The article consists of two main parts: building the command line application and making it available via Homebrew. 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 $ ruby -e 'puts "Hello, world."' The -e argument tells Ruby to run the provided code and exit. Ruby is strongly identified with Rails and web development. Note that no brackets are used below. 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. 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. Hello, world. If a hash is the last argument on a method call, no braces are needed, thus creating a really clean interface: So it’s now deprecated in Ruby 2.7 and will be removed in Ruby 3. How to Use Command-Line Arguments . Ruby is the command-line program being run, -e is called a flag, and "puts RUBY_VERSION" is the value given for the flag. With the options defined you can then use the OptionParser#parse! Let's start by executing a Ruby command. In addition, it separates option declarations from usage and help messages becuase the author feels like that's a better idea. # File lib/optparse.rb, line 1421 def permute ( * argv ) argv = argv [ 0 ]. Parses command line arguments argv in permutation mode and returns list of non-option arguments. 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. 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. 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). dup if argv . Ruby has a rich set of tools for shell scripting and text processing. In this case, Ruby’s flag -e means to execute the following as Ruby code. size == 1 and Array === argv [ 0 ] permute! method to parse command line arguments into an options hash, like this: options = {} option_parser.parse! Run this program at the command line with ruby iterating_over_hashes.rb to see the results. But Ruby is far more than a web language. $ 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 … Because the automatic conversion is sometimes too complex and troublesome as described in the final section. 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 . 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