hyfather

M stands for the Meta key. Commonly represented by the Alt/Option/Esc key on your keyboard.
C stands for the Control key.
Example -- C-k means 'hit k while keeping Control pressed.'

M-.
Yank the last argument to the previous command.

M-C-y
Yank the first argument to the previous command.

hyfather

[{:a => 'alpha'}, {:b => 'beta'}, {:c => 'charlie'}].map(&:to_a)
#=> [[[:a, "alpha"]], [[:b, "beta"]], [[:c, "charlie"]]]

flat_array = [{:a => 'alpha'}, {:b => 'beta'}, {:c => 'charlie'}].map(&:to_a).flatten
#=> [:a, "alpha", :b, "beta", :c, "charlie"]

Hash[*flat_array]
#=> {:a=>"alpha", :b=>"beta", :c=>"charlie"}

hyfather

lambda{|*args| args}.call(1, 2)
#=> [1, 2]
# This is the splat operator used in the 'collecting mode'.
# The splat before the args ensured that all arguments were marshalled into an Array.

[1, 2, [3, 4]]
#=> [1, 2, [3, 4]] 
[1, 2, *[3, 4]]
#=> [1, 2, 3, 4] 
# This is the unmarshalling 'mode' of the splat operator.

hyfather

[:a, :b, :c].map {|e| e.to_s }
#=> ['a', 'b', 'c'] # Invoke .to_s on each element and collect these in an array.

[:a, :b, :c].map(&:to_s)
#=> ['a', 'b', 'c'] # The same result obtained in a shorthand fashion.

hyfather

{:a => 'alpha'}.to_a
#=> [[:a, "alpha"]] # Notice the nested array

Hash[:a => 'alpha']
#=> {:a => 'alpha'}

Hash[[:a => 'alpha']]
#=> {} # Doesn't work with a nested array.

Hash[[[:a => 'alpha']]]

hyfather

class Array
  def flatten_hashes
    Hash[*self.map(&:to_a).flatten]
  end
end

[{:a => 'alpha'}, {:b => 'beta'}, {:c => 'charlie'}].flatten_hashes
#=> {:a => 'alpha', :b => 'beta', :c => 'charlie'}

hyfather

git log HEAD^..HEAD --format="%an pushed change %h on %aD.%n%nWhat's in this change?%n%s%n"

hyfather

#!/usr/bin/env sh
# Copy public key to authorized_keys of a remote machine
if [ -z $1 ];then
    echo "Usage"
    echo "ssh-copy-id hostname /path/to/public/key"
    exit
fi

if [ -z $2 ]; then
KEYCODE=`ssh-add -L`