Usage

Let’s begin by looking at two examples, one where we mimic the POSIX command-line interface to the rm command. Looking at the entry in the standard, rm takes the following options:

-f

Do not prompt for confirmation.

-i

Prompt for confirmation.

-R

Remove file hierarchies.

-r

Equivalent to -r.

It also takes the following arguments:

FILE

A pathname or directory entry to be removed.

And actually allows one or more of these FILE arguments to be given.

We also note that the rm command is described as a command to “remove directory entries”.

Let’s turn this specification into one using Ame’s API. We begin by adding a flag for each of the options listed above:

class Rm < Ame::Root
  flag 'f', '', false, 'Do not prompt for confirmation'
  flag 'i', '', nil, 'Prompt for confirmation' do |options|
    options['f'] = false
  end
  flag 'R', '', false, 'Remove file hierarchies'
  flag 'r', '', nil, 'Equivalent to -R' do |options|
    options['r'] = true
  end

A flag is a boolean option that doesn’t take an argument. Each flag gets a short and long name, where an empty name means that there’s no corresponding short or long name for the flag, a default value (true, false, or nil), and a description of what the flag does. Each flag can also optionally take a block that can do further processing. In this case we use this block to modify the Hash that maps option names to their values passed to the block to set other flags’ values than the ones that the block is associated with. As these flags (‘i’ and ‘r’) aren’t themselves of interest, their default values have been set to nil, which means that they won’t be included in the Hash that maps option names to their values when passed to the method.

There are quite a few other kinds of options besides flags that can be defined using Ame, but flags are all that are required for this example. We’ll get to the other kinds in later examples.

Next we add a “splus” argument.

  splus 'FILE', String, 'File to remove'

A splus argument is like a Ruby “splat”, that is, an Array argument at the end of the argument list to a method preceded by a star, except that a splus requires at least one argument. A splus argument gets a name for the argument (FILE), the type of argument it represents (String), and a description.

Then we add a description of the command (method) itself:

  description 'Remove directory entries'

Descriptions will be used in help output to assist the user in using the command.

Finally, we add the Ruby method that’ll implement the command (all preceding code included here for completeness):

class Rm < Ame::Root
  version '1.0.0'

  flag 'f', '', false, 'Do not prompt for confirmation'
  flag 'i', '', nil, 'Prompt for confirmation' do |options|
    options['f'] = false
  end
  flag 'R', '', false, 'Remove file hierarchies'
  flag 'r', '', nil, 'Equivalent to -R' do |options|
    options['r'] = true
  end
  splus 'FILE', String, 'File to remove'
  description 'Remove directory entries'
  def rm(files, options = {})
    require 'fileutils'
    FileUtils.send options['R'] ? :rm_r : :rm,
      [first] + rest, :force => options['f']
  end
end

Actually, another bit of code was also added, namely

  version '1.0.0'

This sets the version String of the command. This information is used when the command is invoked with the “--version” flag. This flag is automatically added, so you don’t need to add it yourself. Another flag, “--help”, is also added automatically. When given, this flag’ll make Ame output usage information of the command.

To actually run the command, all you need to do is invoke

Rm.process

This’ll invoke the command using the command-line arguments stored in ARGV, but you can also specify other ones if you want to:

Rm.process 'rm', %w[-r /tmp/*]

The first argument to #process is the name of the method to invoke, which defaults to File.basename($0), and the second argument is an Array of Strings that should be processed as command-line arguments passed to the command.

If you’d store the complete Rm class defined above in a file called rm and add #! /usr/bin/ruby -w at the beginning and Rm.process at the end, you’d have a fully functional rm command (after making it executable). Let’s see it in action:

% rm --help
Usage: rm [OPTIONS]... FILE...
  Remove directory entries

Arguments:
  FILE...  File to remove

Options:
  -R             Remove file hierarchies
  -f             Do not prompt for confirmation
      --help     Display help for this method
  -i             Prompt for confirmation
  -r             Equivalent to -R
      --version  Display version information
% rm --version
rm 1.0.0

Some commands are more complex than rm. For example, git has a rather complex command-line interface. We won’t mimic it all here, but let’s introduce the rest of the Ame API using a fake git clone as an example.

