= Welcome to Choice Choice is a small library for defining and parsing command line options. It works awesomely with Highline[http://highline.rubyforge.org/] or other command line interface libraries. Choice was written by Chris Wanstrath as an exercise in test driving development of a DSL. This project is still an infant: bugs are expected and tattling on them is appreciated. Installing is easy, with RubyGems. Give it a shot: $ gem install choice If you are lost, you can find Choice at http://choice.rubyforge.org or http://rubyforge.org/projects/choice/. E-mail inquiries can be directed to mailto:chris[at]ozmm[dot]org. Of course, Choice is licensed under the MIT License, which you can find included in the LICENSE file or by surfing your World Wide Web browser of choice towards http://www.opensource.org/licenses/mit-license.php. == Using Choice An +examples+ directory is included with Choice, in which some contrived Ruby programs utilizing the library have been placed. Here's a snippet: === ftpd.rb require 'choice' PROGRAM_VERSION = 4 Choice.options do header '' header 'Specific options:' option :host do short '-h' long '--host=HOST' desc 'The hostname or ip of the host to bind to (default 127.0.0.1)' default '127.0.0.1' end option :port do short '-p' long '--port=PORT' desc 'The port to listen on (default 21)' cast Integer default 21 end separator '' separator 'Common options: ' option :help do long '--help' desc 'Show this message' end option :version do short '-v' long '--version' desc 'Show version' action do puts "ftpd.rb FTP server v#{PROGRAM_VERSION}" exit end end end puts 'port: ' + Choice[:port] Notice the last line. For free, you will be given a <tt>Choice.choices</tt> hash which contain, at runtime, the options found and their values. <tt>Choice[:key]</tt> is a shortcut for <tt>Choice.choices[:key]</tt>. Because we gave option <tt>:port</tt> a default of 21, <tt>Choice[:port]</tt> should be 21 if we run ftpd.rb with no options. Let's see. $ ruby ftpd.rb port: 21 Cool. On our system, port 21 is reserved. Let's use another port. $ ruby ftpd.rb -p 2100 port: 2100 Alright. And, of course, there is the hard way of doing things. $ ruby ftpd.rb --port=2100 port: 2100 That <tt>:version</tt> option looks pretty interesting, huh? I wonder what it does... $ ruby ftpd.rb -v ftpd.rb FTP server v4 That's not all, though. We also get a <tt>--help</tt> option for free. $ ruby ftpd.rb --help Usage: ftpd.rb [-hpv] Specific options: -h, --host=HOST The hostname or ip of the host to bind to (default 127.0.0.1) -p, --port=PORT The port to listen on (default 21) Common options: --help Show this message -v, --version Show version == The Choice.choices hash For better or worse, the <tt>Choice.choices</tt> hash is a bit lazy. It does not care how you access it. Using the above example, assume we have a <tt>:port</tt> option and we replace the last line of our program with the following three lines: puts 'port: ' + Choice.choices[:port] puts 'port: ' + Choice.choices['port'] puts 'port: ' + Choice.choices.port Now, run it. $ ftpd.rb -p 2100 port: 2100 port: 2100 port: 2100 Lazy, huh? Keep in mind that your option's key in the <tt>Choice.choices</tt> hash is defined by the first parameter passed to option statement. This is perfectly legit, albeit somewhat confusing: option :name do short '-h' long '--handle=NAME' desc "Your handle." end You can access this option by using <tt>Choice.choices[:name]</tt>, not <tt>:handle</tt>. == Option options Obviously, Choice revolves around the <tt>option</tt> statement, which receives a block. Here are all the, er, options +option+ accepts. None of them are required but +short+ or +long+ must be present for Choice to know what to do. Options must be defined in the context of a <tt>Choice.options</tt> block, as seen above. This context is assumed for the following explanations. For the quick learners, here's the list: * short * long * default * desc * cast * valid (takes array) * validate (takes regex) * filter (takes a block) * action (ditto) You can define these within your option in any order which pleases you. === short Defines the short switch for an option. Expected to be a dash and a single character. short '-s' === long Defines the long switch for an option. Expected to be a double dash followed by a string, an equal sign (or a space), and another string. There are two variants: longs where a parameter is required and longs where a parameter is optional, in which case the value will be +true+ if the option is present. *Optional*: long '--debug=[LEVEL]' Assuming our program defines Choices and ends with this line: puts 'debug: ' + Choice.choices[:debug] we can do this: $ ruby ftpd.rb --debug debug: true $ ruby ftpd.rb --debug=1 debug: 1 $ ruby ftpd.rb --debug 1 debug: 1 *Required*: long '--debug=LEVEL' Assuming the same as above: $ ruby ftpd.rb --debug 1 debug: 1 $ ruby ftpd.rb --debug <help screen printed> === long as array Often you may wish to allow users the ability to pass in multiple arguments and have them all combined into an array. You can accomplish this by defining a +long+ and setting the caps-argument to *ARG. Like this: long '--suit *SUITS' <tt>Choice.choices.suits</tt> will now return an array. Here's an example of usage: $ ruby --suit hearts clubs suit: ['hearts', 'clubs'] Check out <tt>examples/gamble.rb</tt> for more information on this cool feature. === default You can define a default value for your option, if you'd like. If the option is not present in