From: Matthew Harris <shugotenshi@...>
Date: 2007-12-21T18:42:11+09:00
Subject: Re: check if application exists

Al Og wrote:
> Hello everyone,
>
> I'm launching external application from my ruby script
> using %x{application_name}
>
> I want to check if such application exists before launching.
> To check it on linux I can parse "which application_name" command
> output.
>
> But what about windows platform? Is there any crossplatform solution
> exists?
>
> Regards,
> arkadi4
>   
Hi there.

You would usually check the $PATH environment variable on *nix systems, 
and %Path% on Windows.

In Ruby, that environment variable may be accessed through ENV['PATH'].  
The path is joined together by a path separator character (on Windows it 
is a semi-colon `;' and on *nix it is a colon `:').  You can get this 
separator in an OS depending way such as File::PATH_SEPARATOR.

I'm sure from here you get the idea.  You must split the path into each 
directory and perform an iterative operation, verifying the directory 
exists and if the program also exists in that directory.

-- 
Matthew Harris
http://matthewharris.org