Git uses sub-commands to achieve most things. Implementing sub-commands with Ame is done using a “dispatch”. We’ll discuss dispatches in more detail later, but suffice it to say that a dispatch delegates processing to a child class that’ll handle the sub-command in question. We begin by defining our main git command using a class called Git under the Git::CLI namespace:

module Git end
class Git::CLI < Ame::Root
  version '1.0.0'
  class Git < Ame::Class
    description 'The stupid content tracker'
    def initialize; end

We’re setting things up to use the Git class as a dispatch in the Git::CLI class. The description on the initialize method will be used as a description of the git dispatch command itself.

Next, let’s add the format-patch sub-command:

description 'Prepare patches for e-mail submission'
flag   ?n, 'numbered', false, 'Name output in [PATCH n/m] format'
flag   ?N, 'no-numbered', nil,
  'Name output in [PATCH] format' do |options|
  options['numbered'] = false
end
toggle ?s, 'signoff', false,
  'Add Signed-off-by: line to the commit message'
switch '', 'thread', 'STYLE', nil,
  Ame::Types::Enumeration[:shallow, :deep],
'Controls addition of In-Reply-To and References headers'
flag   '', 'no-thread', nil,
  'Disables addition of In-Reply-To and Reference headers' do |options, _|
   options.delete 'thread'
end
option '', 'start-number', 'N', 1,
  'Start numbering the patches at N instead of 1'
multioption '', 'to', 'ADDRESS', String,
  'Add a To: header to the email headers'
optional 'SINCE', 'N/A', 'Generate patches for commits after SINCE'
def format_patch(since = '', options = {})
  p since, options
end

We’re using quite a few new Ame commands here. Let’s look at each in turn:

toggle ?s, 'signoff', false,
  'Add Signed-off-by: line to the commit message'

A “toggle” is a flag that also has an inverse. Beyond the flags ‘s’ and “signoff”, the toggle also defines “no-signoff”, which will set “signoff” to false. This is useful if you want to support configuration files that set “signoff”’s default to true, but still allow it to be overridden on the command line.

When using the short form of a toggle (and flag and switch), multiple ones may be juxtaposed after the initial one. For example, “-sn” is equivalent to “-s -n” to “git format-patch›”.

switch '', 'thread', 'STYLE', nil,
  Ame::Types::Enumeration[:shallow, :deep],
  'Controls addition of In-Reply-To and References headers'

A “switch” is an option that takes an optional argument. This allows you to have separate defaults for when the switch isn’t present on the command line and for when it’s given without an argument. The third argument to a switch is the name of the argument. We’re also introducing a new concept here in Ame::Types::Enumeration. An enumeration allows you to limit the allowed input to a set of Symbols. An enumeration also has a default value in the first item to its constructor (which is aliased as .[]). In this case, the “thread” switch defaults to nil, but, when given, will default to :shallow if no argument is given. If an argument is given it must be either “shallow” or “deep”. A switch isn’t required to take an enumeration as its argument default and can take any kind of default value for its argument that Ame knows how to handle. We’ll look at this in more detail later, but know that the type of the default value will be used to inform Ame how to parse a command-line argument into a Ruby value.

