docopt.rb – command line option parser, that will make you smile

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

New in version 0.5.0:

Repeatable flags and commands are counted if repeated (a-la ssh -vvv).
Repeatable options with arguments are accumulated into list.

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"
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
  require "pp"
  pp Docopt::docopt(doc)
rescue Docopt::Exit => e
  puts e.message
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.

Installation

Docopt is available via rubygems:

gem install docopt

Alternatively, you can just drop lib/docopt.rb file into your project--it is
self-contained. Get source on github.

docopt has been confirmed to work with 1.8.7p370 and 1.9.3p194. If you have
noticed it working (or not working) with an earlier version, please raise an
issue and we will investigate support.

API

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 dictionary 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 dictionary 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}

Help message format

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

Examples

We have an extensive list of
examples
which cover every aspect of functionality of docopt. Try them out,
read the source if in doubt.

Data validation

docopt does one thing and does it well: it implements your command-line
interface. However it does not validate the input data. We are looking
for ruby validation libraries to make your option parsing experiene
even more awesome!
If you've got any suggestions or think your awesome schema validation gem
fits well with docopt.rb, open an issue on github and enjoy the eternal glory!

Contribution

We would love to hear what you think about docopt.rb.
Contribute, make pull requrests, report bugs, suggest ideas and discuss
docopt.rb on
issues page.

If you want to discuss the original docopt reference,
point to it's home or
drop a line directly to vladimir@keleshev.com!

Porting docopt to other languages

Docopt is an interlinguistic (?) effort,
and this is the ruby port of docopt.
We coordinate our efforts with docopt community and try our best to
keep in sync with the python reference.

Docopt community loves to hear what you think about docopt, docopt.rb
and other sister projects on docopt's
issues page.