From: Robert Klemme <shortcutter@...>
Date: 2010-11-16T17:04:54+09:00
Subject: Re: Stupid optparse question

On Mon, Nov 15, 2010 at 11:17 PM, Chris Patti <cpatti@gmail.com> wrote:
> On Mon, Nov 15, 2010 at 4:45 PM, Robert Klemme
> <shortcutter@googlemail.com> wrote:
>> On 11/15/2010 10:27 PM, Chris Patti wrote:
>>>
>>> How can I make my code print the usage even if zero options are given?
>>>  I had *thought* opts.on_tail would do this, but it doesn't seem to be
>>> working.  The usage prints properly if I use -h though:
>>> ---
>>> require 'optparse'
>>>
>>> options = {}
>>
>> o = OptionParser.new do |opts|
>>
>>>   opts.banner = "Usage: #$0 [options] [terms]"
>>>
>>>   opts.on("-a", "--automatic", "Use current Git repo to determine
>>> current and next release branch and tag names") do |a|
>>>     options[:automatic] = a
>>>   end
>>>
>>>   opts.on("-n", "--next-branch [nextbranch]", "The branch you want
>>> this script to create.") do |n|
>>>     options[:nextbranch] = n
>>>   end
>>>
>>>   opts.on("-t", "--tag [tag]", "The tag you want the new branch
>>> created from.") do |t|
>>>     options[:tag] = t
>>>   end
>>>
>>>   opts.on_tail("-h", "--help", "Show this help message.") do
>>>      puts opts
>>>      exit
>>>   end
>>>
>>> end
>>
>> o.parse!
>>
>> if ARGV.empty?
>>  puts o
>> else
>>  # do whatever
>> end
>>
>> Kind regards
>>
>>        robert
>>
>>
>
> This works perfectly, thanks much!
>
> (I never thought to mix querying ARGV with the OptionsParser class)

When I think of it you probably also want to consider this variant:

o = OptionParser.new do |opts|
  ...
end

if ARGV.empty?
  puts o
else
  o.parse! ARGV
  # main
end

Depends on when you want to detect the "emptiness".

Btw, on_tail only determines where the option is printed when printing
usage IIRC.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/