Options are defined using the #opt or #option methods. They can then be used from the command line with a short and/or long name. For instance

opt :v, :version

Creates an Option which can be used with -v or --version. Options should also be given a description so you know what they do! You can either pass a string with the description to #opt(ion);

opt :v, :version, 'Display current version'

or call #desc before defining the Option,

desc 'Display current version'
opt :v, :version

Options with names containing underscores are callable with dashes replacing the underscores, as well as with underscores.

opt :longer_than_expected
# can use  --longer-than-expected
#     and  --longer_than_expected

Blocks

Options can be passed a block when defined. The block is then executed when the Option is used.

opt :hello do
  puts 'Hello'
end

They can also be given arguments (read the Arguments section for more details).

opt :hello, arg: '<name>' do |name|
  puts "Hello #{name}"
end

The arguments are then passed to the block. It's possible to have multiple arguments, including optional arguments.

opt :hello, arg: '<first> [<last>]' do |first, last|
  puts ["Hello", first, last].compact.join(' ')
end

# --hello John
#=> "Hello John"

# --hello John Doe
#=> "Hello John Doe"

If an expected argument is not given an error is raised detailing the problem. Using the previous example,

$ clive_test --hello
Clive::Parser::MissingArgumentError: missing 
  argument for --hello, found [], needed 
  <first> [<last>]