a command line option parser that will make you smile

docopt – a command line option parser that will make you smile

docopt is a language for description of command-line interfaces. This is docopt implementation in CoffeeScript, that could be used for server-side CoffeeScript and JavaScript programs.

Isn't it awesome how modern command-line arguments parsers generate help message based on your code?!

Hell no! You know what's awesome? When the option parser is generated based on the help message that you write yourself! This way you don't need to write this stupid repeatable parser-code, and instead can write a beautiful help message (the way you want it!), which adds readability to your code.

Now you can write an awesome, readable, clean, DRY code like this:

doc = """
Usage: tcp <host> <port> [--timeout=<seconds>] serial <port> [--baud=9600] [--timeout=<seconds>] -h | --help | --version
{docopt} = require '../docopt'
console.log docopt(docversion: '0.1.1rc')

Hell yeah! The option parser is generated based on doc string above, that you pass to the docopt function.

docopt takes 1 required argument, and 3 optional keyword arguments:

  • doc (required) should be a string with the help message, written according to rules of the docopt language. Here's a quick example:

    Usage: your_program [options]
      -h --help     Show this.
      -v --verbose  Print more text.
      --quiet       Print less text.
      -o FILE       Specify output file [default: ./test.txt].
  • argv is an optional argument vector. It defaults to the arguments passed to your program (process.argv[2..]). You can also supply it with an array of strings, as with process.argv. For example: ['--verbose', '-o', 'hai.txt'].

  • help (default:true) specifies whether the parser should automatically print the help 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 (the same as other options), set help=false.

  • version (default:null) 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'.

  • options_first, by default false. If set to true will disallow mixing options and positional argument. I.e. after first positional argument, all arguments will be interpreted as positional even if the look like options. This can be used for strict compatibility with POSIX, or if you want to dispatch your arguments to other programs.

  • exit, by default true. If set to false will cause docopt to throw exceptions instead of printing the error to console and terminating the application. This flag is mainly for testing purposes.

Note: Although docopt automatically handles -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 an Object with properties (giving long options precedence), like this:

{'--timeout': '10',
 '--baud': '4800',
 '--version': false,
 '--help': false,
 '-h': false,
 serial: true,
 tcp: false,
 '<host>': false,
 '<port>': '/dev/ttyr01'}