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Parse command line arguments from nothing more than a usage message

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Number of watchers on Github 432
Number of open issues 5
Average time to close an issue about 1 month
Main language Ruby
Average time to merge a PR 3 days
Open pull requests 3+
Closed pull requests 4+
Last commit over 1 year ago
Repo Created over 7 years ago
Repo Last Updated over 1 year ago
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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.

  #{__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

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


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

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.


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.


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::


Help message format

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


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!


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!

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.

docopt.rb open issues Ask a question     (View All Issues)
  • about 3 years Flag for multiple args nests array inside array
  • about 4 years test does not include example file
  • over 4 years docopt.rb neglects to set arguments to defaults when absent
  • over 4 years Warning: shadowing outer local variable
  • almost 5 years Optional argument not handling string hashes properly
  • about 5 years Indicate status in Exit exception
  • over 5 years Update to 0.6
  • about 7 years Bad error string when no argument specified for required short option
docopt.rb open pull requests (View All Pulls)
  • Convert params hash to symbols prior to merging.
  • Parity with 0.6.2
  • Add argv to readme
docopt.rb list of languages used
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