Docopt – command line option parser, that will make you smile

This is a detached fork of the original docopt.rb.

• For a drop-in replacement, simply require 'docopt_ng/docopt'
• Otherwise, use require 'docopt_ng' and DocoptNG instead of Docopt.

This is the ruby port of docopt, the awesome option parser written originally in python.

Isn't it awesome how optparse and argparse generate help messages based on your code?!

Hell no! You know what's awesome? It's when the option parser is generated based on the beautiful help message that you write yourself! This way you don't need to write this stupid repeatable parser-code, and instead can write only the help message--the way you want it.

docopt helps you create most beautiful command-line interfaces easily:

require "docopt_ng/docopt"

doc = <<DOCOPT
Naval Fate.

Usage:
  #{__FILE__} ship new <name>...
  #{__FILE__} ship <name> move <x> <y> [--speed=<kn>]
  #{__FILE__} ship shoot <x> <y>
  #{__FILE__} mine (set|remove) <x> <y> [--moored|--drifting]
  #{__FILE__} -h | --help
  #{__FILE__} --version

Options:
  -h --help     Show this screen.
  --version     Show version.
  --speed=<kn>  Speed in knots [default: 10].
  --moored      Moored (anchored) mine.
  --drifting    Drifting mine.

DOCOPT

begin
  pp Docopt.docopt(doc)
rescue Docopt::Exit => e
  puts e.message
  exit e.exit_code
end

Beat that! The option parser is generated based on the docstring above that is passed to docopt function. docopt parses the usage pattern (Usage: ...) and option descriptions (lines starting with dash "-") and ensures that the program invocation matches the usage pattern; it parses options, arguments and commands based on that. The basic idea is that a good help message has all necessary information in it to make a parser.

$ gem install docopt_ng

Docopt takes 1 required and 1 optional argument:

• doc should be a string that describes options in a human-readable format, that will be parsed to create the option parser. The simple rules of how to write such a docstring (in order to generate option parser from it successfully) are given in the next section. Here is a quick example of such a string:

    Usage: your_program.rb [options]
  
    -h --help     Show this.
    -v --verbose  Print more text.
    --quiet       Print less text.
    -o FILE       Specify output file [default: ./test.txt].
  

  The optional second argument contains a hash of additional data to influence docopt. The following keys are supported:

• help, by default true, specifies whether the parser should automatically print the usage-message (supplied as doc) in case -h or --help options are encountered. After showing the usage-message, the program will terminate. If you want to handle -h or --help options manually (as all other options), set help=false.

• version, by default nil, is an optional argument that specifies the version of your program. If supplied, then, if the parser encounters --version option, it will print the supplied version and terminate. version could be any printable object, but most likely a string, e.g. '2.1.0rc1'.

Note, when docopt is set to automatically handle -h, --help and --version options, you still need to mention them in the options description (doc) for your users to know about them.

The return value is just a hash with options, arguments and commands, with keys spelled exactly like in a help message (long versions of options are given priority). For example, if you invoke the top example as:

$ naval_fate.rb ship Guardian move 100 150 --speed=15

the return hash will be::

{
  "ship" => true,
  "new" => false,
  "<name>" => ["Guardian"],
  "move" => true,
  "<x>" => "100",
  "<y>" => "150",
  "--speed" => "15",
  "shoot" => false,
  "mine" => false,
  "set" => false,
  "remove" => false,
  "--moored" => false,
  "--drifting" => false,
  "--help" => false,
  "--version" => false
}

This port of docopt follows the docopt help message format. You can find more details at official docopt git repo

The examples directory contains several examples which cover most aspects of the docopt functionality.