From: Glenn Smith <glenn.ruby@...>
Date: 2006-11-07T23:19:48+09:00
Subject: Re: The way to restrict a ruby program to just once occurrence on a windows box?

Never mind, solved it (unless anybody knows a better way).

It's a windows app, so:

require 'Win32API'

SW_HIDE = 0
WS_OVERLAPPED = 0
WS_DISABLED = 0x08000000
WS_MINIMIZED = 0x20000000

  def already_running
    #
    # Not sure of any other way to do this.
    # Create a window with the title "i4FileProcessorHiddenWindow".
When we come to run this program again,
    # if there is already a window called
"i4FileProcessorHiddenWindow" then abort that instance.
    # In this way, only one instance of the script should run.
    #

    findwindow = Win32API.new('user32','FindWindow', ['p','p'], 'L')
    return true if findwindow.call("STATIC", "i4FileProcessorHiddenWindow") != 0

    createwindow = Win32API.new('user32', 'CreateWindowEx', ['l', 'p',
'p', 'l', 'i', 'i', 'i', 'i', 'l', 'l', 'l', 'P'], 'l')
    dwStyle = (WS_DISABLED | WS_MINIMIZED)
    cw = createwindow.call( WS_OVERLAPPED, 'STATIC',
'i4FileProcessorHiddenWindow', dwStyle, 0, 0, 0, 0, 0, 0, 0, 0 )
    show = Win32API.new('user32',  'ShowWindow', ['L', 'L'], 'L')
    show.call(cw, SW_HIDE)

    return false
  end


On 07/11/06, Glenn Smith <glenn.ruby@gmail.com> wrote:
> I'm rewriting a vb app to ruby (in about a quarter of the code!).  If I ran
> the same ruby program twice in parallel, the second instance should exit.
>
> In VB6 I could do this:
>
>              If App.PrevInstance Then Exit Sub
>
>
> Any ideas how this is done in ruby?
>
>
> Ta muchly
>
>


-- 

All the best
Glenn
Aylesbury, UK