From: Ken Bloom <kbloom@...>
Date: 2006-08-14T14:05:07+09:00
Subject: Re: [OT] sh command that ascends dir tree for executable

On Sun, 13 Aug 2006 23:01:19 +0000, Jeffrey Schwab wrote:

> Ken Bloom wrote:
>> On Sat, 12 Aug 2006 17:43:02 +0000, Jeffrey Schwab wrote:
>> 
>>> Trans wrote:
>>>> Before I do and implement this myself, want to make sure it doesn;t
>>>> already exist in some fashion: A command line utility like 'sh' but one
>>>> that will ascend the directory tree to find the executable.
>>> # Caution:  On Windows, File.executable? is roughly equivalent to 
>>> File.exist?.
>>>
>>> def find_program_hierarchically(p)
>>>      d = File.expand_path('.')
>>>
>>>      # Remove drive letter for Windows paths.
>>>      d.gsub!(/^[^\/]*/, '')
>>>
>>>      while d.length != 0
>>>          f = "#{d}/#{p}"
>>>          return f if File.executable?(f)
>>>          d.gsub!(/\/[^\/]*$/, '')
>>>      end
>>>
>>>      return nil
>>> end
>>>
>>> puts find_program_hierarchically('main.rb')
>>> puts find_program_hierarchically('nonesuch')
>>> puts find_program_hierarchically('hello.txt')
>> 
>> Yuck.
> 
> Thanks. 
> 
>> Try this simpler code:
>> 
>> require 'pathname'
>> 
>> class Pathname
>> def ancestors
>>    return [self] if self==parent
>>    return [self] + parent.ancestors
>> end
>> end
>> 
>> def find_program_hierarchically(p)
>>    dir=Pathname.getwd.ancestors.find {|d| (d+p).executable?} + p
>> end
> 
> I'm not convinced that's simpler.  It's the same number of lines, brings 
> in an extra module, is recursive, and stuffs seven distinct identifiers 
> onto a single line.  It does look nicer at first glance, though, since 
> it uses much less punctuation.

I have a habit of writing really really long one-liners.

--Ken

-- 
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/