Command line argument parsing for simple applications.

Clap is a small library that can be bundled with your command line application. It covers the simple case of executing code based on the flags or parameters passed.

Using Clap is simple: just pass ARGV and a hash of flags, and it will extract the arguments as needed.

Clap.run ARGV,
  "-a" => lambda { |param| ... },
  "-b" => lambda { ... }

To better illustrate the usage, in the following examples ARGV is replaced by an array of strings.

If you want your command line application to require a file or display a version number, you can configure it like this:

Clap.run %w(-r foo -v),
  "-r" => lambda { |file| require file },
  "-v" => lambda { puts VERSION }

This will detect the -r or -v flags and act accordingly. Note that it will also read the necessary number of parameters for each flag based on the arity of the passed lambda.

Another example, for an application that takes a -v flag and also a list of files:

files = Clap.run %w(-v foo bar),
  "-v" => lambda { puts VERSION }

files == %w(foo bar)

If you prefer to group the options in a module or class, you can still attach the methods to command line flags:

class MyApp
  module CLI
    def self.version
      puts VERSION
    end

    def self.help(command)
      puts HELP[command]
    end
  end
end

Clap.run %w(-v -h foo),
  "-v" => MyApp::CLI.method(:version),
  "-h" => MyApp::CLI.method(:help)

When in doubt, check the tests for the different use cases.

$ gem install clap

Copyright (c) 2010 Michel Martens

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