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# http://ruby-doc.org/core-2.5.0/IO.html#method-i-gets
# Ruby >= 2.4

irb(main):001:0> gets(chomp: true)
hello world
=> "hello world"

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require 'ipaddr'
IPAddr.new("172.16.0.0/12").private?
=> true

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SecureRandom.alphanumeric
=> "i2jZWXwSN4123yk2"

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str = "- hello world -"
str.delete_prefix("- ")
=> "hello world -"

str.delete_suffix(" -")
=> "- hello world"

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'- Do you know whether this string'.start_with?(/^- /)
=> true

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Integer.sqrt(24)
=> 4

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h = { a: 1, b: 2, c: 3 }
=> {:a=>1, :b=>2, :c=>3}

h.transform_keys {|k| k.to_s }
=> {"a"=>1, "b"=>2, "c"=>3}

h.transform_keys(&:to_s)
=> {"a"=>1, "b"=>2, "c"=>3}

h.transform_keys.with_index {|k, i| "#{k}.#{i}" }

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%w[ant bear cat].all?(/t/)
=> false

[1, 2i, 3.14].all?(Numeric) 
=> true

[1, 2, 3].all?(1..3)
=> true

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Dir.glob("*", base: "/lib")
=> ["x86_64-linux-gnu", "cpp", "init", "terminfo", "systemd", "lsb", "udev"]

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[1, 2, 3].append(4)
=> [1, 2, 3, 4]

[1, 2, 3].prepend(0)
=> [0, 1, 2, 3]