Allowing only one instance of a script?

[Grant Edwards]

On 2005-06-23, Grant Edwards <grante at visi.com> wrote:
> On 2005-06-23, Tim Golden <tim.golden at viacom-outdoor.co.uk> wrote:
>> [Ali]
>>| 
>>| I have a script which I double-click to run. If i double-click it
>>| again, it will launch another instance of the script.
>>| 
>>| Is there a way to allow only one instance of a script, so that if
>>| another instance of the script is launched, it will just 
>>| return with an
>>| error.
>>
>> If you're on Windows, have a look at this recent thread:
>>
>> http://groups-beta.google.com/group/comp.lang.python/msg/2a4fadfd3d6e3d4b?hl=en
>
> If you're on Unix/Linux, the usual way to do this is with a
> lockfile.

You can also use a network port instead of a file.  Binding a
socket to a port is an exclusive and atomic operation.  An
advantage to the network port scheme is that the "lock"
automatically goes away if the program dies.  A disadvantiage is
that it can't contain information (date/time/PID) like a file
can.

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