From: Brian Candler <B.Candler@...>
Date: 2007-03-06T23:31:40+09:00
Subject: Re: Require within a module: path question

On Tue, Mar 06, 2007 at 10:59:15PM +0900, Drew Olson wrote:
> It seems to me that if I create a module, a.rb, and a script that
> require's that module, b.rb, something interesting happens. In this
> case, my a relies on other external files in the project, so I must
> require these files within a.rb. However, I've noticed that because b
> requires module a, all the require statements within the file a.rb must
> be relative to b's location in the directory structure.

No - they just have to be relative to any of the directories in $: (the load
path array)

On my machine I get:

$ ruby1.8 -e 'puts $:'
/usr/local/lib/site_ruby/1.8
/usr/local/lib/site_ruby/1.8/i486-linux
/usr/local/lib/site_ruby/1.8/i386-linux
/usr/local/lib/site_ruby
/usr/lib/ruby/1.8
/usr/lib/ruby/1.8/i486-linux
/usr/lib/ruby/1.8/i386-linux
.

The last entry (.) means "the current directory".

So if I do "require 'a/b'" then the system will try

/usr/local/lib/site_ruby/1.8/a/b.rb
/usr/local/lib/site_ruby/1.8/i486-linux/a/b.rb
/usr/local/lib/site_ruby/1.8/i386-linux/a/b.rb
/usr/local/lib/site_ruby/a/b.rb
/usr/lib/ruby/1.8/a/b.rb
/usr/lib/ruby/1.8/i486-linux/a/b.rb
/usr/lib/ruby/1.8/i386-linux/a/b.rb
./a/b.rb

> Thus, when these
> files are stored in different places, it becomes very confusing when
> looking at file a.rb as to why the require statements don't seem to be
> relative to that file. Is this intended functionality? Have I done
> something stupid?

If you don't want to install your own module files in one of the locations
listed above, then install them in some other directory and use

  ruby -I /path/to/my/lib a.rb

to run the program; or else at the top of a.rb you can write

  $:.unshift("/path/to/my/lib")

In both cases this just adds additional entries to the load path.

HTH,

Brian.