Ruby is the command-line program being run, -e is called a flag, and "puts RUBY_VERSION" is the value given for the flag. The -e argument tells Ruby to run the provided code and exit. Clint is an alternative Ruby command line argument parser that's very good for programs using the subcommand pattern familiar from git(1), svn(1), apt-get(8), and many others. books = {} books [: matz] = "The Ruby Programming Language" books [: black] = "The Well-Grounded Rubyist" Hashes are also commonly used as a way to have named parameters in functions. Arrays are not the only way to manage collections of variables in Ruby.Another type of collection of variables is the hash, also called an associative array.A hash is like an array in that it's a variable that stores other variables. In addition, it separates option declarations from usage and help messages becuase the author feels like that's a better idea. But Ruby is far more than a web language. In your Ruby programs, you can access any command-line arguments passed by the shell with the ARGV special variable.ARGV is an Array variable which holds, as strings, each argument passed by the shell. So it’s now deprecated in Ruby 2.7 and will be removed in Ruby 3. dup if argv . method to parse command line arguments into an options hash, like this: options = {} option_parser.parse! # File lib/optparse.rb, line 1421 def permute ( * argv ) argv = argv [ 0 ]. When I run the above on the command line, I get back 2.4.0 printed out to standard output (which simply shows on the next line). The output is: Bob's name is bob Bob's height is 6 ft Bob's weight is 160 lbs Bob's hair is brown Hashes as Optional Parameters size == 1 and Array === argv [ 0 ] permute! How to Use Command-Line Arguments . Ruby Language Iterating Over a Hash Example A Hash includes the Enumerable module, which provides several iteration methods, such as: Enumerable#each , Enumerable#each_pair , Enumerable#each_key , and Enumerable#each_value . Because the automatic conversion is sometimes too complex and troublesome as described in the final section. (into: options) The ARGV array will be modified destructively, and any remaining arguments that aren’t options will be left in the array. $ ruby command_line_argv_check_length.rb one Too few arguments $ ruby command_line_argv_check_length.rb one two Working on ["one", "two"] Values received on the command line are strings In this snippet of code we first check if we got exactly 2 parameters … Ruby has a rich set of tools for shell scripting and text processing. The article consists of two main parts: building the command line application and making it available via Homebrew. Let's start by executing a Ruby command. The goal of this article is to show you how you can create your command line application using the Ruby programming language and make it available via Homebrew, so anyone can install it quickly and use in seconds. Parses command line arguments argv in permutation mode and returns list of non-option arguments. Note that no brackets are used below. If a hash is the last argument on a method call, no braces are needed, thus creating a really clean interface: In this case, Ruby’s flag -e means to execute the following as Ruby code. $ ruby -e 'puts "Hello, world."' With the options defined you can then use the OptionParser#parse! Ruby is strongly identified with Rails and web development. Run this program at the command line with ruby iterating_over_hashes.rb to see the results. Hello, world. In Ruby 2, keyword arguments can be treated as the last positional Hash argument and a last positional Hash argument can be treated as keyword arguments. 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