An argument to a switch must be given, in this case, as “--thread=deep” on the command line.

option '', 'start-number', 'N', 1,
  'Start numbering the patches at N instead of 1'

An “option” is an option that takes an argument. The argument must always be present and may be given, in this case, as “--start-number=2” or “--start-number 2” on the command line. For a short-form option, anything that follows the option is seen as an argument, so assuming that “start-number” also had a short name of ‘S’, “-S2” would be equivalent to “-S 2”, which would be equivalent to “--start-number 2”. Note that “-snS2” would still work as expected.

multioption '', 'to', 'ADDRESS', String,
  'Add a To: header to the email headers'

A “multioption” is an option that takes an argument and may be repeated any number of times. Each argument will be added to an Array stored in the Hash that maps option names to their values. Instead of taking a default argument, it takes a type for the argument (String, in this case). Again, types are used to inform Ame how to parse command-line arguments into Ruby values.

optional 'SINCE', 'N/A', 'Generate patches for commits after SINCE'

An “optional” argument is an argument that isn’t required. If it’s not present on the command line it’ll get its default value (the String 'N/A', in this case).

We’ve now covered all kinds of options and one new kind of argument. There are three more types of argument (one that we’ve already seen and two new) that we’ll look into now: “argument”, “splat”, and “splus”.

description 'Annotate file lines with commit information'
argument 'FILE', String, 'File to annotate'
def annotate(file)
  p file
end

An “argument” is an argument that’s required. If it’s not present on the command line, an error will be raised (and by default reported to the terminal). As it’s required, it doesn’t take a default, but rather a type.

description 'Add file contents to the index'
splat 'PATHSPEC', String, 'Files to add content from'
def add(paths)
  p paths
end

A “splat” is an argument that’s not required, but may be given any number of times. The type of a splat is the type of one argument and the type of a splat as a whole is an Array of values of that type.

description 'Display gitattributes information'
splus 'PATHNAME', String, 'Files to list attributes of'
def check_attr(paths)
  p paths
end

A “splus” is an argument that’s required, but may also be given any number of times. The type of a splus is the type of one argument and the type of a splus as a whole is an Array of values of that type.

Now that we’ve seen all kinds of options and arguments, let’s look on an additional tool at our disposal, the dispatch.

class Remote < Ame::Class
  description 'Manage set of remote repositories'
  def initialize; end

  description 'Shows a list of existing remotes'
  flag 'v', 'verbose', false, 'Show remote URL after name'
  def list(options = {})
    p options
  end

  description 'Adds a remote named NAME for the repository at URL'
  argument 'name', String, 'Name of the remote to add'
  argument 'url', String, 'URL to the repository of the remote to add'
  def add(name, url)
    p name, url
  end
end

Here we’re defining a child class to Git::CLI::Git called “Remote” that doesn’t introduce anything new. Then we set up the dispatch:

dispatch Remote, :default => 'list'

This adds a method called “remote” to Git::CLI::Git that will dispatch processing of the command line to an instance of the Remote class when “git remote” is seen on the command line. The “remote” method expects an argument that’ll be used to decide what sub-command to execute. Here we’ve specified that in the absence of such an argument, the “list” method should be invoked.

We add the same kind of dispatch to Git under Git::CLI:

dispatch Git

and then we’re done. Here’s all the previous code in its entirety:

module Git end
class Git::CLI < Ame::Root
  version '1.0.0'
  class Git < Ame::Class
    description 'The stupid content tracker'
    def initialize; end

    description 'Prepare patches for e-mail submission'
    flag   ?n, 'numbered', false, 'Name output in [PATCH n/m] format'
    flag   ?N, 'no-numbered', nil,
      'Name output in [PATCH] format' do |options|
      options['numbered'] = false
    end
    toggle ?s, 'signoff', false,
      'Add Signed-off-by: line to the commit message'
    switch '', 'thread', 'STYLE', nil,
      Ame::Types::Enumeration[:shallow, :deep],
      'Controls addition of In-Reply-To and References headers'
    flag   '', 'no-thread', nil,
      'Disables addition of In-Reply-To and Reference headers' do |options, _|
       options.delete 'thread'
    end
    option '', 'start-number', 'N', 1,
      'Start numbering the patches at N instead of 1'
    multioption '', 'to', 'ADDRESS', String,
      'Add a To: header to the email headers'
    optional 'SINCE', 'N/A', 'Generate patches for commits after SINCE'
    def format_patch(since = '', options = {})
      p since, options
    end

