The easiest way to add command line control to your Ruby app.
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The easiest way to add command line control to your Ruby app.

Stop wasting time writing WET (Write Everything Twice) command line interpreters, or repeatedly writing code for existing ones like optparser, then writing help/usage methods that you constantly must update as your code changes. Now you can add a single line above an existing method and that method will be available from the command line.

Best of all the help/usage instructions are automatically generated using the method itself! When you change your methods the help instructions change automajically! There's no extra effort needed on your part.

The whole process can take as little as four lines of code:

  • Add a require 'commandable' line somewhere (I'd put it in my bin).
  • Then an extend Commandable inside your class.
  • Put a command "I do something!" line above your method.
  • And finally make a call to Commandable.execute(ARGV) in your bin file.

Now any method you want to make accessible from the command line requires just a single line of code and it's right where your method is so it's easy to find when you do want to change some functionality.

Don't think of Commandable as a way to add command line switches, think of it as a way to allow your app to be driven directly from the command line in a natural language kind of way.

You can now "use your words" to let people interact with your apps in a natural way. No more confusing switches that mean one thing in one program and something completely different in another. Can you believe some apps actually use -v for something other than "version" and -h for something other than "help?" Madness I say! Madness!

Latest version

2013-03-04 - Version: 0.3.2

Verified works with Ruby 2.0

Principle of Least Surprise

I've tried to follow the principle of least surprise so Commandable should just work like you would expect it to. As long as you expect it to work the same way as I do.


  • Ruby 1.9.3 or greater (Ruby 2.0 supported)
  • OS X or any Posix OS (It works, mostly, on Windows but it won't pass the tests because of some Unix commands I use in the tests but no in the code base)


From the command line:

$ [sudo] gem install commandable

Usage Instructions

After installing the Commandable gem require it somewhere that gets loaded before your class does:

require 'commandable'

Extend your class with the Commandable module:

require 'commandable'

class Foo
  extend Commandable

Then put command and a description above the method you want to make accessible. The description is optional but can be helpful since it's used when automatically building your help/usage instructions.

require 'commandable'

class Foo
  extend Commandable
  command "Explain what the command does"
  def bar
    puts "Foo::bar"

The "command" command and its options

command ["description"], [:required], [:default], [:priority=>(0...n)], [:xor[=>:group_name]]

command (required)
This is the only thing that's required. It tells Commandable to add the method that follows to the list of methods available from the command line.

description [optional]
As you would imagine this is a short description of what the method does. You can have multiple lines by using a new line, \n, in the description and your description will be lined up properly. This prints in the help/usage instructions when a user calls your programing using the command "help" or if they try to issue a command that doesn't exist. Help instructions will also print if they try to use your app without any parameters (if there isn't a default method that doesn't require parameters.).

:required [optional]
You can mark a method as required and the user must specify this command and any required parameters every time they run your app. You can also have a method marked as both :default and :required which allows you to run a method with a required parameter but you don't have to type the method name.

:default [optional]
You can have one and only one default method. This method will be called if your app is called with just parameters or if the first command line parameter isn't a command. The user can still give more commands after the parameters for the default command too.

For instance say your default method is :foo that takes one parameter and you have another method called :bar that also takes one parameter. A user could do this:

yourapp "Some Parameter" bar "A parameter for bar"

Just be aware that if they give an option that has the same name as a function the app will think it's a command.

priority=>n [optional]
This optional setting allows you to assign priorities to your methods so if you need them to be executed in a specific order, regardless of how the user specifies them on the command line, you can use this. Then when you execute the command line or ask for a queue of commands they will be sorted for you by priority.

The higher the priority the sooner the method will be executed. If you do not specify a priority a method will have a priority of 0, the lowest priority.

Note that you can have a default method with a lower priority than a non-default method.

:xor[=>:whatever] [optional]
The :xor parameter allows you to configure a group of methods as mutually exclusive, i.e. if method1 and method2 are in the same :xor group the user of your application can only call one of them at a time.

You can use just the :xor symbol and the method will be put into the default XOR group, called :xor so :xor=>:xor, but if you need multiple XOR groups you can specify a group name by using a hash instead of just the :xor symbol.

