instdir (install.rb)

    # File install.rb, line 36
    def instdir
        g = GetoptLong.new(['--install-dir', '-i', GetoptLong::REQUIRED_ARGUMENT])
        g.each { | name, arg |
    	if name == '--install-dir'
    	    return arg
    	else
    	    $stderr.puts "usage: $0 [--install-dir dir]"
    	end
        }

        begin
    	require 'rbconfig'
    	libdir = Config::CONFIG['sitedir'] + "/" +
    	    Config::CONFIG['MAJOR'] + "." +
    	    Config::CONFIG['MINOR']
        rescue ScriptError
    	$LOAD_PATH.each do |l|
    	    if l =~ /site_ruby/ && l =~ /\d$/ && l !~ /#{PLATFORM}/
    		libdir = l
    		break
    	    end
    	end
    	STDERR.puts "Can't find required file `rbconfig.rb'."
    	STDERR.puts "The 'radius' files need to be installed manually in " +
    	    " #{libdir}"
        end
        return libdir
    end