From: Robert Klemme <bob.news@...>
Date: 2004-02-09T18:14:58+09:00
Subject: Re: Threads for dummies


"Svend-Erik Kj�r Madsen" <sv-erik@fjernmig_stofanet.dk> schrieb im
Newsbeitrag news:40260d72$0$17636$ba624c82@nntp05.dk.telia.net...
> Hi
> Can somone please tell me howto handle threads in the code below
> <code ex>
> def start_app
> system("echo #{$passwd}|sudo -S #{$appl}"}
> $passwd.value = ''
> $appl.value = ''
> end
> </code ex>
>  Works fine, but the system(....) thing, grabs focus ontil the
application
> stops.
>
> So far Ive tried to write something like:
> <code ex >
> def start_app
> Thread.new($passwd, $appl) do
> t = Thread.current
> passwd = t[:$passwd]
> appl = t[:$appl]
> system("echo #{passwd}|sudo -S #{appl}"}
> end
> $passwd.value = ''
> $appl.value = ''
> end
> </code ex>
>
> This dosnt work
>
> What I want is to create a subprocess running the programm, and return
to
> reset the variables.

It's generally a bad idea to let the sub program reset the variables after
it is done because you can't control the point in time and that might have
all kinds of strange effects.  Better use local variables.  Two
approaches:

def start_app(appl, passwd)
  Thread.new do
    system("echo #{passwd}|sudo -S #{appl}"}
  end
end

Or, if you don't want to define a method for this, you should proceed like
this:

Thread.new($appl, $passwd) do |app, pass|
  system("echo #{pass}|sudo -S #{app}"}
end

This way "app" and "pass" are local variables and as soon as you started
the thread you can change values of those global variables to whatever you
like and they don't interfere.

Regards

    robert