the argument list, the default will be returned when trying to access that element of the <tt>Choice.choices</tt> hash. As with the above, assume our program prints <tt>Choice.choices[:debug]</tt>: default 'info' If we don't pass in <tt>--debug</tt>, the <tt>:debug</tt> element of our hash will be 'info.' $ ftpd.rb debug: info $ ftpd.rb --debug warn debug: warn === desc The description of this option. Fairly straightforward, with one little trick: multiple +desc+ statements in a single option will be considered new desc lines. The desc lines will be printed in the order they are defined. Like this: desc "Your hostname." desc "(default 'localhost')" A snippet from your <tt>--help</tt> might then look like this: -h, --host=HOST Your hostname. (default 127.0.0.1) === cast By default, all members of the <tt>Choice.choices</tt> hash are strings. If you want something different, like an Integer for a port number, you can use the +cast+ statement. cast Integer Currently support +cast+ options: * Integer * String * Float * Symbol We'll probably add Date, Time, and DateTime in the future, if people want them. === valid Giving +valid+ an array creates a whitelist of acceptable arguments. valid %w[clubs hearts spades diamonds] If our option is passed anything other than one of the four card suits, the help screen will be printed. It might be a good idea to include acceptable arguments in your option's "desc" value. $ ruby gamble.rb -s clubs suit: clubs $ ruby gamble.rb -s joker <help screen printed> === validate The +validate+ statement accepts a regular expression which it will test against the value passed. If the test fails, the <tt>--help</tt> screen will be printed. I love ports, so let's stick with that example: validate /^\d+$/ Of course, 2100 matches this: $ ruby ftpd.rb -p 2100 port: 2100 I like dogs. I wish dogs could be ports. Alas, Choice knows better (once I've told it so): $ ruby ftpd.rb -p labradoodle <help screen printed> === filter The +filter+ statement lets you play with a value before it goes into the <tt>Choice.choices</tt> hash. If you use +cast+, this will occur post-casting. In this program we're defining a :name option and saying we don't want any crazy characters in it, then printing that element of the <tt>Choice.choices</tt>+ hash: filter do |value| value = value.gsub(/[^\w]/, '') end Now: $ ruby ftpd.rb --name=c.hr.is name: chris You can probably think of better uses. === action A block passed to the +action+ statement will be run if that particular option is passed. See the <tt>--version</tt> example earlier. === required options You can specify an option as being required by passing :required => true to the option definition. Choice will then print the help screen if this option is not present. Please let your dear users know which options are required. For example: option :card, :required => true do short '-c' long '--card CARD' desc "The card you wish to gamble on. Required. Only one, please." end Then: $ ruby gamble.rb <help screen, -c or --card wasn't passed> == Other options These statements are purely aesthetic, used to help make your <tt>--help</tt> screen a little more digestible. Passing an empty string to any of these options will print a newline. === banner The banner is the first line printed when your program is called with <tt>--help</tt>. By default, it will be something like this, based on the options defined: Usage: ftpd.rb [-hpv] You can pass any string to the +banner+ statement to override what prints. This might be useful if you're into ascii art. banner "Usage: ftpd.rb" === header The header is what shows up after the banner but before your option definitions are printed. Each header call is a newline. Check out the example above. header "ftp is a harsh and unforgiving protocol." === separator As in the example above, you can put separators between options to help display the logical groupings of your options. Or whatever. separator "----" To get a blank line, rock an empty string: separator '' === footer The footer is displayed after all your options are displayed. Nothing new here, works like the other options above. footer "That's all there is to it!" == Shorthand Now that you've gone through all the hard stuff, here's the easy stuff: Choice options can be defined with a simple hash if you'd like. Here's an example, from the tests: Choice.options do header "Tell me about yourself?" header "" options :band => { :short => "-b", :long => "--band=BAND", :cast => String, :desc => "Your favorite band.", :validate => /\w+/ }, :animal => { :short => "-a", :long => "--animal=ANIMAL", :cast => String, :desc => "Your favorite animal." } footer "" footer "--help This message" end How's that tickle you? Real nice. == It looks like poetry That's it. Not much, I know. Maybe this will make handling your command line options a bit easier. You can always use the option parser in the standard Ruby library, but DSLs are just so cool. As one of my non-programmer friends said of a Ruby DSL: "It looks like poetry." == It's totally broken Okay, I knew this would happen. Do me a favor, if you have time: run +rake+ from the Choice directory and send me the output (mailto:chris[at]ozmm[dot]org). This'll run the unit tests. Also, if you would, send me a bit of information on your platform. Choice was tested on OS X and RHEL with a 2.4 kernel but who knows. Thanks a lot. == Thanks to For bug reports, patches, and ideas I'd be honored to thank the following: - Justin Bailey - Alexis Li