The XOR group name will be printed in the front to the description text so it's probably a good idea to use :xor as the prefix.

Parameter lists

When building the help/usage instructions a list of parameters for each command is automatically created using the names you give the parameters in your method; make sure you use descriptive names.

Also keep in mind that all command line parameters are strings so you need to deal with that inside your methods if what you really want is a number.

If none of your methods have parameters then there won't be any reference to parameters in the help/usage instructions. The description text will be moved over to be closer to your commands.

A complete class

A complete class might look like this:

require 'commandable'

class Widget
  extend Commandable

  command "create a new widget", :default, :priority=>10
  def new(name)
    "You made a widget named: #{name}"

  command "destroy an existing widget", :xor
  def delete(name)
    "No disassemble #{name}! #{name} is alive!"
  command "spend lots of money to update a widget", :xor
  def upgrade(name)
    "You just gave #{name} a nice new coat of paint!"

  command "your security key must be entered for every command", :required
  def key(security)
    # blah, blah, blah


Class methods

You can also use it on class methods:

require "commandable"

class ClassMethods
  extend Commandable

  command 'does some stuff'
  def self.class_method(string_arg1)

  # The first class method will get the command
  command "another one"
  class << self
    def class_method2(integer_arg1)

If you want to do a block of class commands using class << self you need to put extend Commandable inside the block:

require "commandable"

class ClassMethodsNested
  class << self
    extend Commandable

    command "hello world"
    def class_foo(int_arg1, number_arg2)
      [int_arg1, number_arg2]

    command "look a function"
    def class_bar(int_arg1, string_arg2="Number 42")
      [int_arg1, string_arg2]

Note: Class methods are called directly on the class while instance methods have an instance created for all calls to that class. This means if you set an instance variable in one method it will be available to any other method calls to that same class; just as if you had created an instance of your class and called methods on it.

Automatic usage/help generation

One of the great features of Commandable is that it automatically creates usage instructions based on your methods and the descriptions you provide for them. It then adds a help command for you that will print out these usage instructions when called.

If your app has no :default method or it has a default command that requires parameters the help/usage instructions will be printed if a user just runs your app without any input.

A typical help output looks something like this:

 Commandable - The easiest way to add command line control to your app.
 Copyrighted free software - Copyright (c) 2011 Mike Bethany.
 Version: 0.2.0

 Usage: commandable <command> [parameters] [<command> [parameters]...]

  Command Parameters Description
   error            : Will raise a programmer error, not a user error
                      so you see what happens when you have bad code
examples [path]     : Copies the test classes to a folder so
                      you can see a bunch of small examples
  readme            : displays the readme file (default)
       v            : <xor> Application Version
 version            : <xor> Application Version
    help            : you're looking at it now 

Complete demonstration app and some example classes

Commandable uses Commandable for its own command line options so you can look at the lib/commandable/app_controller.rb class for an example.

If you would like to see a bunch of simple classes that demonstrate how to use Commandable run:

$ commandable examples [path]

Commandable Options

These are the basic options you'll want to be aware of. Specifically you really want to set Commandable#app_exe and Commandable#app_info so that the help/usage instructions are fully fleshed out.

default = ""
This is what a user would type to run your app; don't set it to "My App" set it to "myapp". When this is configured the help instructions will include a usage line with your executable's name.

default = ""
This is informational text that will print above the help/usage instructions.

default = false
If set to true help instructions will include the default values in the parameter list.
Important! This should only be set once, after you require 'commandable' but before any of your code files load. Changing the value after files are loaded will make no difference since parameters are only parsed when the source file loads.

Commandable.verbose_parameters = true
# Will print:
command arg1 [arg2="default value"]

Commandable.verbose_parameters = false
# Will print:
command arg1 [arg2]

###Screen Clearing Options

default = false
Set to true to enable clearing the screen when printing help/usage instructions.

_default = "\e[H\e[2J" The escape codes used to clear the screen.

