On Sun, Dec 5, 2010 at 12:19 AM, Daniel Berger <djberg96 / gmail.com> wrote:
> On 12/4/10 2:47 PM, Jim Burgess wrote:
>>
>> Hi,
>>
>> I have a FXRuby app, which is fine and dandy and does exactly what it
>> should. However, if the user, for whatever reason, decides to start two
>> instances of the app, bad things start happening.
>> My question: is there any way for my app to check if another instance of
>> itself is running before launching itself?
>
> To make sure no more than 1 instance of the script is running:
>
> gem install posixlock
> require 'posixlock'
> DATA.posixlock( File::LOCK_EX | File::LOCK_NB )

This smells like a pure UNIX solution to me (and I don't know if Ruby
can deal with the Windows POSIX subsystem, as that is something that
isn't part of the default install on Windows).

What I would do is create a file in the app's startup code (in the
temporary directories of the OSes you target, for example, since that
directory gets cleaned rather often by the OS itself), and check if
this file exists on start up.

Of course, you get a problem if your application is killed by a task
manager (so, you could write the PID of your current process into the
lock file, and check if this PID exists before you terminate your app
prematurely).

-- 
Phillip Gawlowski

Though the folk I have met,
(Ah, how soon!) they forget
When I've moved on to some other place,
There may be one or two,
When I've played and passed through,
Who'll remember my song or my face.