how to use getoptlog in ruby

Question

opts = GetoptLong.new(
  [ '--help', '-h', GetoptLong::NO_ARGUMENT ],
  [ '--repeat', '-n', GetoptLong::REQUIRED_ARGUMENT ],
  [ '--name', GetoptLong::OPTIONAL_ARGUMENT ]
)

I have this kind of declaration for optlong. Can anyone tell me if opts works as an array or as a hash and also what are the values in opts. One more thing

opts.each do |opt,args|

what are the valuse in opt and args respeectively?

Please help me out

Answer 1

opt,arg:

opt is the actual option passed, which in your case would be help/repeat/name. arg would be the value of the argument.

For instance, if you give

--name amit then you would get arg value = amit

Also, it is most likely that options is a hash.

NO_ARGUMENT: It takes just '-h'/'--help', but does not take any argument.

REQUIRED_ARGUMENT: It needs an argument to be specified. For example just ' --repeat' will be rejected.

OPTIONAL_ARGUMENT: You can either supply an argument to the option, or not. e.g., think of ls. You can say 'ls' and it will list the contents of directory, or you could say 'ls .'/'ls '...

EDIT: Please look at this for a brief explanation of Getopt (both variations). http://ruby.about.com/od/advancedruby/a/commandoptions.htm

Answer 2

opt holds the 'long' version of the option. arg holds the corresponding argument. I usually write something similar to the code below when I use getoptlong.

opts.each do |opt, arg|
  case opt
  when '--help'
    RDoc::usage
    exit(0)
  when '--repeat'
    puts "--repeat argument was #{arg}"
  end
end

So if you enter foo.rb -n 8, arg will hold 8 when the '--repeat' branch is executed. Hope this helps