From: James Adam <james.adam@...>
Date: 2006-11-08T01:10:57+09:00
Subject: Re: The way to restrict a ruby program to just once occurrence on a windows box?

You could also take a leaf out of unix tradition and simply write a
small file containing the current process ID into a temporary
directory. When your program starts, it checks for this file, and if a
corresponding running Ruby process is found then it can exit (perhaps
with a log message or something). If not, then the starting instance
would seem to be the only one.

- james

On 11/7/06, Murray Steele <murray.steele@gmail.com> wrote:
> 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
> >
> >
>
>


-- 
* J *
  ~