# 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