Trollop

Informs the user that their usage of 'arg' was wrong, as detailed by 'msg', and dies. Example:

options do
  opt :volume, :default => 0.0
end

die :volume, "too loud" if opts[:volume] > 10.0
die :volume, "too soft" if opts[:volume] < 0.1

In the one-argument case, simply print that message, a notice about -h, and die. Example:

options do
  opt :whatever # ...
end

Trollop::die "need at least one filename" if ARGV.empty?

# File lib/trollop.rb, line 772
def die arg, msg=nil
  if @last_parser
    @last_parser.die arg, msg
  else
    raise ArgumentError, "Trollop::die can only be called after Trollop::options"
  end
end

The easy, syntactic-sugary entry method into Trollop. Creates a Parser, passes the block to it, then parses args with it, handling any errors or requests for help or version information appropriately (and then exiting). Modifies args in place. Returns a hash of option values.

The block passed in should contain zero or more calls to opt (Parser#opt), zero or more calls to text (Parser#text), and probably a call to version (Parser#version).

The returned block contains a value for every option specified with opt. The value will be the value given on the commandline, or the default value if the option was not specified on the commandline. For every option specified on the commandline, a key "<option name>_given" will also be set in the hash.

Example:

require 'trollop'
opts = Trollop::options do
  opt :monkey, "Use monkey mode"                    # a flag --monkey, defaulting to false
  opt :name, "Monkey name", :type => :string        # a string --name <s>, defaulting to nil
  opt :num_limbs, "Number of limbs", :default => 4  # an integer --num-limbs <i>, defaulting to 4
end

## if called with no arguments
p opts # => {:monkey=>false, :name=>nil, :num_limbs=>4, :help=>false}

## if called with --monkey
p opts # => {:monkey=>true, :name=>nil, :num_limbs=>4, :help=>false, :monkey_given=>true}

See more examples at trollop.rubyforge.org.

# File lib/trollop.rb, line 708
def options args=ARGV, *a, &b
  @last_parser = Parser.new(*a, &b)
  with_standard_exception_handling(@last_parser) { @last_parser.parse args }
end

If Trollop::options doesn't do quite what you want, you can create a Parser object and call Parser#parse on it. That method will throw CommandlineError, HelpNeeded and VersionNeeded exceptions when necessary; if you want to have these handled for you in the standard manner (e.g. show the help and then exit upon an HelpNeeded exception), call your code from within a block passed to this method.

Note that this method will call System#exit after handling an exception!

Usage example:

require 'trollop'
p = Trollop::Parser.new do
  opt :monkey, "Use monkey mode"                     # a flag --monkey, defaulting to false
  opt :goat, "Use goat mode", :default => true       # a flag --goat, defaulting to true
end

opts = Trollop::with_standard_exception_handling p do
  o = p.parse ARGV
  raise Trollop::HelpNeeded if ARGV.empty? # show help screen
  o
end

Requires passing in the parser object.

# File lib/trollop.rb, line 738
def with_standard_exception_handling parser
  begin
    yield
  rescue CommandlineError => e
    $stderr.puts "Error: #{e.message}."
    $stderr.puts "Try --help for help."
    exit(-1)
  rescue HelpNeeded
    parser.educate
    exit
  rescue VersionNeeded
    puts parser.version
    exit
  end
end