On 7/16/10, Ralph Shnelvar <ralphs / dos32.com> wrote:
> The following line acts differently under rdebug and ruby
>   if __FILE__ == $0

The name rdebug is ambiguous. Do you mean debug.rb, the debugger which
comes with ruby, or the ruby-debug gem? I suspect it's the latter,
since I have encountered this same bug with it.

> FXRuby has the line, above, in nearly all its sample code.
>
>
> Under rdebug, the value of $0 is, on my system,
>   F:/InstantRails-2.0-win/ruby/bin/rdebug
>
> Executing
>   ruby -rdebug UltraDedup.rb
> then the value of $0 is
>   Debug.rb
>
>
> Executing
>   ruby UltraDedup.rb
> then the value of $0 is
>   UltraDededup.rb

This is an unfortunate bug in ruby-debug. In general, ruby-debug has
more problems for me than debug.rb, so I usually jsut use debug.rb.
The reason to prefer ruby-debug is because it's so much faster.
Sometimes, this becomes very important.

>
>
> How can I change things so that
>   if __FILE__ == $0
> acts correctly in each environment?

I know of no really good solution. Typically, I manually set $0 to
__FILE__ at the beginning of a debugging session to work around this
problem (cursing all the while). I think this command is guaranteed to
do it:

  p $0=__FILE__

Tho with some versions of ruby-debug, I could leave off the p.