    description 'Annotate file lines with commit information'
    argument 'FILE', String, 'File to annotate'
    def annotate(file)
      p file
    end

    description 'Add file contents to the index'
    splat 'PATHSPEC', String, 'Files to add content from'
    def add(paths)
      p paths
    end

    description 'Display gitattributes information'
    splus 'PATHNAME', String, 'Files to list attributes of'
    def check_attr(paths)
      p paths
    end

    class Remote < Ame::Class
      description 'Manage set of remote repositories'
      def initialize; end

      description 'Shows a list of existing remotes'
      flag 'v', 'verbose', false, 'Show remote URL after name'
      def list(options = {})
        p options
      end

      description 'Adds a remote named NAME for the repository at URL'
      argument 'name', String, 'Name of the remote to add'
      argument 'url', String, 'URL to the repository of the remote to add'
      def add(name, url)
        p name, url
      end
    end
    dispatch Remote, :default => 'list'
  end
  dispatch Git
end

If we put this code in a file called “git” and add #! /usr/bin/ruby -w at the beginning and Git::CLI.process at the end, you’ll have a very incomplete git command-line interface on your hands. Let’s look at what some of its --help output looks like:

% git --help
Usage: git [OPTIONS]... METHOD [ARGUMENTS]...
The stupid content tracker

Arguments:
  METHOD          Method to run
  [ARGUMENTS]...  Arguments to pass to METHOD

Options:
  --help     Display help for this method
  --version  Display version information

Methods:
  add           Add file contents to the index
  annotate      Annotate file lines with commit information
  check-attr    Display gitattributes information
  format-patch  Prepare patches for e-mail submission
  remote        Manage set of remote repositories
% git format-patch --help
Usage: git format-patch [OPTIONS]... [SINCE]
Prepare patches for e-mail submission

Arguments:
  [SINCE=N/A]  Generate patches for commits after SINCE

Options:
  -N, --no-numbered     Name output in [PATCH] format
      --help            Display help for this method
  -n, --numbered        Name output in [PATCH n/m] format
      --no-thread       Disables addition of In-Reply-To and Reference headers
  -s, --signoff         Add Signed-off-by: line to the commit message
      --start-number=N  Start numbering the patches at N instead of 1
      --thread[=STYLE]  Controls addition of In-Reply-To and References headers
      --to=ADDRESS*     Add a To: header to the email headers
% git remote --help
Usage: git remote [OPTIONS]... [METHOD] [ARGUMENTS]...
Manage set of remote repositories

Arguments:
  [METHOD=list]   Method to run
  [ARGUMENTS]...  Arguments to pass to METHOD

Options:
  --help  Display help for this method

Methods:
  add   Adds a remote named NAME for the repository at URL
  list  Shows a list of existing remotes

API

The previous section gave an introduction to the whole user API in an informal and introductory way. For an indepth reference to the user API, see the user API documentation.

If you want to extend the API or use it in some way other than as a command-line-interface writer, see the developer API documentation.

Financing

Currently, most of my time is spent at my day job and in my rather busy private life. Please motivate me to spend time on this piece of software by donating some of your money to this project. Yeah, I realize that requesting money to develop software is a bit, well, capitalistic of me. But please realize that I live in a capitalistic society and I need money to have other people give me the things that I need to continue living under the rules of said society. So, if you feel that this piece of software has helped you out enough to warrant a reward, please PayPal a donation to now@disu.se. Thanks! Your support won’t go unnoticed!

Reporting Bugs

Please report any bugs that you encounter to the issue tracker.

Authors

Nikolai Weibull wrote the code, the tests, the documentation, and this README.

Licensing

Ame is free software: you may redistribute it and/or modify it under the terms of the GNU Lesser General Public License, version 3 or later, as published by the Free Software Foundation.