From: Tim Hunter <rmagick@...>
Date: 2008-02-07T05:45:00+09:00
Subject: Re: how to say # in ruby

Gerry Ford wrote:
> Well, you sound friendly enough.

I'm very friendly. Just ask anybody.

> My second question is about the shebang line: #!
> I was surprised to find that it matters what's written here when using 
> the windows platform.  There is no env folder in the bin folder, so if 
> that's a path, then it's a path to nowhere.  What "should" the first 
> line say?

I would've guessed that it didn't matter, but I tried

#! garbage

and was also surprised to learn Ruby terminates the program with the 
message "test.rb:1: Can't exec garbage (fatal)".

So I looked at the source code. In the load_file() function in ruby.c, 
there is code that inspects the first line in the script. If it starts 
with "#!" then the line must also contain the word "ruby". If it 
doesn't, then Ruby calls execv() to run the "program" that it assumes 
follows the #!. When execv() fails, Ruby terminates the program.

If the #! is on the 2nd line, or if the first line is

#! <anything>ruby<anything>

then everything is copacetic. That's why

#! /usr/bin/env/ruby -w

works.

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