From: dblack@...
Date: 2006-03-18T01:53:57+09:00
Subject: Re: Explanation of if __FILE__ == $0

Hi --

On Sat, 18 Mar 2006, PJ Hyett wrote:

> So I've tracked this down:
> __FILE__ is the name of the current source file
> $0 at the top level is the name of the top-level program being executed
>
> But I'm still confused as to what this if statement is accomplishing?
> It's obviously useful for something since it's used quite often. Does
> this pertain to when a script is called from another script?

Yes; if __FILE__ (the name of the current file) is the same as $0 (the
file where execution started), then you're in the startup file.
You'll often see this used in, say, a library file that usually gets
loaded from another file (so __FILE__ == $0 is false), but can also be
run standalone for the sake of running tests.


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

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