From: Eric Mahurin <eric_mahurin@...>
Date: 2005-09-13T23:58:01+09:00
Subject: yet another simple command-line option parser

I just put in a good example for:

http://rcrchive.net/rcr/show/317

It is a simple option parser that has option defaults and
converts the options to the right type:

# these klass.from_s methods are the meat of the RCR
def Float.from_s(s);s.to_f;end
def Integer.from_s(s);s.to_i;end
def Symbol.from_s(s);s.to_sym;end
def String.from_s(s);s.to_s;end
def Regexp.from_s(s,*other);new(s,*other);end
require 'time.rb'
def Time.from_s(s,*other);Time.parse(s,*other);end

def argv_options(options)
    i = 0
    while arg = ARGV[i]
        if arg[0]==?-
            arg.slice!(0)
            ARGV.slice!(i)
            break if arg=="-" # -- terminates options
            opt = arg.to_sym
            default = options[opt]
            if default
                klass = default.class
                # would need a big case statement w/o RCR 317
                options[opt] = klass.from_s(ARGV.slice!(i))
            elsif default.nil?
                raise("unknown option -#{opt}")
            else # default==false
                options[opt] = true
            end
        else
            i += 1
        end
    end
    options
end

ARGV.replace(%w(
    -n 4
    -multiplier 3.14
    -q
    -title foobar
    -pattern fo+
    -time 5:55PM
    -method downcase
    a b c
))
# option => default (or false for a flag)
argv_options(
    :n => 1,
    :multiplier => 1.0,
    :q => false,
    :title => "hello world!",
    :pattern => /.*/,
    :time => Time.new,
    :method => :to_s
)


If you have an opinion about the usefulness of this RCR, go
vote and give a comment.  I didn't have an example before to
show it in action.


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