From: Kevin Jackson <foamdino@...>
Date: 2007-06-10T11:59:40+09:00
Subject: Re: using ` and the bash source command

Hi,

> What effect were you expecting to see?

This may seem fairly trivial (and it is), but I'm writing a jdk/java
switcher app as I spend a lot of time working on open source java and
I need to test on multiple jdks.  Now previously I've always opened vi
and made the changes manually, but I decided that a tiny gui program
would give me a chance to do a bit of ruby for a change, and I could
get some more experience with Gtk.

So my code essentially builds a menu of all the different jdks
installed and then when the user picks an option (eg java-gcj), the
code writes the correct JAVA_HOME out to .bash_profile ready for use

The final step was to source the .bash_profile so that I can just
choose a jdk and be immediately ready to use it

Attached the code (it's not OO at all, just a simple script):

#!/usr/bin/ruby

=begin
  jdk_switcher.rb - Ruby/Gnome2 JDK switching tool
  Copyright (c) 2007 Kevin Jackson
  This program is licenced under the Apache Software Licence 2.0
=end

require 'gtk2'

def set_java_home(java_version)
  puts "#{java_version} selected"
  `head -n-2 $HOME/.bash_profile > $HOME/.bash_profile.new`
  `echo '#Modified by
jdk_switcher\nJAVA_HOME=/usr/lib/jvm/#{java_version};export
JAVA_HOME;PATH=$JAVA_HOME/bin:$PATH' >> $HOME/.bash_profile.new`
  `mv $HOME/.bash_profile.new $HOME/.bash_profile`
  exec "/bin/bash -c 'source ~/.bash_profile;'"
  %x{/bin/bash -c ". ~/.bash_profile;"}
end

window = Gtk::Window.new
window.signal_connect("delete_event") {
  false
}

window.signal_connect("destroy") {
  Gtk.main_quit
}

option_menu = Gtk::OptionMenu.new
menu = Gtk::Menu.new
Dir.foreach("/usr/lib/jvm") do |e|
  unless e[0,1] == "."
    mi = Gtk::MenuItem.new(e)
    mi.signal_connect("activate") {
      set_java_home(e)
    }
    menu.append(mi)
  end
end


menu.show_all
option_menu.menu=menu
window.border_width = 10
window.add(option_menu)
window.show_all

Gtk.main