From: Eric Hodel <drbrain@...7.net>
Date: 2008-04-15T18:21:44+09:00
Subject: Re: How to reliably setup require path

On Apr 14, 2008, at 16:16 PM, Joel VanderWerf wrote:
> Christian Johansen wrote:
>> I'm writing my first Ruby command line application (beyond a simple
>> script) and I'm little unsure about how to structure the  
>> application and
>> the best use of require. I've come as far as to have the following  
>> file
>> structure:
>> myapp/
>>  bin/
>>    myapp
>>  docs/ (RDOC files)
>>  lib/
>>    myapp.rb
>>    myapp/
>>      files and folders here
>>  test/ (Test::Unit tests)
>> And the application is working, but there are a few things of which  
>> I am
>> unsure:
>> The bin/myapp file is a symlink to the lib/myapp.rb file which has a
>> shebang line. This doesn't really work, because inside lib/myapp.rb I
>> have:
>> require 'myapp/file'
>> require 'myapp/module/file'
>> which doesn't make sense when running the application from anywhere  
>> else
>> than myapp/lib
>> I also tried
>> $MYAPP_ROOT = File.expand_path(File.join(File.dirname(__FILE__),
>> 'myapp'))
>> $LOAD_PATH << File.expand_path($MYAPP_ROOT)
>> Which still doesn't work because this also relies on cwd...
>> How do I work around this? What's the best practice way of making  
>> these
>> things make sense? Do you use the $RUBYLIB variable to set the full  
>> path
>> to the application? I was hoping to create the application as  
>> standalone
>> as possible, so installation will be easy.
>
>
> I'd do a couple of things differently (and I've used this pattern in  
> a number of applications with the same dir structure as yours):
>
> 1. make bin/myapp a very short ruby script instead of a symlink (if  
> you want this to work on windows, symlinks won't work anyway).
>
> 2. use unshift instead of <<, so you get precedence
>
> 3. use an ENV var instead of a global so child scripts can use it
>
> 4. use File.dirname to go up two levels instead of one, so that you  
> can use it to find non-lib files as well (images for example, or  
> other data files). Note that the expand_path call has to happen  
> before calling dirname twice.
>
> Here's the code:
>
> ENV['MYAPP_BASE'] =  
> File.dirname(File.dirname(File.expand_path(__FILE__)))
> libdir = File.join(ENV['MYAPP_BASE'], "lib")
> $LOAD_PATH.unshift libdir
> ENV['RUBYLIB'] = libdir + ":" + ENV['RUBYLIB']

The simplest way is `ruby -Ilib bin/myapp` from the root of the  
project dir.

(-I directories take precedence over RUBYLIB directories.)