Colorized Output Options

The help information can be colored using the standard ANSI escape commands found in the term-ansicolor gem. The term-ansicolor gem is installed as a dependency but just in case you have problems you can install it yourself by running:

$ [sudo] gem install term-ansicolor

Then you can do something like this:

require 'term/ansicolor'

c = Term::ANSIColor

Commandable.color_app_info           = c.intense_white  + c.bold
Commandable.color_app_exe            = c.intense_green  + c.bold
Commandable.color_command            = c.intense_yellow
Commandable.color_description        = c.intense_white
Commandable.color_parameter          = c.intense_cyan
Commandable.color_usage              = c.intense_black   + c.bold

Commandable.color_error_word         = c.intense_black   + c.bold
Commandable.color_error_name         = c.intense_red     + c.bold
Commandable.color_error_description  = c.intense_white   + c.bold

###Color options

default = false
Set to true to enable colorized help/usage instructions.

default = intense_white + bold
The color the app_info text will be in the help message

default = intense_green + bold
The color the app_exe will be in the usage line in the help message

default = intense_yellow
The color the word "command" and the commands themselves will be in the help message

default = intense_white
The color the word "command" and the commands themselves will be in the help message

default = intense_cyan
The color the word "parameter" and the parameters themselves will be in the help message

default = intense_black + bold
The color the word "Usage:" will be in the help message.

default = intense_white
The color the word "Error:" text will be in error messages

default = intense_cyan
The color the friendly name of the error will be in error messages

_default = intense_black_ + bold
The color the error description will be in error messages

The best way to see what all this means it just type commandable help and you'll see the help instructions in color.

Executing the Command Line

There are two ways of using Commandable to run your methods. You can use its built in execute method to automatically run whatever is entered on the command line or you can have Commandable build an array of procs that you can execute yourself. This allows you to have finer grain control over the execution of the commands as you can deal with the return values as you run each command.

The Easy way


After you've added a command method and a description above a method you can then get an array of command you should execute by sending the command line arguments (ARGV) to Commandable#execution_queue. That method will generate an array of procs to run based on the user's input. They're sorted by the order of priority you specified when creating the commands or if they all have the same priority they sort by how they were entered.

# execution_queue returns an array of hashes which 
# in turn  contains the method name keyed to :method
# and a proc keyed to, you guessed it, :proc
# It looks like this:
# [{:method => :method_name, :xor=>(:xor group or nil), :parameters=>[...], :priority=>0, :proc => #<proc:>}, ...]
# The array is automatically sorted by priority (higher numbers first, 10 > 0)

# First get the array of commands
command_queue = Commandable.execution_queue(ARGV) # #ARGV will be cloned so it won't change it

# Loop through the array calling the commands and dealing with the results
command_queue.each do |cmd|

  # If you need more data about the method you can
  # get the method properties from Commandable[]
  method_name = cmd[:method]
  description = Commandable[method_name][:description]
  puts description

  return_values = cmd[:proc].call

  case method_name
    when :some_method
      # do something with the return values
      # based on it being some_method
    when :some_other_method
      # do something with the return values
      # based on it being some_other_method
      # do something by default

The even easier way


The easiest way to use Commandable is to just let it do all the work. This works great if all you need to do is make your methods available from the command line. You can also design a controller class with Commandable in mind and run all you commands from there.

When you call the Commandable#execute method it will print out the return values for each method called automatically. This method is really meant to be the super easy way to do things. No muss, no fuss. Fire and forget. Shooting fish in a barrel... etc.

You just need to configure your bin file with the app settings and then run Commandable#execute:

[your Ruby app directory]/bin/your_app_name

#!/usr/bin/env ruby
$LOAD_PATH.unshift File.expand_path(File.dirname(__FILE__) + "/../lib")
require 'commandable'
Commandable.verbose_parameters = false
Commandable.color_output = true
Commandable.app_exe = "myapp"
Commandable.app_info =
  My App - It does stuff and things!
  Copyright (c) 2011 Acme Inc.

# Make sure you require your app after Commandable, or use
# a configuration file to load the settings then your app
require 'yourappname'

# If you don't want the output from your methods to be printed automatically
# for instance if your method already outputs some text, you can add :silent
# to the execute command like this:
# Commandable.execute(ARGV, :silent)

I actually prefer to create a separate file for my Commandable configuration and load it in my main app file in the lib directory.

