From: Murray Steele <murray.steele@...>
Date: 2006-11-07T23:33:24+09:00
Subject: Re: The way to restrict a ruby program to just once occurrence on a windows box?

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Is it some kind of GUI app?  I don't know what toolkit you are using, but I
do remember from my days as a wxPython jockey that the wxWidgets  toolkit
came with a api for doing exactly this: wx.SingleInstanceChecker.  I imagine
that there's a win32 API that is used to do it, and that should be available
to most other toolkits you might be using (e.g. I'm sure Java Swing has
something similar).

I imagine that such an API should be available even if it isn't a GUI app
(perhaps through Win32API) and I imagine that using this would be slightly
cleaner than doing your own version.

Admittedly this isn't much use as all I'm saying is, "yeah, there is a way
to do this" without providing much details...

Sorry

Muz

On 07/11/06, Glenn Smith <glenn.ruby@gmail.com> wrote:
>
> 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
>
>

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