Little bit color

 0 #000000  1 #800000  2 #008000  3 #808000  4 #000080  5 #800080  6 #008080
 8 #808080  9 #ff0000 10 #00ff00 11 #ffff00 12 #0000ff 13 #ff00ff 14 #00ffff

 16 #000000  17 #00005f  18 #000087  19 #0000af  20 #0000d7  21 #0000ff
 22 #005f00  23 #005f5f  24 #005f87  25 #005faf  26 #005fd7  27 #005fff
 28 #008700  29 #00875f  30 #008787  31 #0087af  32 #0087d7  33 #0087ff
 34 #00af00  35 #00af5f  36 #00af87  37 #00afaf  38 #00afd7  39 #00afff
 40 #00d700  41 #00d75f  42 #00d787  43 #00d7af  44 #00d7d7  45 #00d7ff
 46 #00ff00  47 #00ff5f  48 #00ff87  49 #00ffaf  50 #00ffd7  51 #00ffff

Useful keys for - Console, Tmux

CONSOLE Cmd Action a on the beginning u delete all line w delete previous word xx select line i insert tab e edit line h like backspace j like enter k delete to the end l clear screen and live line comnand b move right f move left r search in history

TMUX tmux new -s session-name tmux attach-session -t shared-session Ctrl+b+: Cmd Action w List window s List sessions c Create a new window x Close widnow n Change to next window p Change to previous window " Split pane horizontally % Split pane vertically , Rename current window o Move to next pane d Deatach session [ Start read mod

Array

var = Array(1) # => [1]
var = *1       # => [1]

# * is the same as Array

var = Array([1,2,3]) #=> [1,2,3]
var = *[1,2,3]       #=> [1,2,3]

# its useful when we need array like
var = [var] unless var.is_a? Array
var = [var].flatten

# we can write
var = *var     # => [var]
# but can't
*var           # => syntax error

Ruby Include and Extend

module Base
  def print
    p 'base'
  end
end

class A
  # add method for instance
  include Base
end

A.new.print


class B
  # add method for class
  extend Base
end

B.print

class C
  # include module for singleton
  # the same like extend
  class << self
    include Base
  end
end

C.print

include work the same as inheritance but its not the same:

1. class have only one parent
2. include extend only instance

# check include
A.new.kind_of? Base #=> true

# check extend
B.kind_of? Base #=> true

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... code
</pre>

Vim

Ruby singleton

# All is Object
# =============
#
# print - is singleton method for instance

instance = Document.new
def instance.print
end

class << instance
  def print; end
end

# print - is singleton method for Document
# Document - is instance too of Class object

def Document.pring
end

class Document
  class << self
    def print; end
  end
end