — Fri, 25 Jul 2008 22:50:00 -0600

  def my_method; end # define a method
  undef my_method    # remove a method

The core manual

Ugly join implementation

root — Fri, 25 Jul 2008 22:11:00 -0600

 arr = (1..10).to_a

 str = arr * ', '
 str = arr.join(', ')

Am I going to use the perlish coding style? Not really.

Simple File Manipulation

root — Mon, 21 Jul 2008 16:15:00 -0600

Ruby file manipulation is as easy as:

  MyFile.create "test.txt"
  MyFile.add "test.txt", "some content"
  MyFile.remove "test.txt"

For example create a file caled fileeasy.rb and add the following module to it:

module FileEasy

  def self.included(subject)
    subject.extend(ClassMethods)
  end

  module ClassMethods
   alias_method :delete, :remove
   alias_method :unlink, :remove

    def create(filename)
      File.open(filename, "w")
    end
    def add(filename, text)
      File.open(filename, "a"){ |f| f << text }
    end
    def remove(filename)
      File.delete(filename)
    end
  end

end

Then test it with irb:

require 'fileeasy'

class MyClass
  include FileEasy
end

MyFile.create "text.txt"
MyFile.add "text.txt", "test content"
MyFile.remove "text.txt"

Of course this post is just a simple tutorial and the standard library is the best choice – FileUtils.