From: Kedar Mhaswade <kedar.mhaswade@...>
Date: 2010-12-22T00:05:41+09:00
Subject: Re: debug flag being ignored

rickhg12hs wrote in post #131750:
>> I'm trying to run 'ruby -d foo.rb' and the d is either ignored or I don't
>> understand how it works.  The code just runs as if there is no -d option.
>
> "-d" sets $DEBUG to true.
>
> Does your code execute something when $DEBUG is true?
>
> For example:
>
> puts "Important intermediate value: #{my_critical_var}" if $DEBUG

I was going nuts over this.
This file:
#!/usr/bin/env ruby
puts $DEBUG

prints false with or without ruby -d (e.g. ruby -d foo.rb)

So, the shebang line comes in the way in an unpredictable manner. The 
workaround is to have export RUBYOPT=-d $RUBYOPT if you wanted shebang 
line (and the easier invocation like: ./foo.rb after chmoding it).

If you are giving your file to the interpreter directly like: ruby 
foo.rb (*and* you don't have shebang line in the file), then ruby -d 
works as expected.

Bottom line: For such a simple thing, shebang line complicates life 
(unnecessarily) at least on Linux :(

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