In closing...

One really cool thing about this design is you can dynamically extend another app and add your own command line controls without having to crack open their code. The other app doesn't even have to use Commandable. You can just write your own methods that call the methods of the original program.

I should also say the code is really, really ugly right now. Thats the very next thing I will be working on for this project. This is the "rough draft" version that works perfectly well but is very ugly code-wise. I needed to use it right now so am putting it out as is.

If you have any questions about how the code works I've tried to give as much info in these docs as possible but I am also an OCD level commenter so you should be able to find fairly good explanations of what I'm doing in the code.

Most of all it should be simple to use so if you have any problems please drop me a line. Also if you make any changes please send me a pull request. I hate when people don't respond to them, even to deny them, so I'm pretty good about that sort of thing.

Version History

2013-04-04 - Version: 0.3.2

  • Works with Ruby 2.0

2012-02-07 - Version: 0.3.1

  • Fixed bug where an error was raised if a non-commandable method was before a commandable method (uninitialized class variable @@command_options)

2012-01-20 - Version: 0.3.0

  • All features are off by default to make Commandable more friendly across platforms.
  • Added ability to disable screen clearing and to set your own screen clear escape code. (Based on John Sumsion's idea)
  • Decoupled screen clearing from coloring; you can have neither, either, or both.
  • Fixed bug that disabled help output in silent mode. (fixed by John Sumsion)
  • Fixed bug that didn't label the default method if screen colors were off.
  • Removed monkey patch from FileUtils. It was more philosophical than necessary.
  • Changed terminal coloring gem back to official the term-ansicolor from my own fork now that my changes have been pulled into it.
  • Code clean up. While mostly not a real refactor I've separated out the code into functional groups (aka files).
  • Removed Widget gem example - it was making the examples too tightly coupled to HashModel.
  • Removed Cucumber features.

2011-09-27 - Version: 0.2.3

  • Removed annoying error message print out.

2011-08-31 - Version: 0.2.2

  • Added ability to do use Kernel.exit without Commandable trapping the error. (Andrew Vos)
  • Kernel.exit properly forwards exit status if given one. (Andrew Vos)

2011-04-04 - Version: 0.2.1

  • Added ability to use attr_accessor and att_writer as commands. You can only write to them of course but it's an easy way to set values.
  • Instance methods now retain state between different calls. In other words if you set an instance variable in one method it will be available to any other instance method calls for that class. It's as if you created an instance of your class and called the methods yourself. You can access the class instances using the hash Commandable.class_cache. It uses the class name, a string, as the key and the instance of the class as the value. {"ClassName"=>#ClassName:0x00000100b1f188}
  • You can now have the execute command work without outputting anything. Just add :silent (or anything other than nil or false) to the execution method. For instance Commandable.execute(ARGV,:silent).
  • Clarified error message for default methods that are also required. If you don't give anything it tells you you need to give a parameter but you don't specifically have to give the switch.

2011-03-23 - Version: 0.2.0

  • First public release. It's 0.2.0 because 0.1.0, going by the name of Cloptions, wasn't released.

Possible future upgrades/improvements

  • See if there's a elegant way to add nested argument trees without case blocks. e.g. a command that takes set of commands like foo remote set "ftp_svr" and foo remote delete "ftp_svr".
  • Add a way to use or discover version numbers. Might have to force standardization and not allow configuration since it should be DRY.
  • Add a generator to automatically add Commandable support to your app.
  • Try to figure out how to trap alias so you don't have to use an additional command.
  • Use comments below command as the description text so you don't have to repeat yourself when documenting your code.
  • Clean up RSpecs. I'm doing too many ugly tests instead of specifying behavior.
  • Allow sorting of commands alphabetically or by priority in the help output
  • Make the help/usage directions format available to programmers without having to hack the code.
  • More edge case testing.
  • Allow optional parameters values to be reloaded so changing things like verbose_parameters makes the command list change. (very low priority)
  • Accepting your suggestions...